Plywood Handbookcanada

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certiWood Canply pwood Hdbook

www.canply.org

Over Five Decades of Service to the Plywood IndustryThe CertiWoodTM Technical Centre (formerly named the Canadian Plywood Association or CANPLY) is a non-profiindustry-funded association representing manufacturers of engineered wood products in Canada. Since the associationname change in 2005 from CANPLY to CertiWoodTM, plywood producing companies have retained the CANPLY trademar ancontinue to stamp their production with the well-nown mar. The CANPLY stamp continues to serve as an assurance tbuyers that the plywood is produced under CertiWoods exacting 3rd party quality auditing process and that it will perform ia satisfactory and predictable manner.

CANPLY plywood is manufactured by 6 companies belonging to CertiWoodTM (member companies) operating in BritisColumbia and Alberta. Together, these companies operate 9 mills and produce over 90% of all structural, construction anindustrial plywood manufactured in Canada. Member company plywood production is about 1.7 billion square feet (3/8" basis

annually. Approximately 90% is shipped to marets across Canada. The balance is exported to some 28 countries, amonthese: the United States, Japan, the United kingdom and Germany.

Originally founded in 1950, CertiWood has a long history of service to its member companies and their customers. TodayCertiWoods purpose is, To provide cost-effective certification, quality auditing and testing services to Canadian engineeredwood products manufacturers.

CERTIFICATION MARkSThe registered certification mars shown below appear on CANPLY EXTERIOR Douglas Fir plywood (DFP)CANPLY EXTERIOR Canadian Softwood plywood (CSP) and CANPLY EXTERIOR Poplar Plywood manufactured by oumembers to meet the requirements of CSA O121, CSA O151 or CSA O153. CertiWood also certifies its Members productto meet US and other international standards (see below).

Licensed mill number of the CertiWood member

Indicates that this product is manufactured under CertiWoodsQuality Certification Program.

Indicates that the plywood has been manufactured by a member of CertiWood

Indicates a completely waterproof glue bond

Indicates species designation: DFP (Douglas Fir plywood),

CSP (Canadian Softwood plywood), Aspen or Poplar plywood

Indicates the CSA standard governing manufacture

Indicates that the plywood has been manufactured by a CertiWood member aquality certified

Indicates a completely waterproof glue bond

Panel grade

Indicates species designation: DFP (Douglas Fir plywood),

CSP (Canadian Softwood plywood), Aspen or Poplar plywood

Licensed mill number of CertiWoodmember (BC xxx, AB xxx).

This symbol identifies the patented tongue and groove profiles of CANPLY T&Gproducts formerly nown as COFI FLOOR & COFI ROOF.

Face stamp on COFI FORM Douglas Fir plywood for concrete formwor.

PLYCO CANADA BC xxx CANPLY EXTERIOR CSP GRADE

Edge Stamp on CANPLY EXTERIOR Plywood (Sanded and Unsanded grades)

INTERNATIONAL CERTIFICATION MARkS:

Face Stamp on CANPLY EXTERIOR Plywood (Unsanded grades)

uSa

Japan EuropEan union


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CANPLY EXTERIOR PLYWOODInformation in this brochure pertains toCANPLY EXTERIOR Douglas Fir plywood,CANPLY EXTERIOR Canadian Softwood

plywood and CANPLY EXTERIOR Poplarplywood. These products are manufacturedin accordance with Canadian Standards

Association Specifications CSA O121Douglas Fir Plywood, CSA O151Canadian Softwood Plywood orCSA O153 Poplar Plywood by companieswho are members of CertiWood. CANPLYcertification stamps, shown opposite, are onall Canadian Plywood products meetingCertiWoods Quality Certification Program.

Panel ConstructionCANPLY EXTERIOR plywood is anengineered panel built up from sheets ofveneer glued together with a waterproofresin adhesive. The thicness andorientation of the plies determine theperformance of the panel. The veneers areunited under high temperature and pressurewith a resin glue that is completelywaterproof, maing the plywood suitable for

use under conditions of extreme exposure tomoisture.

SpeciesPlywood mared CANPLY EXTERIOR may bedesignated as Douglas Fir (DFP), CanadianSoftwood (CSP), Aspen or Poplar plywood.

CANPLY EXTERIOR Douglas Fir plywood ismanufactured with faces of Douglas Firveneers. The inner plies and some bacsmay be of veneers of the selectedconiferous species shown in Table 1. Thepermissible species for CANPLY EXTERIOR

Canadian Softwood plywood are alsoshown in Table 1. For a complete list ofallowable species in CANPLY Poplarplywood, please refer to the standard CSAO153.

ManufactureThe manufacturing process begins byconveying selected logs to a barer wherethey are rotated against a steel claw to stripthe bar and debris from the log surface.The logs are then cut into peeler blocs. Inconformance with todays standards ofsustainable forestry, the logs we harvest are

from secondary growth forests and average25cm (10 ") in diameter.

After conditioning, peeler blocs are movedto a lathe where they are set in the chucs byan automatic charger. Using laser sensors,the bloc is imaged and automaticallyaligned in the lathe to maximize veneerrecovery. As the bloc is rotated, the honedsteel blade of the lathe is brought in contactwith it, peeling a continuous sheet of veneer.

As veneer is produced it is directed tosemiautomatic clippers that scan the veneer,remove oversize defects and cut it to widthfor sorting and stacing. Standard widthsare staced automatically and randomwidths manually. Veneer is passed throughmoisture sensors and segregated bymoisture content. Segregation is necessaryas veneer with different moisture contentsrequires different drying cycles.Veneer is dried in steam or gas-heatedovens at temperatures ranging from 160 to200 C. The speed at which the veneermoves through the dryer depends on thethicness of the veneer and its moisturecontent.

After passing through the dryer, electronicmoisture detectors mar all veneer in excessof the moisture content allowed for gluingThe veneer is staced separately and laterre-dried.

After dying, the veneer is optically scannedimaged on a computer and further sortedaccording to grade. Narrow widths may bedirected through a composer where edgesare cleaned, squared and welded into

continuous sheets and clipped into standardwidths.

Substandard veneer with oversizeimperfections is either discarded orchanneled to patching machines where theimperfections are neatly replaced withsound wooden patches.

Sound veneer then moves to the gluespreader or automatic lay up line where theveneers are uniformly coated with resin glueand laid at right angles to the adjacentveneers. This cross-lamination accounts foplywoods exceptional two-way strength and

dimensional stability.

After lay up, the veneer sandwiches go tothe hot press, the ey operation in themanufacturing process. Here, dependingupon the thicness of the plywood panelone or more sandwiches are loaded intoeach press opening. The press is thenhydraulically closed and the panelssubjected to a temperature of 150 C and apressure of 1.38 MPa which cures the glueThe resin glue, when cured in the hot press,produces an inert water-proof bond.

After removal from the hot press, trim saws

cut the plywood panels to the requireddimensions, usually 1220 mm by 2440 mm(4' x 8'). Panel edges and panel ends aretrimmed in consecutive operations.

Panels are then graded as sheathing oselected for further finishing. Panels to beproduced as sanded grades pass to asander where face and bac aresimultaneously sanded smooth.

Any minor imperfections remaining in theface and bac veneers may be repaired withwood inlays or synthetic filler before thepanels are finally graded by silledinspectors.

All grades of plywood produced byCertiWood members are then stampedwith the registered certification marCANPLY EXTERIOR before leaving the mill.

Most wood waste during manufacture iscollected and burned in high efficiencyburners to be converted into heat oelectricity, offsetting most of the mill's energyneeds.

3 certiWood Canply pwood Hdbook

ContentsCANPLY EXTERIOR Plywood

Plywood Grades and Products

Sizes and Thicnesses

Woring with Plywood

Fasteners

Glues and Gluing

Floor Sheathing

Wall Sheathing

Roof Sheathing

Permanent Wood Foundations

Concrete Forms

Plywood in Farm Structures

Plywood Structural Assemblies

Finishing

Preservative Treatments

Fire Retardant Treatments

Specifying Plywood

page....................3

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Plywood

Handbook


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Tbe 1. Secies ermitted i Canply Exterior pwood

Steps in the manufacture of plywood

* Permitted on the backs of 6, 8, 11 and 14 mm Good One Side DFP

** Not permitted in sheathing grades

1. The log emerges from the barker after havingbeen stripped.

2. Logs are conditioned using steam or hot waterto improve peel qualit

3. At the lathe, a sharp blade peels the log, nowcalled a block, into a continuous sheet of veneer.

4certiWood Canply pwood Hdbook


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7. After pressing, the panels are trimmed,squared, and selected for grade.

6. The veneer sandwiches are subjected toheat and pressure in the hot press untilthe glue is cured.

8. Finished panels are carefull inspectedand graded.

5. Veneers are coated with waterproof glueand laid up into sandwiches.

9. CertiwoodTM qualit control inspectorscheck finished panels in inventor.

10. Plwood samples, selected at random,are tested at the CertiWood TechnicalCentre.

11. Other samples are subjected to the boilingtest specified b the CSA.

12. Some samples are subjected to vacuum-pressure tests.

4. Green veneer is dried in steam or gasheated ovens.

13. Samples are shear tested to determine the strength of the glue bond. 14. Panels that meet our stringentrequirements are identified with the CertiWoodCertification Mark.


