Light Gauge Steel Framing

8/16/2019 Light Gauge Steel Framing

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Dr. Mohammed Ghonim

10. LIGHT-GAUGE STEEL FRAMING

COLLEGE OF ARCHITECTURE AND PLANNING

Department of Architecture and Building Sciences

ARCH 436Contem porary Building Construction Met hods

Lecture Objectives

Upon completion of this lecture, the student will be able to:

1. Explain the concept of light-gauge frame construction.

2. Discuss the advantages and disadvantages of light-gauge frame construction.

3. List the types of light-gauge frame construction.

4. Describe the contraction process of light-gauge frame construction.


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Lecture Content

• Introduction.

• Historical Brief.

• Applications of Light-gauge Steel Framing.

• Cold Forming Process.

• Steel Galvanization.

• Advantages & Disadvantages of Light-

gauge Framing.

• Light-gauge Steel Members.

• Light-gauge Steel Joist Floors.

• Light-gauge Steel Stud Walls.

• Light-gauge Steel Rafter Roofs.

• Framing Process.

• Finishes for Light-gauge Steel Framing.

• Electrical & Plumbing Installations.

• Tools Used in Light-gauge Steel

Construction.

Introduction

Light gauge steel construction is the noncombustible equivalent of wood light frame

construction. The external dimensions of the standard sizes of light gauge members

correspond closely to the dimensions of the standard sizes of nominal 2-inch (38-mm)

framing lumber.

These steel members are used in framing as closely spaced studs, joists, and rafters in

much the same way as wood light frame members are used, and a light gauge steel frame

building may be sheathed, insulated, wired, and finished inside and outside in the same

manner as a wood light frame building.


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Historical Background

The use of cold-formed steel members in building construction began in the 1850s in both

the United States and Great Britain. In the 1920s and 1930s, acceptance of cold-formed steel

as a construction material was still limited because there was no adequate design standard

and limited information on material use in building codes. One of the first documented usesof cold-formed steel as a building material is the Virginia Baptist Hospital, constructed

around 1925 in Lynchburg, Virginia. The walls were load bearing masonry, but the floor

system was framed with doubleback-to-back cold-formed steel lipped channels. In the 1940s,

Lustron Homes Company, built and sold almost 2500 steel-framed homes in America, with

the framing, finishes, cabinets and furniture made from cold-formed steel.

Lustron HomesVirginia Baptist Hospital

Applications of Light-gauge Steel Framing

Light-gauge (Cold-formed) steel framing refers specifically to members in light-frame

building construction that are made entirely of steel sheets, formed to various shapes at

ambient temperatures. The most common shape for light-gauge steel is a lipped channel,

although “Z”, “C”, tubular, “hat” and other shapes and variations have been used. The

building elements that are most often framed with cold-formed steel are floors, roofs, and

walls, although other building elements and both structural and decorative assemblies may

be steel framed.

In high-rise commercial and multi-family residential construction, light-gauge frames are

typically used for interior partitions and support of exterior walls and cladding. However, in

many mid-rise and low-rise applications, the entire structural system can be framed with

light-gauge steel members.


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Cold Forming Process

In building construction there are basically two types of structural steel: hot-rolled steel

shapes and cold-formed steel shapes. The hot rolled steel shapes are formed at elevated

temperatures while the cold-formed steel shapes are formed at room temperature. Cold-

formed steel structural members are shapes commonly manufactured from steel plate,

sheet metal or strip material. The manufacturing process involves forming the material by

either press-braking or cold roll forming to achieve the desired shape.

Cold Forming Process

Cold-formed steel (CFS) is the common term for products made by rolling or pressing thin

gauges of sheet steel into goods, cold-formed steel members are created by the working of

steel sheets using stamping, rolling, or presses to deform the sheet into a usable product.

Cold-formed steel products are commonly used in all areas of manufacturing of durable

goods like appliances or automobiles but the phrase cold form steel is most prevalently

used to described construction materials.

Cold-formed steel construction materials differ from other steel construction materials

known as hot-rolled steel. The manufacturing of cold-formed steel products occurs at room

temperature using rolling or pressing.


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Steel Galvanization

Galvanization is the process of applying a protective zinc coating to steel or iron, to

prevent rusting. The most common method is hot-dip galvanization, in which parts are

submerged in a bath of molten zinc.

Although galvanizing will prevent attack of the underlying steel, rusting will be expected,

especially if exposed to the natural acidity of rain. For example, corrugated iron sheetroofing will start to degrade within a few years despite the protective action of the zinc

coating. Marine and salty environments also lower the lifetime of galvanized steel because

the high electrical conductivity of sea water increases the rate of corrosion primarily

through converting the solid zinc to soluble zinc chloride which simply washes away.

The Advantages & Disadvantages of Light-gauge Framing

Advantages Disadvantages

Like wood light framing: flexible, simple to construct,

and accept the same interior and exterior finishes.

Readily conducts heat and requires extra attention to

eliminating thermal bridging effects.

Noncombustible. Members require more frequent bracing.

Lighter weight, so it is an advantage in seismic zones Although it is galvanized, it is subject to corrosion.

Less waste and recyclable. More expensive, specially in the labor part.

Steel is not subject to fungal decay or termite attack. Conducts electricity if not well isolated.


