Framing

Wood Framing Basic Info

Home Wood Frame Construction

Since the early 1920's, almost all homes have been built using wood frame construction. The reasons for this are both economic and structural. Wood studs, typically 2” X 4” spruce or fir boards, are inexpensive and strong. The framing must be accurate. If the framing is poor quality, the drywall won't be flat, the floors will squeak, and doors will not close correctly. The hubbub at a home construction site may be confusing to the innocent bystander but understanding wood frame construction is actually very simple.

 The Anatomy of an Interior Wall

Understanding the anatomy of an interior wall isn't difficult; think of it as the home's skeleton. Interior wood stud walls can be built in any direction but are usually built at right angles to each other. Interior walls (and exterior walls for that matter) have three basic components: the top plate, the bottom plate and the studs that connect them. The spacing between the studs depends on the local building codes. The most common spacing is 16” or 24” on center. This makes drywall hanging easy and minimizes the amount of drywall finishing, drywall and insulation wastage. Once again, pennies count in this game. For the most part, 2x4 Studs accommodate R12 insulation and 2x6 studs accommodate R20 insulation and plumbing stacks

Spanning Wall Breaks with Window and Door Headers

There are three places where wall studs are discontinuous. In the case of windows, the top and bottom plates are still there but with doorways and case openings the bottom plate is missing. So, how can the wall retain its strength, especially if the wall framing is load bearing? Enter the header. The window or door header spans the distance between the existing studs and the area between the header and the top plate is filled with short studs, called cripples. The same 16” or 24” spacing is maintained. Headers are nailed between the studs' long side vertical and short side horizontal. This takes advantage of the strength of the grain in the lumber.
The header consists of two boards back to back (laminated) with a ½” filler. For a short span 2” X 4”s are used but longer spans demand wider boards.
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Load Bearing Walls vs Non-Load Bearing Walls

These are two types of interior wall framing. Again, the terms are self explanatory. As a general rule, load bearing walls run perpendicular to the roof trusses (rafters) or ceiling joists. They bear the weight of the roof and structure above them.
Non-load bearing walls are any walls that are not engineered to perform any weight bearing function.
When any home remodeling or repair is being planned; careful consideration should be given to load bearing walls. Any moving or removing of load bearing walls must be done in such a way that the home's structural integrity is not compromised.

Stairs
Stairs between floors are framed by installing stepped “stringers” and then placing the horizontal “treads” and vertical “risers”.

Roofs
A framed roof is an assembly of rafters and wall-ties supported by the top story’s walls. Prefabricated and site-built trussed rafters are also used along with the more common stick framing method. “Trusses” are engineered to redistribute tension away from wall-tie members and the ceiling members. The roof members are covered with sheathing or strapping to form the roof deck for the finish roofing material. The city inspector will usually request the truss engineering calculation during the framing inspection.
Stick built roofs allow for a little more design flexibility and better use of attic space. Carpenters cut and assemble boards on-site. Material for a stick-built roof is cheaper than trusses; however labor costs a make stick-built roof more expensive

Joists
In traditional platform framing a platform or floor is built on the foundation. The structure is bolted to the foundation with anchor bolts and hold down straps. Walls are placed on top of the floor joists, followed by the roof trusses Traditionally; the floor joists are made of 2x8 - 2x12 boards. However, today the best choice for floor trusses are composite "I" beam joists. They allow access for runs of plumbing, HVAC, etc. and some forms are pre-manufacturedThey are environmentally friendly using up to 60 percent less wood to make than a solid wood joist and are straighter, stronger and lighter than traditional floor joists.
The subfloor made of 3/4 inch OSB or plywood is attached to the joists with nails and glue to prevent squeaks later on. Using screws instead of nails is highly recommended

The Roof

The roof is formed with pre-manufactured trusses or stick-built on-site. Trusses are built off-site. They are delivered to the site and hoisted onto the walls using a crane. Trusses are strong, install quickly, and can be built to almost any roof design. They are engineered to sustain a live load, dead load, wind resistance and snow load (see construction dictionary).
That's wood frame construction in a nutshell. Once exterior sheathing and interior drywall are installed, the home's strength is greatly increased.