Framing methods

Platform framing, and why it won

In platform framing each storey is built as a complete platform, and the walls of that storey stand on it. The next floor is built on top of those walls and becomes the platform for the storey above.

It won for reasons that have nothing to do with structural elegance. Every member is short enough for two people to handle. Every floor gives the trades a surface to stand on. The repetitive geometry suits factory-made components, and the design method is codified in standards such as those published by the American Wood Council, which the code references. [1]

Its structural characteristics are well understood and well documented, which is worth as much as any technical property: a method that thousands of local builders already know produces fewer defects than a better method they do not.

Balloon framing, and the reason it stopped

In balloon framing the wall studs run continuously from the foundation to the roof, with the intermediate floors hung off them. It was the dominant method before platform framing and it survives in a great many older houses.

It has one property that matters to anyone owning such a house. A continuous stud cavity from basement to attic is a continuous vertical channel, and in a fire it behaves like a chimney. Modern practice interrupts those cavities with fire blocking, and renovation work in a balloon-framed house is generally expected to add it where the work exposes the cavity.

For new construction the method is essentially gone. It appears here because the housing stock is full of it, and because a reader planning work on an older house should know what the framing behind their drywall does.

Advanced framing is an insulation strategy

Advanced framing is a set of adjustments to platform framing that removes wood which is not carrying load: studs at wider spacing, single top plates where the loads line up, framing members aligned so loads pass directly through, corners and wall intersections detailed with fewer studs, and headers sized for the load rather than by habit.

The point is not to save lumber, though it does. It is that every piece of wood spanning the wall is a thermal bridge, conducting heat past the insulation beside it. A framed wall is a composite of insulation and conduction, and the fraction of the wall area that is wood determines how the assembly actually performs. Removing unnecessary wood raises the real performance of the wall without changing a single specification on the insulation.

The trade-off is that it demands more attention from the framing crew, and a crew that has always framed one way will produce a hybrid unless the drawings are explicit. That reasoning connects directly to the envelope series, where the difference between material R-value and assembly performance is the whole subject.

Light gauge steel and mass timber

Cold-formed steel framing is dimensionally stable, does not burn, is not eaten by anything, and is a superb conductor of heat. That last property is the problem. A steel stud short-circuits the insulation around it far more effectively than a wooden one, so a steel-framed wall requires continuous exterior insulation to perform at all, and the detail is unforgiving.

Mass timber is a different proposition entirely: large engineered panels and beams, cross-laminated timber and glued laminated members, structural in their own right and typically left exposed. It is genuinely transformative at scale, which is where it is being used, in mid-rise and non-residential buildings where it competes with concrete and steel.

In a single-family house it usually does not compete with anything. The spans are short, the loads are small, and light framing is already cheap and well understood. Mass timber in a house is an architectural decision, made for the appearance of the exposed structure and for the speed of erection, and it is a legitimate one provided nobody is claiming it on cost.

How to choose, in practice

For almost every detached house in North America the answer is platform framing, and the real decision is how well it is detailed rather than whether to replace it.

The questions that change an outcome are narrower and they belong in the drawings rather than in a method debate. What is the stud spacing and is it justified by the load. How are the corners and intersections framed. Are the headers sized or assumed. Is there continuous exterior insulation and how thick. Each of those is answerable, each affects the finished building, and none requires adopting a different framing method to get right.

The wider argument, that the envelope is one system rather than a set of specifications, runs through the contents sheet under envelope.

One more question is worth asking early, because it is cheap then and impossible later: where are the services going. Plumbing stacks, duct runs and the routes for wiring all pass through the framing, and a framing layout that has not considered them produces a house where somebody solves the problem on site by cutting a member. Coordinated drawings prevent that. Uncoordinated drawings transfer the problem to whoever is holding the saw, which is the worst place for a structural decision to be made.