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PLYWOOD GRADES AND PRODUCTSCertiWood members produce a widerange of CANPLY EXTERIOR plywoodgrades and products. Grade names ingeneral are based on the quality of theveneers used for the face and bac of thepanel. CANPLY EXTERIOR plywood gradesare shown in Table 3. A list of proprietaryCANPLY Exterior Plywood products is givenin Table 4.

Overlaid PlywoodPlywood is also manufactured with overlayswhich improve the appearance anddurability of the panel. The overlays arebonded to the face veneers of the plywoodby heat and pressure. This process sealsthe overlay to the wood to form aninseparable bond stronger than the wooditself. The resin content of the overlaydetermines whether the final product iscalled Medium or High Density Overlaidplywood.

Medium DensityThe resini m p r e g n a t e dface presents asmooth uniformsurface intendedfor high qualitypaint finishes.Some evidenceof the underlyinggrain mayappear. Overlay is produced in a naturalbuff colour and certain other colours.

Popular uses for Medium Density Overlaid

plywood are flat, lap and bevel sidings; andsundecs, soffits and accent panels inresidential construction. Other applicationsinclude boats, highway signs and manyother commercial uses.

High DensityThe resin impregnated face is hard, smooth,and chemically resistant. No further finishingwith paint or varnish is necessary. Theoverlay is usually produced in a whitishsemi-opaque colour but other colours maybe used by manufacturers for identification.Major uses for High Density Overlaidplywood include fine finish concreteformwor, storage bins, liquid tans andsigns.

Mill SpecialtiesMill specialties are variations of the plywoodgrades and products shown in Tables 3 and4. These panels are manufactured by anumber of member companies andmareted under their own brand names. Millspecialities include patterned, overlaid,textured, brushed, embossed, striated,grooved and pre-finished panels fordecorative use.

Tongue and Groove PlywoodT&G plywood has a factory-machinedtongue along one of the long edges and agroove along the other. T&G panelsinterloc to ensure the effective transmissionof loads across joints, eliminating differentialdeflection between adjoining panel edgesand maing the use of blocing or H-clips atlongitudinal joints unnecessary.

CertiWood members manufacture twopatented T&G panels, under one name EASY T&G. These panels have T&G edgesspecifically designed for roof and floorsheathing. Panel installation is fast and easywith these patented edge profiles, exclusiveto CertiWood members

Concrete Form PanelsAll plywood bearing the registeredcertification mar CANPLY EXTERIOR issuitable for concrete formwor because it ismanufactured with waterproof glue.

CANPLY EXTERIOR DFP isavailable in sanded andunsanded grades and in specialhigh strength constructions.CANPLY EXTERIOR CSP isavailable in unsanded gradesonly. Sanded grades produce asmooth, wood grain finish valuedby many architects. Unsandedgrades are suitable for formworwhere the appearance of the

concrete is less important such as in sub-surface foundations.

CANPLY EXTERIOR plywood is also

available edge sealed, treated with chemicalrelease agents, and with resin impregnatedcellulose fibre overlays. Overlays producethe highest quality concrete finish. They alsohelp protect the plywood from oil and water,simplify form stripping and extend theservice life of concrete forms.COFI FORM PLUS and COFI FORM arespecial high-strength constructions of DFP

panels designed specifically for use asconcrete formwor. These panels aresignificantly stiffer than standardconstruction of DFP in wet serviceconditions because of stricter limits onspecies and ply thicnesses duringmanufacture. COFI FORM PLUS is thestiffest Douglas Fir panel manufactured byCertiWood members (Table 4).

SIZES AND THICKNESSESCANPLY EXTERIOR plywood is manufacturedin a size of 1220 mmby 2440 mm, the metricequivalent of the familiar 4 ft by 8 ft panel. Itis also available in a metric size of 1200 mmby 2400 mm (Table 2). Net face widths foEASY T&G are given in Table 2.

CANPLY EXTERIOR plywood is manufacturedin a range of thicnesses from 6 mm to over30 mm as shown in Table 2.

NOTE: CANPLY EXTERIOR plywood panelsare available in additional sizes andthicknesses on special order.


EaSy T&G - Foor rofie

EaSy T&G - Roof rofie

Thickness Size

LengthsAvailable up to 2500 mm

WidthsAvailable from 600 mm to 1250 mm

For EASy T&G panels, deduct 15mm from the nominal width for netface coverage.

All thicknesses are metric, but some approximateimperial dimensions, e.g. 6 mm (1/4 in.)

Available as square edge or withEASy T&G edge.

20.5 mm

22.5 mm

25.5 mm

28.5 mm

31.5 mm

6 mm8 mm11 mm14 mm17 mm

19 mm

21 mm

24 mm

27 mm

30 mm

Tbe 2. Sizes d Thickesses of Canply EXTERIOR pwood

7.5 mm9.5 mm11 mm

12.5 mm

15.5 mm

18.5 mm

Sheathing and

Select Grades

Sanded Grades


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Grade*

Good Two Sides

(G2S)

Sanded

Good One Side

(G1S)

Select -

Tight Face

(SEL TF)

Select

(SEL)

Sheathing

(SHG)

High Density

Overlaid (HDO)

Medium Density

Overlaid (MDO)

MDO 1 Side

MDO 2 Sides

Face

A

A

B***

B

C

B***

C***

C***

Inner

Plies

C

C

C

C

C

C

C

C

Back

A

C

C

C

C

B***

C

C***

Characteristics

Sanded. Best appearance both faces.

May contain neat wood patches, inlays

or synthetic patching material.

Sanded. Best appearance one side

only. May contain neat wood patches,

inlays or synthetic patching material.

Surface openings shall be filled and

may be lightly sanded.

Surface openings may be filled and

may be lightly sanded.

Unsanded. Face may contain limited

size knots, knotholes and other minordefects.

Smooth, resin-fibre overlaid surface.

Further finishing not required

Smooth, resin-fibre overlaid surface.

Best paint base.

Typical Applications

Furniture, cabinet doors, partitions,

shelving, concrete forms and opaque

paint finishes

Where appearance or smooth sanded

surface of one face is important.

Cabinets, shelving, concrete forms.

Underlayment and combined subfloor

and underlayment. Hoarding.

Construction use where sanded

material is not required.

Roof, wall and floor sheathing.

Hoarding. Packaging. Construction

use where sanded material is notrequired.

Bins, tanks, boats, furniture, signs,

displays, forms for architectural

concrete.

Siding, soffits, paneling, built-in

fitments, signs, any use requiring a

superior paint surface.

Product

Standard**

DFP

CSP

DFP

CSP

AspenPoplar

DFP

(limits on

thickness

and

species of

face and

inner plies)

Product*

EASY T&G

ROOF

EASY T&G

FLOOR

COFI FORM

PLUS

and

COFI FORM

SHG

or

SEL

SHG

SELSEL TF

SEL

G1S

G2S

SPECIALTY

HDO

MDO

Characteristics

Milled with patented edge profile for easy

installation and edge support without H-clips

Milled with a patented edge profile for fast,

easy installation.

Special construction Douglas Fir panels

with greater stiffness and strength providing

improved properties particularly in wet

service conditions. Available in regular

sanded and unsanded grades and speciality

grades with resin-fibre overlays. Also

available with factory-applied release agent.

Typical Applications

Roof sheathing and decking for

residential, commercial and industrial

construction.

Floor and heavy roof sheathing for

residential, commercial and industrialconstruction.

Concrete forms and other uses where

wet service conditions or superior

strength requirements are encountered.

All grades and products including overlays bonded with waterproof resin glue.For complete veneer and panel grade descriptions see CSA O121 (DFP), CSA O151 (CSP) and CSA O153 (Poplar).Indicates all openings are filled.

******

Table 3. CANPLY EXTERIOR Plywood Grades

Table 4. CANPLY Exterior Plywood Proprietary Products

Product**

DFP

Poplar

DFP

DFP

DFPAspenPoplar

CSP

DFP

Aspen

Poplar

CSP

DFP

Aspen

Poplar

CSP

Veneer Grades**

Grades**

CSP

CSP

DFPAspenPoplar

DFPAspen

Poplar


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WORKING WITH PLYWOODStoring and HandlingPlywood, lie any other panel product,requires proper handling and storage.Despite its sturdy cross-laminatedconstruction, face veneers, panel edges andpanel corners are vulnerable to damageand should always be protected.

Plywood is manufactured at a low moisturecontent and while small changes in moisturecontent will not appreciably affect itsdimensions, large changes should beavoided since they may encouragechecing of the face veneer with consequentimpairment of its qualities as a paint base. Itis good practice to store plywood which is tobe used for interior finish under conditionsthat approximate those it will experience inservice.

Points to watch when handling plywood are:

1. Store plywood panels flat and level.2. keep finish faces inward and cover

stacs to protect from bumping andabrasion.3. Protect panel edges and corners.This is especially important withtongue and groove plywood.4. Carry panels on edge (always beingcareful not to damage faces, edgesand corners).5. When plywood is used as a finishingmaterial, deliver to job-site at the lastpossible moment.6. Protect panels from sunlight, water orexcessive humidity.

SawingHand sawingFor handsaw wor, panels should be sawnface (good side) up with the angle betweensaw teeth and panel surface as flat aspossible. This prevents face veneersplintering. Generally, an 8 or 10 pointcross-cut saw or a 10 point panel saw givesthe best results.

