Chapter 28

Structural Components of Framed Construction

Introduction• All phases of drafting have their own

terminology– Terms for basic structural components of

residential construction refer to the:• Floor• Wall• Roof components

Floor Construction• Conventional floor framing

– Involves the use of members 2" wide placed one at a time in a repetitive manner

– Mudsill, or base plate rests on masonry foundation and provides a base for all framing

– Girder (i.e., beam) support floor joists– Laminated girders are used in areas a large

open space is desirable (e.g., basements)

Floor Construction (cont’d.)• Conventional floor framing (cont’d.)

– Engineered wood girders and beams are common in residential construction

• Laminated veneer lumber (LVL) offers superior performance and durability

– Steel girders are used where foundation supports must be kept to a minimum

– Posts are used to support the girders• Wooden posts or steel columns

Floor Construction (cont’d.)• Conventional floor framing (cont’d.)

– Floor joists are repetitive structural members used to support the subfloor (i.e., rough floor)

• A cantilever is a joist that extends past its support

– I-joists are a high-strength, lightweight, cost-efficient alternative to sawn lumber

• Form a uniform size• Have no crown• Do not shrink

Floor Construction (cont’d.)• Conventional floor framing (cont’d.)

– Open-web floor trusses are a common alternative to using sawn lumber for floor joists

– Steel joists are used to support the floor• A 6" x 6" x 54 mil L-clip angle is bolted to foundation

to support the track that will support the floor joist

– Floor bracing keeps joists from rolling over on its side (e.g., rim joist or blocking)

– Floor sheathing forms the subfloor

Floor Construction (cont’d.)• Conventional floor framing (cont’d.)

– Floor underlayment provides a smooth impact-resistant surface

– Common engineered stamp markings • Grade designations• Span rating• Bond classifications• Thickness• Group number

Floor Construction (cont’d.)• Post and beam construction

– Mudsill is installed as with platform construction

– Girders are placed supporting floor decking• Post support girders

– Decking material laid over girders forming the subfloor

• Usually finished similarly to conventional decking with a hardboard overlay

Framed Wall Construction• Bearing walls

– Support itself and the roof weight or floors constructed above

– Requires support under at the foundation or lower floor level (e.g., girder or bearing wall)

• Nonbearing walls (i.e., partitions) – Serve no structural purpose– Used to divide rooms

Framed Wall Construction (cont’d.)• Wall construction

– Made of wood or engineered lumber– Sole or bottom plate helps disperse loads from

wall studs to floor system• Hold studs in position

– Studs are vertical framing members • Transfer loads from top of the wall to floor system

Framed Wall Construction (cont’d.)• Wall construction (cont’d.)

– Wall sheathing insulates against weather and provides backing for exterior siding

• When used on exterior walls it provides double-wall construction

• In single-wall construction, wall sheathing is not used, and siding is attached over a vapor barrier

– Structural wall sheathing (e.g., plywood) is used to resist a wall’s twisting or racking

Framed Wall Construction (cont’d.)• Wall construction (cont’d.)

– Let-in braces are an alternative to using engineered materials for shear panels

– Blocking helps provide stiffness• No longer required unless a wall exceeds 10′ high

Framed Wall Construction (cont’d.)• Wall construction (cont’d.)

– Framing members for wall openings

Framed Wall Construction (cont’d.)• Wall construction (cont’d.)

– Modular wall framing• Components are shipped in containers

• Exterior wall protection– Prior to installing siding, the home is covered

with a weather-resistant exterior wall envelope• Water barriers• Moisture and air barriers• Exterior caulking

Framed Wall Construction (cont’d.)• Interior wall protection

– Vapor barrier • Membrane placed on warm side of walls and ceilings

between drywall and insulation

– Interior caulking• Specified to reduce air infiltration

– Interior finish• Gypsum board, green board, or sound-deadening

board

Roof Construction• Common roof terms:

– Eave– Cornice– Eave or bird blocking– Fascia– Ridge

– Sheathing– Finishing roofing– Flashing– Roof pitch

dimensions

Roof Construction (cont’d.)• Conventionally framed roofs

– Involve the use of wood members placed in repetitive fashion

– Stick framing involves the use of members (e.g., ridge board, rafter, and ceiling joists)

Roof Construction (cont’d.)• Truss roof construction

– A truss is used to span large distances without intermediate supports

• Prefabricated or job built

Roof Construction (cont’d.)• Truss roof construction (cont’d.)

– Truss gains its strength from triangles formed throughout it