Timberwork Case StudiesMSc. Building Conservation

22 February 2013

Paul Price

Woodwrights

Oak frame carpentry and timber conservatio

n

Topics:1.Recognising historic carpentry

2.Repairs: surveys and methods

3.Case histories

An overview of historic carpentry and timber

repair

Historic timberworkPart of our built heritage – in Ireland: especially

roofs.A valuable record of historic craftwork - timber

conversion and scribe carpentry.

Christchurch Cathedral,

Dublin. 17th C. oakwork

Ilustrations from:McCracken, E. (1971) The Irish Woods Since Tudor Times

Holy Trinity Church, Fethard, Co.

TipperaryMedieval oak roof

frame, discovered 2010

See-sawing (swivel or trestle sawn)

Timber Conservation Aims

Conserve the overall aesthetic form of the structural

frame while repairing the structure.Preserve original timber as much as possible.

Timber surfaces, which preserve marks recording the original timber conversion and framing methods.

Dunsoghley Castle, Co. Dublin.

High quality scribe carpentry;Double collar; Arch-braces with locking tenons; Scribe numbers visible.

Timber Conservation ProcessSurvey: historical value, condition, and

structure.Repairs: minimal, unobtrusive, reversible.

Outlook: maintenance check-listNorway - Loft repair.Timber replacement: New timber selected, cleft and hand hewn to match original decayed element.

Recognising historic carpentry

Conversion: logs into timber

Carpentry: scribing, jointing and raising frames

Oak - tough and durable. Baltic pine –

imported.

Two forms of historic timberwork:

Treewrightingaxe-hewn, boxed

heart,often smaller ‘stuff’,

cottage roofs;

Frame carpentryhewn plus rip-sawn,mortice and tenon,

large range of scantlings,

use of grown “bends”,larger, more durable

buildings.

Hewing: Turning logs into timber.Marking and notching

Hewing

Notching

Juggling

Finishing with broadaxe

Hewing: Finishing- A broadaxe was used to give a flat finish

Close up of hewn

surface

Stop mark

Axe nick marks

Note mutual angle of marks

Pit-sawn surface with

framers’ level mark

Scribing: Timber placed over full scale layout so thatjoints can be scribed to allow accurate fit of irregular timbers

Plumb bob

Referenceline

Scribed shoulder

Scribe carpentry workshop

Numbering: Usually Roman - chiselled or

race-knifed

Recognising historic timberwork

Hewn or pit-sawn surfaces

Carpenters layout marks - scribe lines and references

Mortice and tenon joints

Chiselled numbers at joints

Scribed joints - shoulders scribed to match irregularities

Repairs: surveys and

methods

Surveys

Record DrawingsBasic survey - Schematic timber drawings and

photographs.Full Survey: Archeological level recording.

EstimatingAnnotate basic survey schematics with current

condition and possible repairs

Bishops Palace, Salisbury, Wiltshire, EnglandRoof by Francis Price 1726 Our repairs 1998

Cathedral Church, Cashel

Nave roof 1780Large span 46ft

=14mTransition carpentry

Diagnosing a structural problem.

– Is it really a problem?

Cashel Cathedral Church Roof:

• Queen post roof with king strut

• Ceiling load has deformed roof

Joint separation 100mm+

Cashel: Structural schematic

Original

Current

Movement appears locked but should be monitored

Repair Methods

Repair Methods for Historic Timberwork

•Steelwork: straps, flitch plates, cables, brackets, bolts, screws to secure joints and framing.

•Carpentry: replacement timbers, patch and end repairs.

•Resin: consolidation, packing, patch and end repairs.

Beware the “honest” repair

Making repairs look distinctive from original workis often an excuse for unsightly repairs.

METAL REPAIRS:•Often cheapest and best if hidden or subtle- no disassembly needed.•Reversible and easier. Unsightly if visible and poorly designed.•Use galvanised or stainless steel for repairs.

CARPENTRY REPAIRS•Potentially damaging disassembly required for replacement or end repairs.•Requires high quality repair carpentry for good results.•Decide whether to match conversion methods.•Use oak with oak etc.

End repairs•require careful fitting and assembly•use dry timber where possible.•may have to use green -allow for shrinkage and later tightening

New tenon repair - only possible if frame elements disassembled

Multiple scarf repairs to softwood wall

Rafter notch joint reformed in resin

RESIN REPAIRS:•Good for consolidating valuable decayed timber and for packing out steel repairs.•Bad for large end repairs. Can be very ugly.•Always use resin designed specifically for structural timber work.

Exposed to weather for 600 years

Timber durability:Excellent if kept dry.Good if sheltered.Bad if continually damp.

Leaking weathervane - king post decayed

Case Histories

Barn, Co. Wicklow18th Century

An exceptional and unusual barn frame

Barn in WicklowShipping marks on Baltic Pine on hewn surfaces.Race knifed symbols denoting timber baulk quality and quantity.

Unusual framed cantilevered roof overhang

Bridled scarf with sallied abutments in a 10 cm by 6.5 cm timber !!

Dragon tie hip assembly: Note numbering

Purlins scribed over hip bevel

Curved EndNew tie and reassembly numbers

Historic pine: Left side has been sandblasted.Note serious loss of fragile but intact surface.

Winchester Cathedral, South TransceptDendro date 1313Difficult working conditionsLaminated in-situ repairs

Disassembly: can see inside joints•Soulace brace with locking tenon•Axed tenon faces•Drawbored tenon•Centre lines

Southwick Barn. Hampshire, England

Collapsing barn- uprighted, mostly in-situ steel repairs

Gusset bracket and flitch repairs

Wooton Bassett,Wiltshire, England

Decay of 19th century oak repairs due to impermeable black paint

Repaired frame prior to stripping impermeable paint

Frame and replastered panels then limewashed

House at Laxfield, Suffolkworking with Traditional Oak Carpentry Co

Structural frame repairs - support carefully!

Cill plate decay - due to constant wetting, impermable paint, and cement mortar/render.

Exterior new timber conserving interior -Coach screwed together with resin packing

Installing new cill with new and repaired timber

Frame reassembled with new plinth built up.Exterior frame aesthetic conserved.

Decay treatment

Interior timber entirely saved.

Poor quality of framing timber -hedgerow stuff

Charlton Court Barn, West Sussex, England

Major repairs•Roof stone removed, frame realigned, joints reassembled•Very costly - steel building over, detailed repairs throughout. Use for special buildings.

Dendro-dated to 1404

Patch repair: coach screwed and plugged

End repairs:Tabled stop splay scarf

New aisle sway brace

New timbers where missing•Re-make in new timber on pattern of existing.•Better than unsightly exposed steel. •Can make decision to match existing conversion to similar pieces.

Purlin span decreased using in-line steel angles - no plywood

Completed frame repair •Aesthetic conserved •Structure repaired

Topics:•Recognising historic carpentry

•Repair surveys and methods

•Case histories

An overview of historic carpentry and timber

repair

Thank-you

Paul Pricewoodwrights.ie