Hand Power sawingA sharp carbide tip combination blade set toprotrude no more than 12.5 mm through thepanel and firm panel support will giveexcellent results with a hand power saw.Panels should be sawn face down.

Table Power sawingPanels ept face up on a table power saware cut cleaner. A combination blade filedwith less than normal hoo is best for mostwor. The blade should be set to protrudeno more than 12.5 mm. In general, a bladeof 250 mm diameter or more wors best. Atable extension will help in handling full sizedpanels. When using a radial arm saw, theorientation of the plywood panel will dependon the type of cuts being made. The

instruction manual accompanying the radialarm saw should be consulted.

DrillingHand brace and bit, power drill or drill pressall wor easily with plywood. Holes of largediameter are best cut with a brace andexpansion bit rather than with a high-speeddrill. For power drilling, spur bits give goodresults. Reversing the panel as soon as the

bit point is through and completing the cutfrom the other side will ensure a clean cutwithout splintering.

Small holes are readily cut with either handor power drills. As a general rule, the largerthe hole the slower the drill speed.

Clean cuts can be obtained with all methodsof drilling, if the panel has firm support andis baced with scrap wood to preventsplintering.

RoutingRouters can be used to V-groove, shiplap orrebate edges of panels. Special bits areavailable for moulding and chamfering. Usesharp bits and wor carefully across panel.Deep cuts in panel edges should be madein two stages. For specific instructions, seerouter manufacturers literature.

BendingPlywood panels can easily be bent when dryinto mild simple curves. Table 5 gives drycold bend radii for the most commonplywood thicnesses. As shown in the table,plywood can be bent more sharply when the

bend is perpendicular to the direction of theface grain. These radii are based on panelsselected at random with no regard todefects such as nots, patches and shortgrain. Without selection, a small percentageof panels bent to these radii may beexpected to brea. To obtain smaller radii,i.e. sharper curves, the panels must besoaed or steamed.

Saw-erfing the bac of the panel to mae itbend more easily is not recommended if theplywood is to be used structurally.Compound curves are virtually unobtainablewith a single plywood panel and should notbe attempted.Edge Finishing

Planes used on plywood edges are woringon grain that goes in both directionsbecause of cross lamination of the plies. Fothis reason a sharp plane with shallow set isrecommended. A light jac plane will worwell on most jobs and planing in from theends towards the centre helps prevent theends from splintering.

Power tools will help get a smooth edge. A

power saw with a carbide tip blade canproduce a smooth edge if the first cut ismade more generous than is necessary andthe edge is then cut to size with a hollow-ground blade. With a jointer it is best to feedthe wood into the jointer head slowly. With adisc sander, feed the panel slowly againstthe sander at a slight angle so that the areaof edge contact is on the downward side ofthe rotating disc.

SandingWhen finish-sanding the panel face, worwith the grain using even pressure and

regular stroes. Use fine sandpaper for finaeasing and smoothing the edges and forrubbing down between coats of paint.

FastenersPlywood can be fastened to framingmaterials and other materials can befastened to plywood with a number ofdevices such as nails, staples, screws, boltsclips, and glue. Of these, nails, staples, andglue are the most commonly used.

NailsNails are available in a variety of lengths

diameters, heads points, shan styles andcoatings. In Canada, nails are specified bylength and the diameter of the wire used intheir manufacture.

For most construction uses, common nailswill be satisfactory. Where greaterwithdrawal resistance is required, such as insubflooring and underlayment nailing, ringthread, spiral or annular grooved nailsshould be used. Coated nails are nogenerally used with plywood; galvanizednails usually hold better and are less liely tocause staining if the plywood is exposed tothe weather.The length of nail for a specific purpose isdetermined by the thicness of plywood


Plywood

Thickness (mm)

6, 7.5

8, 9.5

11, 12.5

14, 15.5

18.5, 19

20.5

Bending Axis Parallel

to Face Grain (m)

0.7

1.0

2.4

3.6

4.8

5.8

Bending Axis Perpendicular

to Face Grain (m)

1.5

2.4

3.6

4.8

6.0

7.0

Tbe 5. Cod Bed Rdii

These radii are theoretical values onl and have not been verified experimentall.


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through which it must be driven. Table 6gives recommended nail lengths for thethicness of sanded plywood used in finishcarpentry wor and Table 7 gives nail lengthsfor use with unsanded plywood. Nail lengthsfor the thicnesses of plywood used insheathing applications are found in thesheathing tables.

StaplesStaples are similar in nature to nails and are

often used interchangeably. Staple sizesconforming to the requirements of theNational Building Code of Canada forplywood sheathing and subfloor attachmentare given in Table 7.

ScrewsScrews are primarily employed to fastenplywood used in finish carpentry wor,cabinetry, displays and boat building. Screwsizes for the most commonly usedthicnesses of plywood together with thediameters of the screw shan clearance andpilot holes are given in Table 8.

Screws may be counter-sun but careshould be taen to avoid breaing thesurface grain of the plywood panel.

In general, sheet metal or drywall screwshold better. Flathead screws set flush havemore holding power than round-headscrews of the same size. Under round headscrews, a washer will give extra strength.

Grommets and InsertsMetal grommets and inserts are employedwhen plywood is used for removable panels.Several types are manufactured for thispurpose.

1. Grommet is fitted with countersun holdand crimped to form socet forremovable wood screw.

2. Grommet designed for round headscrew has slotted hole for paneladjustment.

BoltsBolts have only limited use in plywood

construction. Bolt holes should be 2 mmlarger than the bolts. A tight fit requiringforcible driving of the bolts is notrecommended. With common bolts, awasher or metal plate or strap should beinserted between the plywood and the bolthead and between the plywood and the nut.Nuts should be tightened snugly but not soas to crush the wood under the washer, plateor strap.

1. Plow bolts have flush heads with fins toprevent turning.2. Carriage bolts normally are more usefulwith plywood than common bolts.3. The speed nut system is a bolt with aself locing sheet metal nut.

H-ClipsH-clips are panel edge supports in lieu of

blocing. They are used to reducedifferential deflection between adjoiningpanel edges. H-clips should be spaced asfollows:

One at midpoint for supports up to 600 mmon centre.Two at 1/3 points for supports 601 to 1000mm on centre.Three at 1/4 points for supports more than1000 mm on centre.

Using EASY T&G panels eliminates the needfor H-clips, and prevents differentiadeflection between adjoining panel edges.

Plywood

Thickness (mm)

6, 8, 11

14

17, 19

Nail Length

(mm) (in.)

38

38

51

51

1

1

2

2

Nail

Type

Casing or Finishing

Casing

Finishing

Casing or Finishing

Tbe 6. nis for Sded pwood used i Fiish Cretr

Plywood

Thickness

(mm)

7.5 and 9.5

12.5 to 18.5

20.5 to 25.5

Nail Length

Common

(mm) (in.)

Staple Length

(mm) (in.)

Ring Thread

(mm) (in.)

51

51

57

2

2

2

45

45

51

1

1

2

38

51

NA

1

2

NA

Maximum

Spacing

150 mm on centre along

edges and 300 mm along

intermediate support

Tbe 7. nis d Stes for Usded pwood

PlywoodThickness

(mm)

6

7.5 to 9.5

11 and 12.514 and 15.5

17 to 20.5

Screw Size

(mm)

19

25

3238

38

(in.)

1

11

1

Shank Clearance Pilot Hole

(mm)

3.6

3.6

3.64.4

4.8 or5.6

(in.)

9/64

9/64

9/6411/64

3/16 or 7/32

(mm)

1.6

1.6

1.62.0

2.4 or2.8

(in.)

1/16

1/16

1/165/64

3/32 or 7/64

(No.)

6

6

68

10 or12

Tbe 8. Screws for pwood

1. Staples shall not be less than 1.6 mm in diameter or thickness with not less than 9.5 mmcrown driven with crown parallel to framing.

2. All nails should be long enough that no less than half their length penetrates into thesecond member.

H-Ci

Counter sink

Shank clearance

Pilot hole

1 2

1 2 3


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GLUES AND GLUINGGluesGlue is playing an increasingly importantrole in plywood construction, both innonstructural applications such as flushpanel doors, furniture, cabinets and built-insand in structural uses such as web beams,stressed sin panels and similar plywoodstructural components.

Because of the many developments inrecent years in the field of wood adhesives,and the varied conditions of service underwhich glued wood products are expected toperform satisfactorily, the selection of aproper adhesive is important and issometimes a complex problem. Thefollowing notes on the most common typesof glues in general use today should helpmae the selection of a suitable glue for aspecific job somewhat easier. It is importantto note that plywood treated with woodpreservatives or fire-retardants is difficult toglue. Also, if the wood is to be treated after

gluing, the choice of adhesives is severelylimited.

Casein glue is one of the older woodworingglues and is still readily available in powderform. When mixed with water it forms a glueof moderately high dry strength andmoderate resistance to water, dampatmospheres and intermediatetemperatures. Casein is generally appliedand pressed at room temperature. It is notrecommended for exterior exposure and isused primarily for laminating structuraltimbers for interior use.

Contact and rubber-based glues - other thanthose elastomeric construction adhesivesdeveloped specifically for field-gluedplywood subfloors (see page 13) andaffixing plywood wall paneling to studs andstrapping - are not suitable for structuraluses. One of the main disadvantages ofthese types of glue is that their dry strengthsare generally lower than those ofconventional wood woring glues and thejoint tends to creep under prolongedloading, losing its original configuration.This joint deformation remains even after theload is removed.

