Putting Plywood Over Attic Insulation

We bought a townhouse last month which has a 400 sq.

Putting plywood over attic insulation.

Attic with loose fill insulation between the joists filled up to about 1 2 inches over the top of the beams. Lay sheets of the plywood onto the floor spanning the joists with a 1 2 inch space between the walls of the attic and the edges of the plywood. 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. Baffles prevent insulation from blocking the vents.

Now in your particular part of the country you re going to want a lot more insulation than that. 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. 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. Put on work gloves safety glasses and a dust mask before entering the attic.

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. 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. We were considering putting some plywood down over the joists for some added storage space but i ve read that you shouldn t do that with loose fill insulation because. Seal any gaps around the perimeter of the attic with caulk and install baffles on the roof decking over the soffit vents.

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. 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. 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. Wear long sleeves and pants since fiberglass insulation irritates the skin if it comes into contact with it.

So you can put 8 inches of insulation down then put the plywood over that. 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.