It s a good idea to rip long thinner strips of plywood that will fit through the attic door.
Attic flooring thickness.
At least 7 feet in any direction.
Floor space dimensions.
If you plan to finish the floor in the attic and turn the room into a living space however you should always use 3 4 inch.
Cdx plywood should be a minimum of 7 16 inch thick.
Note from this chart that the ideal r value differs for each part of your home.
Joist dimensions are only part of the equation.
You also need to ensure that the joist spacing is adequate.
You don t want lots of different floor heights or walking in the attic will be difficult.
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.
To prevent homeowners from building strangely configured and potentially dangerous spaces.
For example if you have a type of insulation that has an r value of r 5 per inch of thickness you will need a depth of 6 inches of this insulation installed your attic to reach r 30 if you live in zones 2 or 3.
The thicknesses are as follows.
No matter what the spacing is on your ceiling joists 3 4 inch plywood should be used if you plan on walking on it.
Purchase half inch 1 27 cm thick plywood to act as your flooring.
If you ever need to cover them with finished flooring you can always nail down another subflooring before installing tile or hardwood.
Attic joists for live loads.
19 32 and 5 8 inch thick.
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Take the measurements for your subfloor and measure enough plywood so that you can cover the entire frame.
If you plan on placing the plywood around the perimeter of the opening or door and using it only to store light boxes or materials 1 2 inch thick plywood should suffice.
You ll need to make sure that the plywood can fit through your attic door.
Use old boards that are close to the same thickness in a given section of the attic however.
Attic flooring panels are easy to install with their interlocking edges.
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.
These lightweight easy to manage panels can be installed by even the most inexperienced homeowner in about 15 minutes.
As an example a floor space that totals 70 sq.
A single 4 pack covers approximately 10 sq.
In one scenario this would translate to a bare minimum of 7 x 10.