Contact adhesives are developed forbonding two surfaces together without theuse of clamps. Unlie many conventionalwet bonding glues, contact adhesives areapplied to each surface to be bonded,allowed to dry, then joined together withpressure. The two dried adhesive coatingsfuse together to form a uniform bond ofimmediate strength. Generally speaing,the higher the pressure, the more uniformthe bond will be.

Common uses for contact adhesives involvethe bonding of non-porous materials to

themselves or other non-porous materialsand include gluing hard or textured surfacedmaterials such as metal, high density plasticlaminates, vinyl and other fabrics to plywoodsurfaces.

Polyvinyl acetate glues, often called whiteglues, are valuable for non-structural interioruses such as assembling flush panel doors,cabinets and furniture. They are notrecommended for exterior exposure

because they are inherently elastic and havelow resistance to heat and moisture. Theglue joint also tends to creep under externalloads and with dimensional changes in thewood caused by changes in moisturecontent.

Synthetic resin adhesives now surpass mostof the older glues in importance for bondingplywood.

Urea resin adhesives, available in drypowder or liquid forms, are used extensivelyfor furniture, cabinet and door construction,and similar general assembly wor. They

are also used in some areas of marineconstruction where the joint is not subject toexcessively high temperatures and highhumidity conditions. In general, urea resinsare high in both wet and dry strength,moderately durable under damp conditions,and have moderate to low resistance totemperatures above 50 C.

Resorcinol, phenol-resorcinol and phenol-formaldehyde resin adhesives, similar to thetype of thermo-setting glue used to maeplywood, are required for gluing plywoodand lumber into products that mustwithstand stress and exposure to the

elements. Such uses include marine worand plywood structural components such asbeams and stressed sin panels. For suchhigh strength uses a glue must developshearing stresses between the two surfacesbeing joined and therefore should bestronger than the wood itself in shear. Thesethree types of adhesives are high in both wetand dry strength, very resistant to moistureand damp conditions, and more resistantthan wood itself to high temperatures.

Epoxy resins are used for more specializedapplications such as bonding metalsplastics and some masonry materials tothemselves and to plywood. Their use inwood-to-wood bonding is limited since theirpermanence has not been adequatelyestablished. Epoxy resins are mareted intwo parts, resin and curing agent, for mixingat the point of use.

Of invaluable assistance to the glue user is

the technical assistance provided byadhesive manufacturers. Many reputableglue manufacturers maintain staffs oftechnically trained personnel willing to assistthe glue user in the selection and use of thetype of adhesive best suited to jobrequirements.

NOTE: To achieve the optimum glue bondbetween members it is imperative that theglue manufacturers recommendations inregard to wood moisture content, shelf lifepot life, working life, mixing, spreadingassembly time, time under pressure, andambient temperature be followed.

GluingGluing pressure can be applied tosecondary gluelines (i.e. gluelines other thanthe primary gluelines used in themanufacture of the plywood itself) by manymethods, including weights, pressesclamps and nails. Whatever the method, ishould be capable of exerting a pressure onthe glueline of 0.7 to 1 MPa.

Weights, presses and clamps are oftenimpractical for many gluing operationsparticularly in the fabrication of large

plywood structural assemblies. In suchcases, glueline pressure may be developedby nails - a technique nown as nail-gluing.Nail sizes and spacings for variousthicnesses of plywood are given in Table 9and are suggested as a guide to nail-gluingNail spacings recommended for nail-gluingtechniques are closer than thoserecommended for field glued sub-floorsbecause in the former the nails are used todevelop uniform pressure along the glueline


Plywood

Thickness (mm)

6 to 9.5

11 to 20.5

Nail Type

Common

Common

Nail Length

(mm) (in.)

38

51

1

2

Nail Spacing

Nails spacing shall not exceed 75 mm oc

along each row for plywood up to 7.5 mm

thick or 100 mm oc for plywood 12.5 mm

and thicker. One row of nails shall be

used for each 50 mm width or part

thereof of contact area to be glued.Rows

shall be spaced such that the distance to

the edge of the contact area is

approximately half the distance between

rows. Nails in adjacent rows shall be

staggered to provide even glueline

pressure and to reduce the danger of

splitting the lumber.

Tbe 9. Guide to ni Guig


11/28

so that the adhesive can perform as astructural fastener whereas in the latter, theelastomeric glue serves primarily to stiffenthe subfloor and prevent movement thatmay cause floor squeas.

SHEATHING, SIDING AND PANELINGFloor SheathingGeneral

CertiWood EXTERIOR plywood providesan ideal floor beneath resilient flooring andcarpeting. Plywood goes down flat andstays flat for a smooth, uniform surface.When exposed to moisture duringconstruction, some swelling may occur, butit is substantially less than panels made withparticles, strands or wafers. Also, when itdries it returns to its original thicness, thuseliminating the need to sand the jointsbefore applying the next layer. EASY T&Gplywood panels may be used to furtherreduce labour and material costs byeliminating the need for costly blocing atpanel edges.

Plywood panels for subflooring and singlelayer subflooring should be applied with facegrain perpendicular to supports and with jointsparallel to joists staggered. A 2 mm gapshould be left between all square edges ofadjacent panels. EASY T&G Floor is designedto butt at the tip of the tongue leaving a 1 mmgap on the face and underside.

To ensure the best possible performance,plywood floors should be protected from

rain and snow shortly after installation toprevent excessive moisture picup.

Where water permeable finished flooring isused in bathrooms, itchens, publicentrance halls and laundry areas, suchflooring shall be installed over a membranewith a water permeability not exceeding18 ng/Pasm2

SubflooringFor subflooring that does not come intodirect contact with floor finishing materialand is used under plywood underlayment,hardwood flooring or concrete, Sheathing

grade plywood is suitable (see table 10).

Single Layer SubflooringEASY T&G plywood or square-edgeplywood with edges supported by blocingcan be applied to floor joists forming a singlelayer subfloor. Minimum plywoodthicnesses for various support spacingsand finish floorings are given in Table 10Select grade plywood is recommended forsingle layer subfloors intended for use undermost carpeting.

Single layer subfloors for use under resilientfloor finishes such as linoleum, rubber, andsynthetic sheets or tiles, and some types ofglued-on carpets which normally require theuse of underlayment, are usually referred toas combined subfloor and underlaymentThis type of subfloor is recommended onlyfor prefabricated structures or forapplications where panels are fully protectedagainst damage and moisture before andafter installation and is not permitted for useunder ceramic tiles applied with adhesive18.5 mm Select or Select Tight Face cleaned& sized plywood is recommended forsupport spacings up to 407 mm.

For best performance, elastomeric glueshould be applied between plywood andsupports and into T&G profiles beforenailing with annular grooved nails. Finanailing should be left until the finishedflooring is to be laid, at which time theplywood should have dried to theapproximate conditions that will exist in thestructure during occupancy. The surfaceshould be prepared as recommended bythe floor covering manufacturer.

UnderlaymentSelect or Select-Tight Face grades of

7.5 mm or 9.5 mm plywood, or speciaunderlayment panels made by severaCertiWood members, are recommendedfor use as underlayment under resilient floorfinishes such as linoleum, rubber andsynthetic sheets or tiles, ceramic tiles andthose types of glued-on carpets for whichthe manufacturer recommends the use ofunderlayment. For ceramic tiles applied withadhesive, 11 mm thic underlayment isrequired where supports are spaced widerthan 300 mm on centre.

Underlayment panels should not be installeduntil wood subfloors, concrete, plaster andlumber framing have dried to theapproximate conditions that will exist in thestructure during occupancy. Alsounderlayment panels should be allowed toacclimatize in room conditions. To achievethis, it is recommended that the panels beplaced separately on edge around the roomfor a minimum of 48 hours prior toinstallation of the finished floor.

11

Plywood

Designation

DFP,CSP,

Aspen

or

Poplar

DFP,

CSP,

Aspen

or

Poplar

300

12.5

12.5

12.5

12.5

18.5

400

12.5

15.5

12.5

15.5

18.5

480

12.5

15.5

NR

15.5

NR

600

12.5

18.5

NR

18.5

NR

800

NR2

NR

NR

20.5

NR

End Use

Subflooring with panel edges not

supported:

a) Under matched softwood flooringnot less than 19 mm thick laid at right

angles to the joists

b) Under matched hardwood flooring

not less than 7.9 mm thick laid at right

angles to the joists

c) Under separate panel-type underlay

not less than 6 mm thick or with concrete

topping applied to subfloor

Single layer subflooring with panel edges

supported by blocking or tongues and

grooves:

a) Under carpeting

b) Under resilient floor finishes3

Spacing of Supports (mm)

Plywood Thickness (mm)

Tbe 10. Miimum Thickess of Canply EXTERIOR pwood dniig Schedue for Subfoorig

Plywood

Thickness (mm)

12.5, 15.5, 18.5

20.5

Nailing Schedule for Subflooring

Size and Type

51 mm (2 in.) Common or

45 mm (1 in.) Annular grooved



Maximum Nail Spacing

150 mm around perimeter and

300 mm along intermediate

supports

Recommendations suitable for residential floors where the National Building Code stipulates the design liveload does not exceed 2.4 kPa. Reduced support spacing and/or greater thicknesses ma be necessar fornon-residential construction.