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Light-gauge Steel Members

For studs, joists, and rafters, the steel is formed into C-shaped sections. The webs of

cee members are punched at the factory to provide holes at 2-foot (600-mm) intervals; these

are designed to allow wiring, piping, and bracing to pass through studs and joists without the

necessity of drilling holes on the construction site. For top and bottom wall plates and for

joist headers, channel sections are used.

The strength and stiffnessof a member depend on the shape and depth of the section and the

gauge (thickness) of the steel sheet from which it is made.

A standard range of depths and gauges is available from each manufacturer, but commonly

used metal thicknesses for loadbearing members range from 2.46 mm to 0.84 mm, and are as

thin as 0.45 mm for nonloadbearing members.

Light-gauge Steel Joist Floors

Light-gauge steel joists are

manufactured by cold-forming

sheet or strip steel. The

resulting steel joists are lighter,

more dimensionally stable, and

can span longer distances than

their wood counterparts, but

conduct more heat and require

more energy to process and

manufacture. The cold-formed

steel joists can be easily cut

and assembled with simple

tools into a floor structure that

is lightweight, noncombustible,

and damp proof.


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As in wood light frame construction,

the framing contains cavities for

utilities and thermal insulation and

accepts a wide range of finishes.


The web stiffener is an important piece in

light-gauge steel floors that is inserted

inside the joist and screwed to its vertical

web to help transmit wall loads vertically

through the joist.

Web Stiffener


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Light-gauge Steel Stud Walls

Light-gauge steel studs are manufactured by cold-forming sheet or strip steel. The cold-

formed steel studs can be easily cut and assembled with simple tools into a wall structurethat is lightweight, noncombustible, and damp proof. Metal stud walls may be used as

nonloadbearing partitions or as bearing walls supporting light-gauge steel joists. As in wood

light frame construction, the stud framing contains cavities for utilities and thermal insulation

and accepts awide range of finishes.



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Typical detail of the anchorage of a cold-formed steel bottom track to the foundation.


Tilt-up construction is used for building stud walls

Hold-downs

Detailed view for a CFS stud wall

Horizontal bracing Diagonal bracing


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Light-gauge Steel Rafter Roofs

Because assemblies are prefabricated, roof framing is in the form of trusses. Being lighter than corresponding wood trusses, cold-formed steel trusses can generally be hoisted into

position without special lifting and hoisting equipment.

Additionally, the joints between members of a cold-formed steel truss are more rigid, so that

the trusses are easier to handle and more forgiving during their placement.

Detail at ridge.

Light-gauge Steel Rafter Roofs

Typical eave detail

The depth of light gauge steel roof trusses is

usually based on the desired roof pitch. A typical

depth is one quarter of the width (span) of the

building.


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Framing Process

The sequence of construction for a building that is

framed entirely with light gauge steel members is

essentially the same as for a building framed with

nominal 2-inch wood members.

Framing is usually constructed with the platform

method; the ground floor is framed with steel joists.

Mastic adhesive is applied to the upper edges of the

joists, and wood panel subflooring is laid down and

fastened to the upper flanges of the joists with

screws. Steel studs are laid flat on the subfloor and

joined to make wall frames.

The wall frames are sheathed either with wood panels

or, for noncombustible construction, with gypsum

sheathing panels, which are similar to gypsum

wallboard but with glass mat faces and a water-

resistant core formulation. The wall frames are tilted

up, screwed down to the floor frame, and braced.

The upper-floor platform is framed, then the upper

floor walls. Finally, the ceiling and roof are framed inmuch the same way as in a wood-framed house.

Prefabricated trusses of light gauge steel members

that are screwed or welded together are often used to

frame roofs.

Finishes for Light-gauge Steel Framing

Any exterior or interior finish material that is used in wood light frame construction may be

applied to light gauge steel frame construction.

Whereas finish materials are often fastened to a wood frame with nails, only screws may be

used with a steel frame. Wood trim components are applied with special finish screws,

analogous to finish nails, which have very small heads.


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Electrical & Plumbing Installations

The above pictures show the electric and plumbing installations for CFS buildings and the accessories used.

Tools Used in Light-gauge Steel Construction

Screw Gun Torched Cutter Power Saw

Power Shear Power Riveting toolTin Snips


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Summary

• Light gauge steel construction is the

noncombustible equivalent of wood

light frame construction.

• Light-gauge (Cold-formed) steel framing

refers specifically to members in light-

frame building construction that are

made entirely of steel sheets, formed to

various shapes at ambient

temperatures.

• CFS framing resembles wood light

framing in many aspects as; it is

flexible, simple to construct, and accept

the same interior and exterior finishes.

• CFS framing is more advantageous than

wood light framing in many aspects as;

it is noncombustible, Lighter in weight, less inwaste, recyclable, and it is not subject to

fungal decay or termite attack.

• The sequence of construction for a buildingthat is framed entirely with light gauge steel

members is essentially the same as for a

building framed with nominal 2-inch wood

members.

References

• Allen, Edward & Lano, Joseph (2009) Fundamentals of Building Construction: Materials andMethods, John Wiley & Sons.

• Ching, Francis (2008) Building Construction Illustrated, John Wiley & Sons.

• Mehta, Madan et. al. (2013) “Building Construction”, Pearson, USA.

• http://en.wikipedia.org

• http://youtube.com


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Lecture Activity

Each student is required to prepare a brief but informative internet-based research about one of the topics

related to this lecture (Light-gauge Steel Framing) Timber Construction); i.e., new developments, successive

and local case studies or important details. The research should be presented in only one A4 sheet.

Light Gauge Steel Framing

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