Subfloor framing

A timber floor's joists, bearers and piles laid out on its plan, their sizes and each pile's footing, and the piles that brace it, to NZS 3604.

  • NZS 3604:2011
Tools

How each step is worked out: subfloor framing, what NZS 3604 covers.

Joists, bearers and piles

NZS 3604:2011 5.5, 6, 7.1

Draw the floor's outline, or use the building's from the bracing plan, and choose the floor load and spacings; the floor is laid out on it. Click a pile to make it brace, drag a row of bearers to move it.

The floor

Floor load

Flooring

Joists at, mm

Floor above the ground

Bearers and piles

Bearers run

Bearer spacing

Piles along a bearer at, m

Piles inside carry

For the subfloor's bracing

Subfloor cladding

Walls and roof

Their heights, form and pitch are on the Building tab

Works best with a plan drawn to scale and printed on A3 or A4, with its grid lines, no furniture, and the walls, doors and windows drawn clearly.

Click a floor to choose it, a pile tool above to change its piles. Drag a row of bearers to move it.

Floor 1
Ordinary pile
Carries the floor down to its footing. It does no bracing. Drawn to scale, 125 mm square.
Anchor pile
Drawn solid. Set deep and bolted to the bearer and joists, it braces the floor both ways on its own.
Braced pair
Two piles with a diagonal timber brace between them, both on braced footings. It braces the floor the way the brace runs.
Foundation wall
Reinforced concrete or reinforced masonry, along a side of the floor. It braces the floor along its length, rated by its length against its height.
Footing
The concrete footing under each pile, dashed, at the round size this pile needs.

Between the spans a table prints, the next one up is read, never interpolated; past its last, the floor wants specific design.

A pile's spans are the average of those either side of it; a pile at the end of a row or the edge of the floor takes its one span whole.

Piles under the outside walls carry the storeys above; those inside carry the floor only, unless loadbearing walls stand over them.

Joists are sized for single spans; a joist continuous over two or more may span a tenth further, which is not counted here.

This tool reads NZS 3604:2011 and sets out what it says for the floor drawn. It is not a substitute for reading it, for the judgement of a suitably qualified person, or for the decision of the building consent authority.

standards.govt.nz