1.Plywood shall be applied with face grain perpendicular to supports. 2. NR - Not recommended. 3.When resilient flooring is applied directly to plywood subfloors, thesubfloors shall be fastened to supports using annularly grooved nails and elastomeric glue should be applied between plywood and supports and into T&G profiles.4.Not applicable where flooring consists of ceramic tiles applied with adhesive.

4

certiWood Canply pwood Hdbook


12/28

Underlayment panels should be laid at rightangles to subflooring panels with joints inunderlayment staggered and offset at least200 mm from joints in subflooring, and withends and edges butted to light contact.

Unless specified otherwise by themanufacturer, underlayment panels shall benailed or stapled every 100 mm around theperimeter (10 mm to 15 mm from edge), andevery 150 mm throughout the rest of the

panel. Use 25 mm ring grooved underlayflooring nails, or 28 mm long staples with 5mm crowns and not less than 1.2 mm shandiameter. Avoid nailing underlayment tojoists supporting the subfloor. Nailing orstapling should begin at one corner of theunderlayment panel and should progressdiagonally across the panel.

Preparation of underlayment prior toapplying floor covering should be done asrecommended by the floor coveringmanufacturer. Such a recommendationshould include sanding uneven surfacesand panel joints to level, filling surface voids

according to the floor coveringmanufacturers procedure and, whenrequired by the manufacturer, a procedurefor filling joint seams. It should also includespecification for a suitable filler.

Field-Glued SubfloorsThis technique provides stiffer, better qualityfloors. With the new adhesives and gluingtechniques available, field-glued combinedsubfloor and underlayment plywood floorssave money while providing premium qualityconstruction. Material and labour costs arereduced with the single floor system, whichcombines the functions of both structural

subflooring and smooth underlayment in asingle layer of plywood. Floor stiffness isalso increased from 20% to 70% (dependingupon the size and spacing of the joists andthicness of plywood) compared toconventional floor construction because theglued plywood floor and joists act togetheras a composite, stiff T-beam unit.

Builders who have adopted this floor systemhave experienced an added benefit -minimum call bacs to repair floor squeas.With field-glued plywood subfloors, the gluefirmly bonds the plywood and joists togetherto help prevent the differential movementbetween the joists and the subfloor whichcauses squeas.

GluesSeveral brands of elastomeric glue suitablefor field use are available from buildingsupply dealers. Most are convenientlypacaged in spouted, ready-to-usecartridges for cauling guns. Some brandsare available in bul for use with portablepneumatic systems. These specialconstruction adhesives are not be confusedwith ordinary drywall glues. Use only gluesspecified for construction purposes and

apply according to manufacturersinstructions.

The Canadian General Standards BoardSpecification CAN/CGSB - 71.26 - M 88establishes minimum performance and testrequirements for elastomeric constructionadhesives for bonding plywood to lumberframing.

Gluing Conditions

Glues are formulated to provide adequatebonds and unseasoned lumber, whichmaes their use practical under normal site

conditions. With several of the adhesivesavailable, gluing can be done in belowfreezing weather provided the temperaturerises above freezing reasonably soon afterthe floor is applied. However, for best resultsthe ambient temperature should be abovefreezing. Gluing should never be done whentemperatures are continually below freezingbecause none of the adhesives currentlyavailable can develop adequate sheastrength under such conditions. The

adhesive should be ept as warm aspossible during cold weather to ensure easeof application.


Hardwood

flooringResilient flooring

CANPLY Select

grade plywoodunderlayment

CANPLY

Sheathing grade

plywood subflooring

Edge blocking

(not necessary

with EASY T&G

plywood)

Resilient flooring

CANPLY Select

grade underlayment

EASY T&G

Sheathing grade

subfloor

Resilient flooring

EASY T&G

Select grade

Cleaned and Sized

single layer subfloor

Underlayment used

to compensate for

difference in thickness between resilient

and wood flooring

Wall to wall

Carpet

Underlayment used

to compensate for

difference in thickness between carpet and

resilient flooring

Combined subfloor

and underlayment

Plywood Subfloor and Underlayment


13/28

Application of EASY T&G Plywood for Regularand Field-Glued Plywood SubfloorsIt is advisable to plan placement of EASYT&G panels to minimize cutting, waste andlabour. Panels should be placed with theface grain at right angles to the supports.End joints, which must occur over supports,should be staggered. When placing thetongued edge of a panel into the groove of apreviously placed panel, care should betaen to ensure that tongues and grooves

are not damaged. Note that each T&Gpanel is stamped THIS SIDE DOWN toensure correct placement. Therecommended application sequence forEASY T&G plywood is as follows:

1. It is important that the first row of panelsbe aligned straight and true. To ensure this,measure a panel width in from the ends ofthe two outside joists and snap a chal linebetween these points. This line will also actas a boundary when applying glue for thefirst row of panels of a field-glued plywoodsubfloor.

2. For a regular subfloor, lay the first row ofEASY T&G panels with the grooved edgealong the chal line and tac in position withfour to six nails per panel. Do not nail within150 mm of the grooved edge in any row untilthe tongues of the following row are inposition.

For a field-glued plywood subfloor, lay a3 mm to 6 mm diameter bead of glue alongthe joists or beams apply glue in aserpentine pattern. Where panel ends willbutt on the joists, lay two beads of glue toensure that each panel end will be glued.

Apply only enough glue to lay one or two

panels at a time (unless the gluemanufacturers instructions permit coveringa larger area in advance of laying thepanels). See Table 11 for glue coverage.Nail panels securely in position taing carenot to nail within 150 mm of the groovededge until the tongues of the following roware in position.3. Place a second row of EASY T&G panelsalong the other side of the chal line with thetongues fitting into the grooves of the panels

in the first row and having the end jointsbetween plywood panels staggered relativeto the first row.Do not attempt to force a tight joint betweenpanel faces as the EASY T&G Floor isdesigned to butt at the tip of the tongueleaving a 1 mm gap on the face andunderside. A 2 mm gap should also be lefbetween panel ends to allow for expansionof the plywood and shrinage in the joistthicness.


Bead Diameter

(mm)

3

5

6

8

10

Litres

per 100 metres

0.7

2.0

2.8

5.0

7.9

Metres

per Litre

142

51

35

20

13

Tbe 11. aroximte Gue Coverge vs Bed Size

Note: 1 U.S. gallon equals 3.78 litres; 1 Imperial gallon equals 4.54 litres

Spliced Floor Joists

EASY T&G Floor Installation

MAINTAIN PROPER GAPS

DO NOT FORCE PANELS

TIGHTLY TOGETHER!

Leave built-in 1 mm

expansion gap

between tongue and

grooved edges.

Leave a 2 mm gap

between panel ends.

3

12

If EASY T&G plywood is used, no

blocking is necessary

Where joists are

continuous over bearing

points, they may be

end-butted, not lapped, to

provide continuous nailing Joist

Beam

CANPLY plywood

splice plates

Edge blocking for

square edge

plywood

Lay panels with face grain

across the joist

NOTE: Adding a bead of

elastomeric glue between

joist and panel helps

eliminate squeaks and

nail popping, and

increases floor stiffness

resulting in potentially

longer spans.Fasteners spaced 150 mm (6") around the perimeter of the panel

and 300 mm (12") on intermediate supports. For plywood thicknesses up

to 18.5 mm, Code approved fasteners include 51 mm common or spiral nails,

51 mm staples and 45 mm ring thread nails or screws.

FaceGrainDirection


14/28


4. Sheathe the remaining floor area. For afield-glued subfloor apply glue in advance ofeach panel and nail each panel securely inplace within the glue manufacturersspecified assembly time. For extra stiffness,a bead of glue, either continuous orintermittent, may be squeezed into thegrooves before mating the panels. Ifapplying a regular subfloor, the panels canbe nailed securely to the joists at this stage.If the plywood is being used as combined

subfloor and underlayment as a base forresilient flooring, panel nailing should be leftuntil the finish flooring is to be laid, at whichtime nailing should be completed and thenail heads set.

5. Protect floor from excessive moisture.

Hints to Reduce Nail Popping in FloorsNail popping is the term used to describethe tendency of some nails to rise above theplywood surface after driving. It becomes aproblem in subfloor and underlaymentapplications only if nails are driven intounseasoned lumber joists. As the lumber

shrins, the whole depth of the joist isreduced, including the depth of the nail hole.With the nail hole reduced in depth the nailhead is raised above the surface of theplywood because the nail itself cannotincrease the depth of the hole. This causeshumps or blisters on the surface of resilientflooring. The tendency for nails to pop canbe reduced by:

1. Selecting lumber joists so that memberswith similar crowns will be placed sideby side.

2. Using dry products, such as k.D. lumber

or engineered I-Joists, whenever possible. Ifunseasoned lumber is used do not fastenplywood permanently until the joists haveattained equilibrium moisture content.

3. Using the shortest possible annularlygrooved nails consistent with therecommendations given in Table 10. Drivenails at a slight angle and set all nail headsprior to laying resilient flooring.

Wall SheathingCANPLY EXTERIOR plywood used as wallsheathing stabilizes the building frameworand maes diagonal and corner bracingunnecessary. Damage to finish materials inthe structure due to uneven settling of theframe is minimized when plywood sheathingis used because plywood adds rigidity to thebuilding. This rigidity is especially importantwhen walls are prefabricated on the floorand then tilted into position, or where wallsare to contain large areas of glass. Plywoodsheathing also contributes to the overallthermal performance of the wall because the

large panels mean fewer joints throughwhich air can lea and heat can escape.

