Platform 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 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 consistent 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. 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.

The framed structure sits atop a concrete (most common) or treated wood foundation.

From the foundation, a framer will bolt or otherwise connect a sole or sill plate. Then, depending on the design of the structure, a framer may install a floor, short “pony walls”, or full height walls.

The floor, or the platform of the name, is made up of joists (usually 2×8, 2×10 or 2×12, depending on the span) that sit on walls and, usually, a beam at the center of the house. The joists are spaced at (12″, 16″, and 24″ on center) and covered with a plywood subfloor. In the past, 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. 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”.

The top floor’s walls receive the roof. A framed roof is an assembly of prefabricated trusses (most common) or hand cut rafters. The roof members are covered with sheathing or strapping in advance of the finish roofing material.

See also

• Balloon framing
• Light-frame construction

Reference

• Canada Mortgage and Housing Corporation (1998). Canadian Wood-Frame House Construction. ISBN 0660172941

Building | Construction | Building engineering | Structural system | Woodworking