In the last update, we covered laying down the supports for our raised plywood floor structure. Next step is fitting insulation to the spaces between the joists. We’re using polyiso rigid foam, which is pretty standard stuff that you can find at Home Depot, etc. It comes in 4’x8′ sheets and several different thicknesses; we’re using 1/2″ here to fit under the plywood between our 3/4″ supports.
This is a pretty simple process: measure all the dimensions of the section you want to fill (including any center supports or wall beams that need to be cut out), mark them out on your sheet insulation, and cut with a knife.
I used a small pocketknife with a straight, sharp blade to make initial cuts accurately along the lines, then a putty knife to finish. The long, thin blade on the putty knife makes it easy to quickly finish the cut using the initial, neat slice as a cutting guide.
Next, we fit the pieces into our intended spaces to make sure they fit. Make any necessary trim cuts and set them in place. I’m not being too careful here about leaving gaps because we’re going to fill them in with spray foam later, and they’ll be hidden under the floor.
Voila! Before you know it, you’re done.
In the next update, we’ll finish the floor insulation with spray foam, then begin adding the plywood sheet over the floor supports.