Minimum plywood thicnesses for wallsheathing are given in Table 12. Formaximum performance of the plywood,panels should be applied with the face grainperpendicular to the studs. Plywood panelsshould not be applied to form a tie betweenthe bottom plate and the floor joists orheader or sill, since shrinage of the lumbermay cause the plywood sheathing to bucle.

A strip of plywood along the joist header, asshown in the illustration below, will extendsheathing to the required lower limit of the

wall and provide a flush surface for theexterior siding material. A small gap shouldbe left between panels to allow forexpansion.

Siding and PanelingCombined Sheathing and CladdingThis siding system, sometimes called asingle sin finish, is a sound and economicamethod of wall construction in which

plywood is applied directly to the studs toperform the dual role of structural sheathingand finish siding.

Available in a range of patterns and texturesplywood siding panels combine the naturacharacteristics of wood - warmth, beautyand durability - with the superior strengthand stiffness imparted by cross-laminatedconstruction. This form of construction isone of the least expensive ways to enclosespace and is suitable for most types ofbuildings.

Minimum thicness requirements, support

spacing and nailing schedules for plywoodsiding are given in Table 13.

Plywood SidingPlywood can be used in panel form or cutand applied as lap or level siding. Sheathinggrades of plywood mae an economicacladding with a pleasing rustic appearanceThese grades are especially attractive whenthe plywood is stained with a heavy bodiedstain and the joints are covered with battensor moulding. When the plywood is to bepainted, Medium Density Overlaid plywoodshould be used. This type of plywood has asmooth, durable, resin impregnated surface

ideal for a long lasting paint finish. Texturedgrooved, factory-primed and pre-finishedsiding panels are also available. Hot-dippedgalvanized nails should be used withplywood siding to avoid rust streas. It maybe desirable to use colour-matched nails forsome pre-finished panels. If battens areapplied over pre-finished siding, the battensshould be nailed separately so that they canbe removed for refinishing withoutdamaging the siding.

Wood, Metal and Vinyl SidingSiding should be nailed directly to the studsthrough the sheathing. All vertical joints

should occur over studs. Nails should becorrosion-resistant.

Red Cedar Shingles and ShakesPlywood applied perpendicular to the studsprovides a stiff nailing base for shingles andshaes. They should be nailed directly tothe sheathing with hot-dipped galvanizednails driven flush but not so that the headcrushes the wood.

Plywood Wall Sheathing

Open Joint

Joists

Sill plate

FoundationHeader

Top plate

Studs

CANPLY plywood strip

Stagger panels

for maximum

strength

EASY T&G

plywood Subfloor

Leave 2 mm gap

between paneledges. In wet

service conditions,

increase gap to

3 mm


15/28


StuccoIf self-furring metal lathe is used, it may benailed directly over the plywood sheathingafter applying building paper. Nails shouldbe hot-dipped galvanized, have large headsand be driven through the plywood into thestuds. If wire mesh is used, it should beattached with furring nails.

Brick or Masonry VeneerPlywood sheathing should be covered with

asphalt-impregnated paper lapped 100 mmat the edges. Bric or masonry should beset at least 25 mm from face of sheathing.Metal ties may be secured by nailingthrough the sheathing to the studs.

Spacing of

Supports (mm)

300, 400

480, 600

Plywood

Thickness (mm)

6

7.5

Nailing Schedule for Wall Sheathing

Size and Type

51 mm (2 in.) Common

or

45 mm (1 in.)Annular grooved


150 mm around the

perimeter and 300 mm

along intermediatesupports

Tbe 12. Miimum Thickess of Canply EXTERIOR pwood dniig Schedue for W Shethig

(Recommendations suitable for Housing and Small Buildings governed underPart 9 of the National Building Code of Canada)

1. Plwood ma be applied with face grain parallel or perpendicular to supports.

2. A 2 mm gap shall be left between panel edges. Gap shall be increased to3 mm in wet service conditions.

3. If asbestos cement shingles are to be attached to the sheathing onl, plwoodshall be not less than 9.5 mm thick.

4. If vertical lumber siding or stucco lath or reinforcing are to be attached to thesheathing onl, plwood shall be not less than 12.5 mm thick.

5. If verticall applied metal siding or wood shingles and shakes are to beattached to the sheathing onl, plwood shall not be less than 7.5 mm thick.

300

8

6

66

400

8

6

66

480

11

8

66

600

11

8

66

Condition of Use

Without sheathing or over furring:

Face grain parallel to supports

Face perpendicular to supports

With sheathing:

Face grain parallel to supportsFace grain perpendicular to supports

Nailing Schedule for Plywood Siding

(see note 6 for lap or bevel siding)


Minimum Net Effective Plywood

Thickness (mm)

Size and Type

52 mm (2 in.)

corrosion-resistant

common nails

compatible with siding

for plywood thicker

than 7 mm and 38 mm

(1 in.) nails forplywood up to 7 mm

thick

Maximum

Nail Spacing

150 mm on centre

along edges and

300 mm along

intermediate supports

1. Net effective thickness: For brushed, grooved, striated and saw textured plwood, the net effective thickness is the thickness between the bottomof the scores or grooves and the back face of the plwood.

2. The edges of plwood siding shall be treated with a suitable paint or sealer.

3. Plwood applied in panels must have all edges supported. No less than a 2 mm gap shall be provided between the panels. Gap shall beincreased to not less than 3 mm in wet service conditions. Vertical joints in such siding shall be protected with batten strips or caulking when the

plwood joints are not matched. Horizontal joints shall be lapped not less than 25 mm or shall be suitabl flashed.

4. Plwood applied in horizontal lapped strips shall have no less than a 2 mm gap (3 mm in wet service conditions) provided at the butted ends,which shall be caulked. The horizontal joints shall not be lapped an less than 25mm. Wedges shall be inserted under all vertical butt jointsand at all corners when horizontal lapped plwood is applied without sheathing.

5. Building paper is not required with panel-tpe siding provided all joints are caulked and either covered with battens or suitabl factor-detailed toexclude moisture.

6. Nails for lap or bevel siding shall be 51 mm corrosion-resistant and compatible with the siding. Nails shall be spaced 100 mm oc at verticaljoints and one nail per stud along bottom edge of siding.

7. Clearance of no less than 200 mm shall be provided between the finished ground level and plwood siding and no less than 50 mm betweenroof surface and plwood siding.

Tbe 13. Miimum net Effective Thickess of pwood Sidig d niig Schedue


16/28


Typical Wall Construction Details:

Note: Not all construction details are shown in above diagrams. Wall assemblies should be designed according to local building code requirements and conditions.

Joints - no caulking required for factory-

detailed joints or where the joints are

covered with battens or backed with

building paper.

Leave 2 mm gap between panels edges.

In wet service conditions, increase gap

to 3 mm.

No diagonal wallbracing required with

single skin construction

Insulation as required

Batten (nailsthrough batten

should penetrate

stud at least 25 mm

CANPLY plywood panel siding

Uniform Panel - Board and Batten Grooved Panel - Vertical

Grooved Panel - Horizontal Lap Siding

Joints - no caulking required for factory-

detailed joints or where the joints are

covered with battens or backed with

building paper.

Leave 2 mm gap between panels edges.

In wet service conditions, increase gap

to 3 mm.

Joints - no caulking required for factory-detailed vertical joints or

where the joints are covered with battens or backed with building

paper. Leave 2 mm gap between panels edges.

In wet service conditions, increase gap to 3 mm.

Battens to

conceal butt

joints at panel ends

Lap or

lash

horizontal

joints.

No diagonal wall

bracing required with



Blocking at

horizontal joints

No diagonal wallbracing required with



CANPLY plywood panel siding

CANPLY plywood panel

siding installed horizontally, nail as

required for vertical application


Blocking at

horizontal joints

Shingle wedge

under vertical joints

(lap siding only).

Stagger butt joints

over studs

CANPLY plywood lap siding


Building paper


17/28


Plywood Thickness (mm)


Typical Exterior Wall Corner Details

Corner Boards

Flat Panel

Corner Boards

Lap or Bevel

Butted

Butted

Square Corner

Flat Panel

Corner Stop

Butted

Square Corner

Lap or Bevel

Corner

Moulding

Open Joint

Paint

Method of Edge Support

Panel edges supported by

blocking or H-clips

Panel edges supported by

EASY T&G roof edge profile

Panel edges not supported

300

7.5

7.5

7.5

7.5

400

7.5

7.5

9.5

9.5

480

9.5

9.5

11

11

12.5

12.5

610

9.5

9.5

11

11

12.5

12.5

1200

18.5

20.5

NR

NR

Plywood

Designation

DFP

CSP, Aspen or

Poplar

DFP EASY T&G

CSP EASY T&G

DFP,

CSP, Aspen or

Poplar

Tbe 14. Miimum Thickess of Canply EXTERIOR pwood d

niig Schedue for Roof Shethig

Recommendations suitable for designs governed b Part 9 of the National Building Code of Canada and/orwhere the design live load does not exceed 2.4 kPa

Plywood

Thickness (mm)

7.5, 9.5, 11, 12.515.5, 18.5

20.5

Nailing Schedule for Roof Sheathing

Size and Type

51 mm (2 in.) Common or45 mm (1 in.) Annular grooved




150 mm around the perimeterand 300 mm on centre along

intermediate supports except

that when primary supports are

spaced greater than 800 mm on

centre, nails shall be spaced at

150 mm intervals along all

supports.

