Laying Insulation Under Plywood in an Attic

Dress in the proper clothing and safety gear, including long pants, a long-sleeved shirt, work gloves, a face shield and a dust mask.

Enter the attic, and pick up all of the sheets of plywood flooring. As you remove the plywood sheets, walk and stand on only the boards that run across the attic floor; the boards are the attic floor joists. Don't step on the area between floor joists because you may fall through it to the floor below. Stack the plywood sheets in an out-of-the-way corner.

Measure one of the long floor joists. If other floor joists are shorter or longer, measure them, too. Write down the measurements.

Mark 2-by-3-inch boards at the same length as the attic joist or joists. Cut the 2-by-3 boards to size with a circular saw.

Attach the 2-by-3 boards directly on top of the attic floor joists by using a hammer and nails.

Walk to one side of the attic, and lay a roll of batt insulation in the cavity between two of the floor joists. Place the insulation's end 5 to 6 inches from the eaves. Unroll the insulation until you reach another joist or the other side of the attic, and cut off the excess insulation with a utility knife. Keep the end of the insulation 5 to 6 inches from all eaves.

Repeat the process to install batt insulation between each cavity between floor joists.

Place all of the plywood sheets back into place, ensuring the end of each plywood sheet straddles two underlying attic joists.