House Framing & Structure

The "skeleton" of a house is referred to as the frame. Although some new homes utilize steel framing, most houses still utilize wood for the beams, floor joists, walls studs, roof rafters and other structural components.

To ensure the structure’s strength, all components are sized and built in accord with building codes and are based on common load engineering principles.

Wall framing in house construction includes the vertical and horizontal members of exterior walls and interior partitions. These members referred to as studs, wall plates and lintels, serve as a nailing base for all covering material and support the upper floors, ceiling and roof.

House Framing

There are two methods of framing a house. Balloon framing was common until the late 1940s, but since that time, platform framing has become the predominant form of house construction.

Platform, or stick framing, is a light-frame construction system and the most common method of constructing the frame for houses and small apartment buildings as well as some small commercial buildings in Canada and the United States.

The framed structure sits on a concrete slab or perimeter (most common) or treated wood foundation. A Sill-Plate is anchored, usually with ‘J’ bolts to the foundation wall. Generally these plates must be pressure treated to keep from rotting.

The bottom of the sill-plate is raised a minimum 6 inches above the finished grade by the foundation. This prevents the sill-plate from rotting as well as providing a termite barrier.

The floors, walls and roof of a framed structure are created by assembling (using nails) consistently sized framing elements of dimensional lumber (2×4, 2×6, etc.) at regular spacings (12″, 16″, and 24″ on center), forming stud-bays (wall) or joist-bays (floor). The floors, walls and roof are typically made torsionally stable with the installation of a plywood or composite wood “skin” referred to as sheathing.

Sheathing has very specific nailing requirements (such as size and spacing); these measures allow a known amount of shear force to be resisted by the element. Spacing the framing members properly allows them to align with the edges of standard sheathing. In the past, tongue and groove planks installed diagonally were used as sheathing. Occasionally, wooden or galvanized steel braces are used instead of sheathing. There are also engineered wood panels made for shear and bracing.

The floor, or the platform of the name, is made up of joists (usually 2×6, 2×8, 2×10 or 2×12, depending on the span) that sit on supporting walls, beams or girders. The floor joists are spaced at (12″, 16″, and 24″ on center) and covered with a plywood subfloor. In the past, 1x planks set at 45-degrees to the joists were used for the subfloor.

Where the design calls for a framed floor, the resulting platform is where the framer will construct and stand that floor’s walls (interior and exterior load bearing walls and space-dividing, non-load bearing “partitions”). Additional framed floors and their walls may then be erected to a general maximum of four in wood framed construction. There will be no framed floor in the case of a single-level structure with a concrete floor known as a “slab on grade”.

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

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. day-trips . The roof members are covered with sheathing or strapping to form the roof deck for the finish roofing material.

Floor joists can be engineered lumber (trussed, i-beam, etc.), conserving resources with increased rigidity and value. They allow access for runs of plumbing, HVAC, etc. and some forms are pre-manufactured.

Platform framing often forms wall sections horizontally on the subfloor prior to erection. The top and bottom plates are end-nailed to each stud with two nails at least 3 1/4 in. (82 mm) in length. Studs are doubled at openings, the jack stud being cut to receive the lintels that are placed and end-nailed through the outer studs.

Wall sheathing is usually applied to the framing prior to erection, thus eliminating the need to scaffold. Some types of sheathing, such as asphalt-impregnated fibreboard, plywood, oriented strand board and waferboard, will provide adequate bracing to resist lateral loads and keep the wall square.

Others, such as rigid glass-fibre, asphalt-coated fibreboard, polystyrene or polyurethane board, will not. In this latter case, the wall should be reinforced with a diagonal wood or metal bracing let into the studs.

A multiple-stud post made up of at least three studs, or the equivalent, is generally used at exterior corners and intersections to secure a good tie between adjoining walls and to provide nailing support for the interior finish and exterior sheathing. Corners and intersections, however, must be framed with at least two studs.

Nailing support for the edges of the ceiling finish is required at the junction of the wall and ceiling where partitions run parallel to the ceiling joists.

House Structure

You must know which components are crucial to a house’s structure so that you don’t compromise its strength doing remodeling involving cutting framing members.

Any load-bearing wall removed without reinforcing the structure, can cause serious problems and compromise structural integrity. Floors, ceilings and roof members could sag and windows and doors may stick. If seriously compromised, this could even cause portions of the structure to collapse.

Non-bearing interior walls can be either perpendicular or parallel to joists or rafters. They can be identified from under the house usually since they are not supported by the foundation or beams. Since they don’t support loads, non-bearing walls can normally be removed without compromising a structure.

Foundation and footing deliver loads from the house down to solid soil. Footings must be wider than the foundation in order to properly spread the load.

The weight of a home’s roof materials and loads compresses the roof rafters, which pull ceiling joists from each end and places them under tension. The triangle thus created transfers roof loads to the rafter ends so the weight may be supported by the walls.

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