Notes:

1. EASy T&G panels are available in thicknesses of 11 and 12.5 mm, and are recommended forsuperior performance as roof sheathing. For details, see pages 18 and 19.

2. Recommendations suitable for flat, flat-pitched or pitched roofs. Because of point loads, whichma be imposed during construction, the tabulated thicknesses should not be reduced nor thetabulated spans increased. For thickness of roof sheathing on a flat roof used as a walkingdeck, follow the recommendations for flooring in Table 10.

3. Plwood shall be applied with the face grain perpendicular to supports.

4. Plwood shall be applied so that joints parallel to rafters are staggered and all adjacentedges are separated b no less than a 2mm gap. In wet service conditions, the gap should beincreased for all panels except EASy T&G to no less than 3mm.

5. DFP - Douglas Fir Plwood meeting CSA O121.

6. CSP or Aspen - Canadian Softwood Plwood meeting CSA O151.

7. Poplar Plwood meeting CSA O153.

8. NR - Not recommended.

800

12.5

15.5

12.5

15.5

15.5


18/28

SoffitsPlywood cut to correct size and naileddirectly to roof joists, rafters or outriggerscan act as soffits. Use 6 mm for supports upto 400 mm on centre and 7.5 mm for600 mm spacings. Cut-to-size and ventedsoffits are available from many buildingsupply dealers. It is a good idea to stain orprime the soffit panels before installation.This will save much wor later. MDOprovides a superior paint surface.

The illustrations opposite show two methodsof placing vents in plywood soffits.

Roof SheathingPlywood roof sheathing offers time andmoney saving advantages while contributingto the overall strength and rigidity of thestructure. In some cases it may be possibleto reduce roof construction costs by usingfewer rafters spanned by a thicer than usualsheathing panel. The high-strength, lowweight, skid-resistant dec provided byplywood sheathing is ideal for all type of

roofing materials, from red cedar shinglesand shaes to built-up roofing.

Table 14 gives minimum requirements forthe application of CANPLY EXTERIORplywood roof sheathing. Panels should beapplied with the face grain at right angles tosupports to obtain maximum strength. Asmall gap should be left between panels toallow for expansion.

During construction, the rafter headershould be applied first. The first row ofplywood panels should then be nailed flushwith the outside edge of the header to give a

true roof edge. The fascia board is thenapplied to cover the rafter header and theedge of the plywood sheathing. Thismethod of construction will also help stopleaage into the soffit if water should bacup the eave.

H-clips are an alternative to solid blocing inconjunction with 9.5 mm plywood roofsheathing spanning rafters placed 600 mmapart, subject to the following conditions:

1. One H-clip shall be placed midway in thejoint of abutting sheets between each pair ofrafters or joists. Rafter or joist spacing shallnot exceed 600 mm.

2. H-clips should fit snugly.3. Abutting plywood sheets shall be fittedas closely as clips permit, providing theseparation required by the National BuildingCode is maintained. Occasional misfit ofabutting sheets may be tolerated providingresulting gaps at maximum opening do notexceed 6 mm.


Rafter

Top Plate

Sloped Soffit

Horizontal Soffit

Wall studs

CANPLY plywood

wall sheathing

Rafter

Top plate

Stud

Continuous nailer

Outrigger

CANPLY plywood

wall sheathing

Vented Soffits

CANPLY plywood

roof sheathing

Fascia

CANPLY plywood

roof sheathing

CANPLY

plywood soffit

Screen vent runs

length of soffit

Fascia

CANPLY plywood soffit

Intermittent screened

soffit vents

EASY T&G Roof Sheathing

Leave 2 mm gap

between panel edges.

In wet service conditions,

increase gap to 3 mm

Roof rafter

Top plateFascia

Rafter header

See Table 14 for

nail spacing

No H-Clips required with EASY T&G

For maximum strength, place

plywood panels across rafters

and stagger joints

FaceGra

in

Direction


19/28

An alternative to sheathing with regularCANPLY plywood is to use EASY T&Gpanels. These panels are manufacturedspecially for roof sheathing and have a new,patented edge profile that results in astiffer

roof and eliminates differential deflection aswell as the need for H-clips. Table 14 givesthicness and nailing recommendations.

Install EASY T&G with tongued edge up (i.e.,pointing toward the top of the roof). An

exception may be made where triangularcut-offs are made, such as when sheathinghipped roofs. When square edge plywoodis used on hipped roofs, the triangular cut-offs are flipped over and used on the otherend of the same row. This is not possiblewith EASY T&G when all panels are installedwith tongued edge up. Instead, install oneside of the roof with the tongued edge upand the other side with the tongued edgedown (i.e., pointing toward the eaves). Thetriangular cut-offs from one side of the roofcan then be used on the other side with noloss of footage.

Panels should be installed with the grainacross supports and applied so that jointsparallel to rafters are staggered. A 2 mmgap between the ends of adjacent panels isrequired. Correct spacing between the longedges of adjacent panels is inherent in thedesign of the edge profile.

Finish Material over Plywood Roof SheathingMany types of roofing materials have provensatisfactory under various service conditionswhen applied over plywood roof sheathing.The most common materials used onsloping roofs are Western Red Cedar

shingles and shaes, asphalt shingles andtiles. For flat or flat-pitched roofs, built-uproofing is generally used. Rolled roofing issuitable for temporary use but is notrecommended for permanent installationover plywood roof sheathing.

When a plywood flat roof dec is to carrypedestrian traffic, it must be considered as afloor or waling dec and the plywoodthicness selected accordingly. Surfacemembranes conventionally used as roofcoatings are rarely suitable for pedestriantraffic and should not be used on walingdecs. However, special coatings which areboth waterproof and abrasion-resistant havebeen developed in recent years and theiruse on plywood waling decs isrecommended.

PERMANENT WOOD FOUNDATIONSPermanent Wood Foundations (PWFs) are acomplete wood-frame foundation system forlow-rise residential, school, industrial,commercial and other types of buildings.Built with preservative treated wood, they arean extension of the familiar wood-framesystem with the frame walls carried below

ground to serve as the foundation.

The first documented uses of woodfoundations of this type were in the Mar IIIand IV experimental homes built in 1961 and1963 at Canadian Forces base, Roccliffe(Ottawa) by the National House Builders

Association (now the Canadian HomeBuilders Association), in cooperation withCanada Mortgage and Housing corporation,the Institute for Research in Construction

and Forinte Canada. The foundation wallsfor both homes were built of preservativetreated lumber framing and plywoodsheathing.

Forinte Canada scientists have inspectedthose wood foundations regularly sinceconstruction and report that treated woodfoundations can be expected to perform aswell as similarly treated wood in groundcontact in other situations. Goodperformance of treated wood in groundcontact has been well established. Many ofthe major structures of the world aresupported on preservative-treated wood

piles, another form of wood foundation.

In the Permanent Wood foundations systemall wood exposed to decay hazard ispressure treated with preservatives. Thepreservatives permanently impregnate thewood cells to penetration and concentrationlevels that mae the wood resistant to attacby decay organisms and termites. Thetreated wood is then dried, resulting in anodourless product with a colourcharacteristic of the preservative used.

Wood foundations lend themselves to plantfabrication or to on-site construction. If the

foundation wall panels are fabricated in theplant, they can be assembled on jig tablesused to frame the upper walls. This speedsup erection at the site, and usually results incost savings and improved quality control.The plywood-sheathed wood frameprovides automatic dimensional controlsbecause plywood panels are square and aremanufactured to precise dimensions.Construction can tae place in most weatherconditions, and can be completed fasterthan with traditional foundations, resulting inreduced construction and lower labourcosts.

The PWF system has many advantages overconventional foundations such as morecomfortable living areas, speedier erectionand reduced energy costs.

Wood frame foundation walls are readilyinsulated to the same high standards as therest of the house, resulting in warm, low-costliving space. They can be finished on theinterior and on the exposed exterior withconventional coverings and finishes.

Construction details, including plywoodsheathing thicness recommendations, for

the PWF system are fully detailed in theCanadian Wood Council publicationPermanent Wood Foundations, and in CSAStandard S406 Construction of PreservedWood Foundations.

CONCRETE FORMSCANPLY EXTERIOR plywood is suitable for alconcrete forming applications. Load/span tablesfor various thicnesses of CANPLY EXTERIOR

Douglas Fir plywood, together with other designdata, are given in the CertiWood publicationConcrete Formwork.

The Advantages of Plywood for ConcreteFormingThe selection of formwor materials shouldbe based on maximum overall operatingeconomy consistent with safety and thequality of finish required. Many contractorshave found that, for the reasons notedopposite, CANPLY EXTERIOR plywoodsatisfies the requirements of economysafety and quality for the majority of concrete

formwor applications.

HandlingIt is generally acnowledged that thegreatest damage to forms occurs during thevarious handling operations. Thoroughplanning of the whole forming operation wileep handling to a minimum. In the interestsof speed and efficiency, mechanicahandling devices should be used wheneverpossible.

