Putting Plywood Over Attic Insulation

Always cover the tops of the ceiling joists to make sure the insulation is deep enough to reach your target r value and to prevent thermal bridging the heat loss that occurs through the wood framing.

Putting plywood over attic insulation.

Place the sheets of plywood so that the edges of each board ends at the center of the floor joists with a 1 8 inch gap between adjacent boards on the same joist to allow for wood expansion. I feel like i have to treat this assembly like an unvented flat roof or cathedral ceiling and do a flash and blow or flash and batt method instead. So you can put 8 inches of insulation down then put the plywood over that. Seal any gaps around the perimeter of the attic with caulk and install baffles on the roof decking over the soffit vents.

In my mind i am putting the dew point inside the floor assembly with this approach and risking collecting moisture on the underside of my plywood attic floor. Baffles prevent insulation from blocking the vents. We bought a townhouse last month which has a 400 sq. Put on work gloves safety glasses and a dust mask before entering the attic.

If your attic joists won t bear the weight necessary to finish out a living space but the engineer cleared them to support floor decking for light storage you can install inch plywood or. Now in your particular part of the country you re going to want a lot more insulation than that. Work from the perimeter of the attic toward the door or hatch so that you don t trample all over the insulation you just put in. To solve this problem add another course of 2 x 4 or even 2 x 6 stringers either on top of the existing joists or attached to the sides of the truss.

So what you might want to do is sort of map out an area in the center of the attic where you have your storage and then the rest of the area you could put more insulation. Wear long sleeves and pants since fiberglass insulation irritates the skin if it comes into contact with it. However if you keep the storage weight to a minimum you may be able to build a storage platform above the insulation by attaching supporting beams to the sides of the trusses. If you try to put the plywood flooring directly on the joists it will crush the insulation down and you ll end up with the equivalent of r 15 regardless of what you started out with.

Even easier you can also use a prefabricated attic floor kit designed specifically to raise the attic floor above the insulation. Attic with loose fill insulation between the joists filled up to about 1 2 inches over the top of the beams.