Attic Subfloor Thickness

Attic joists for live loads.

Attic subfloor thickness.

Standard joist spacing for the installation of attic flooring materials is 16 inches on center oc meaning the distance from the center of one joist to the center of the next joist is 16 inches. Take the measurements for your subfloor and measure enough plywood so that you can cover the entire frame. The decision regarding the thickness of plywood to use for the subfloor in the attic has a lot to do with how you intend to use the attic and it also depends on the spacing of the ceiling joists. The difficulty comes from the precise measurement and cutting required and the labor of getting the sheets of underlayment in place.

For the small difference is cost use 3 4 inch sheathing or underlayment. Attic joists that are made from 2x8s may be acceptable for building your attic floor but because every room is variable there are no absolutes. How to build a subfloor in an attic. A subfloor is a stiff wood underlayment secured directly the the flooring joists.

You also need to ensure that the joist spacing is adequate. Simple sheathing cdx or underlayment should work fine. Covering part or all of the ceiling joists in the attic is a cheap way to make use of wasted space. Purchase half inch 1 27 cm thick plywood to act as your flooring.

It provides a stable surface for finished flooring material such as laminate. Installing the subfloor is the easy part. You ll need to make sure that the plywood can fit through your attic door.