To slow the drying rate and minimize facechecing, panels should be stored on a flat

dry surface and staced face to facePanels should be protected against sun andrain but free air circulation must be provided

Release Agents for Plywood ConcreteFormsThe application of a release agent to theform face facilitates stripping the formworand prevents scaling of the concrete surfacewhen the forms are removed.

Many proprietary brands of release agentsare available in North America. Thesebrands vary in composition to suite variousapplications but may for general purposesbe divided into three broad categorieslacquers and paints, oils and greases, andemulsions. It is recommended thatcontractors use only proprietary brands ofrelease agents applied according to themanufacturers instructions.

StrippingTo minimize damage during form removalstripping procedures should be studiedduring form planning with reference tosurface contours and special conditions



20/28

While forms must be left in place a sufficienttime to permit proper curing and protectionof the fresh concrete, it is generally desirableto remove forms as soon as theserequirements have been met.

CANPLY EXTERIOR plywood is a ruggedmaterial, but lie other types of panel forms,plywood can be damaged by prying withcrowbars or by dropping panels on theiredges from a height. If a good release agent

has been properly applied to the plywood,stripping should present no difficulty.

If it is necessary to use force, wooden wedgesshould be used rather than metal pries.

CleaningProper supervision of forming operations onthe job site should extend to the cleaningand repair of forms. Plywood forms, incommon with all other types, should becleaned immediately after stripping.Concrete particles may be removed byusing a wide blunt blade, straw broom or

burlap. Many contractors use a power-driven nylon brush. There are also severalproprietary solutions available for softeningconcrete adhering to the plywood.

Projecting nails should be withdrawn toprevent scarring of panels when stacing.Panels should be staced flat, preferably outof the sun to reduce face checing.

RepairingIt is recommended that plywood forms beinspected after each use and repairs suchas patching or renailing carried out as

required.

Plywood forms should be clean and drybefore repairs are carried out. Where thegrade of plywood and the type of form aresuitable, the plywood may be reversed.Small splits and depressions can be filledwith a suitable patching compound sandedflush. Unwanted holes through the plywoodmay be patched by:

1. Driving a wooden plug in tightly andsanding flush.

2. Bacing up the hole with scrap wood,filling with patching compound andsanding flush.

3. Driving a metal patching disc into theplywood face.

Experience has shown that even if aplywood form is damaged beyondeconomical repairs, the plywood itself canbe salvaged and usefully re-employed innumerous fields, for example as stiffeninggussets on new formwor, as roughfoundation formwor, and in those areaswhere formwor is difficult to remove andmust be left in place.

Hardware for PlywoodConcrete FormsContractors should obtain their hardwareonly from recognized suppliers who canfurnish proof of the strength of theiraccessories by laboratory or field tests.

Although many different types of formhardware have been developed, all standardtypes are suitable for use with plywood. Ofparticular interest are various inds of high

tensile steel ties or bolts which have beenspecifically designed for plywood.

Snap-ties made from high tensile wire arepopular as an inexpensive method of formsupport. These ties are designed to preventthe forms from separating under pressure.Stripping the forms should be done onlyafter concrete has set. After the forms havebeen removed, a tie breaer is applied to the

exposed end of the snap-tie and bent atright angles as close to the wall surface aspossible. The unit is then turned with aclocwise circular motion until the snap-tiebreas at brea-off point.

For most commercial concrete finishes a rodor bar tie with integral spreaders iscustomary. Such ties generally have a notchor similar reduction in section which allowsthe tie to be broen bac a set distance from

the wall surface.

Detailing for PlywoodFormwor costs can be substantiallyreduced if certain basic details ofdimensioning are borne in mind by buildingplanners. Beams and columns preferablyshould have the same outside dimensionsfrom foundation to roof, allowing beam and


Strength

Impact Resistance

Split Proof

Stability

Less Handling

Reusability

Fewer Joints

Insulation

Salvage Value

Easy to Bend

Smooth Face

Simplicity of Repair

Less Storage Space

T&G Edges Available

Ease of Fabrication

Cross-lamination of veneers tends to equalize strength of panel

with and across face grain, permitting the panel to act as a platewhen suitably supported.

Cross-lamination results in high resistance to impact.

Nails can be driven close to panel edge without causing splitting.

Construction of plywood creates a panel which is shrin resistant.

Large panel size reduces number of pieces required. Reduceson-site labour.

The number of re-uses is related to care in handling and strip-ping, and reduction of panel cutting my modular detailing. Five to20 uses are common for quality finish industrial wor. Between50 and 100 uses can be expected for residential foundations.

With fewer joints than boards and other materials, plywood formsare tighter. There is less leaage.

Plywood helps protect concrete from rapid temperature changesand assists in retention of concrete heat in freezing weather.

Even after many re-uses, plywood may be put to wor incountless other applications such as subflooring, ramps,protective barriers and temporary structures.

Plywood can be bent dry to radii determined by thicness ofplywood, direction of bend and the bending procedure itself.Soaing or steaming permits bending to shorter radii. (Table 5)

Large, flat plywood panels provide a concrete surface of uniformsmoothness. Rubbing down and filling are ept to a minimum.

Complex tools are not needed to patch and repair plywood.

Uniform size of large, flat plywood panels maes them easy tostore - on or off the job.

Tongue and groove plywood panels may be used to constructforms on the site, eliminating the need for blocing at paneledges and providing a smooth, joint free surface.

Plywood is easily sawn, bored, routed, etc., with ordinary wood-woring tool and therefore lends itself to special requirements ofcustom form jobs.

Why Plywood for Formwork?


21/28

column forms to be re-used withoutalteration.

A column should preferably be the samewidth as a beam framing into it. The columnform then becomes a rectangular or squarebox with no cutouts, and the slab forms donot require cutting at the columncorners.

It is highly desirable that column, beams

stairwells and other items be sodimensioned that 1200 mm by 2400 mm or1220 mm by 2440 mm panels of plywoodcan be cut with a minimum of waste.

If column centres are set so that the distancebetween faces of beams is a multiple of thepanel width plus an allowance to facilitatepanel removal, whole panels of plywoodmay be used without cutting for slab forms.

Wall Forms: Site BuiltIt is economical to fabricate as much of theformwor as possible on the ground, maingsections as large as can be conveniently

handled by the lifting equipment ormanpower available. Where small piecesare required for such things as stepdownsand special shapes, plywood can be cut tothe exact size required. Horizontal jointsbetween panels may be baced up byheaders or nailing strips to eliminate leaageand produce a smoother joint. For specialcircumstances where a smooth joint-free orfin-free surface is required, the use of tongueand grove plywood with the joints taped withthin, pressure-sensitive plastic tape shouldbe considered. It should be noted howeverthat special care must be taen to preventdamage to the T&G edges.

Nails to fasten plywood to supports shouldbe as small and as few as practical. Forplywood up to 14 mm thic, nails should be44 mm ( 1 3/4) long. For 17 mm plywoodnails should be 51 mm (2) long.

Wall Forms: Panel SystemsIn forming of large areas, standard sizedprefabricated panels can be used for moststructures. As the ties pass through pre-drilled holes it is essential that the forms bealigned correctly on a level footing. Panelform systems can be divided into two broadclasses - unframed and framed.

Unframed FormsUnframed forms are usually 19 mm plywoodpanels. The number of studs or walers islimited. Forms are aligned by means of toeplate and top waler. Ties are insertedthrough holes cut in the panels. A slip-through bar or rod passed through the endsof ties holds panels together. Forms of thistype are most commonly used for residentialand other foundations below grade, and forconcrete walls above grade where thehighest architectural finish is not required.They are easy and light to handle, requiring

little framing lumber. Fabrication by thecontractor is simple. Another advantage isthat both faces of plywood can be used.

Framed FormsThese forms consist of a plywood face from11 mm to 19 mm with wood or metal frames.

Framed forms assist in the production of thehighest quality wall obtainable and by thenature of their construction withstand

rougher use than unframed forms. This formsystem lends itself to gang forming.

Column FormsThere are several methods of formingsquare and rectangular columns. Wheneverpossible, the size of the column should beselected to permit the use of standard 1220mm by 2440 mm plywood panels.

Slab FormsPlywood is easily adapted to accommodatea variety of support spacings and sectionchanges in slab forming. Concrete may bepoured on panels placed directly over

supporting framewor. In all cases, theformwor must safely support the verticaland horizontal loads placed upon it.

Miscellaneous FormsA wide variety of decorative effects can beachieved by pouring concrete intoprepared moulds constructed of plywood.To achieve these special effects, plywoodcan be bent when dry into mild, simplecurves.

Table 5 gives dry, cold-bend radii for mostcommon thicnesses of plywood.Note thatplywood can be bent more sharply when

the bend is perpendicular to the direction ofthe face grain rather thanacross its width. To obtain sharper curves,the plywood must be soaed or steamed.Saw-erfing the bac of the panel to maeit bend more easily is not recommended forstructural applications such as concreteformwor.

Precautions When Forming in Hot and ColdWeatherHot WeatherIn hot weather, concrete must be eptmoist during the curing period. Plywoodforms will prevent almost all moistureleaage, but exposed surfaces should becovered with wetted tarpaulins or curingmembrane. It is also advisable to spraythe exterior surfaces of the forms withwater.

Cold WeatherLower temperatures cause concrete toharden and gain strength more slowly,hence a longer curing time is required toreach specified strength.

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