46: Subfloor Going In

The subfloor is finally going in. I can actually walk around on it. I didn’t ever think I would get to this point, but I’m here.

I had to temporarily remove the metal siding from the workshop to get the first floor joist in tight. I expected it to be a major hassle, but it came off and went back on pretty smooth.

I decided to put down the floor joists and subfloor together, rather than doing all the joists, then starting on the subfloor; so that I could adjust the location of joists a little if needed (yes, it has been needed). If you just measure out your joists and put them religiously on 24” centers (or whatever spacing you choose), by the time you get the third sheet down (ie 24 foot of length) you will basically be off the joist for your 4th sheet. So, every eight feet I add in 1/8” for better centering.

Where the ceramic tile goes (foyer, kitchen, utility room, bathrooms) I have used 16” spacing for the floor joists. Over the 16” spacing the floor does feel a little more solid than over the 24”, but there is no bounce or squeaks on either spacing. I’ve jumped up and down on it a lot, testing it for bounce.

I’m using ¾ tongue and groove OSB for the subfloor. It is glued down with subfloor adhesive and screwed down every 12” (about 25 screws per 4x8 piece). All the material I read said run the 8’ edge perpendicular to the floor joists and stagger or overlap each row by four feet as you go. Sometimes getting the tongue on one piece to fit inside the groove on the adjacent sheet has been trying. But, the auspicious use of a 4 lb sledge and a block of wood (to protect the edge) has coaxed things into alignment. When that didn’t work, I found setting a couple of concrete blocks on the new piece has held down the tongue edge enough to allow it to slip into the groove.

As I’m doing this by myself, here’s what I’ve found works for me. First, lay out the new subfloor piece to see how well the tongue and groove are going to line up. Next, set your concrete blocks where you need to push the tongue down a little. Then, after everything is aligned, pick up the other end and stick a 12” wood block in to hold the edge up. Then, squirt your subfloor adhesive in on top of the joists. Then take out the wood block and lay the subfloor piece down (gently) on top of the adhesive. Then, pound the edge to insert the tongue fully into the groove. Then, set one screw into that corner. By this time the other end will have come loose, so pound that end back into position and set a second screw on that end. By now, everything is stable, you can stand on top of it, and run in the other 23 screws per piece, all the while sweat running down into your eyes, and then dripping off you nose onto the subfloor. When all that is done, lay down on top of the subfloor piece and look underneath the edge to see how many of your screws didn’t hit the joist; remove and replace accordingly.

At the end of each day of putting down subfloor, I paint it with exterior grade latex paint to protect it from the weather as it will be awhile before I get this thing in the dry. The color wasn’t my choice; it was five gallons of mistinted paint from Walmart (half price). About half the subfloor has two coats of paint on it. The first 5 gallons has done about 800 sq feet of subfloor

There are half inch holes drilled in the subfloor where water ponds after rainstorms.

I put all my spare, black 6mil visqueen down on the ground to start killing the grass and weeds inside the crawlspace. Where there isn’t visqueen down, I’ve sprayed the snot out of it with RoundUp. So, as desired, the inside of my crawlspace is beginning to look like a desert.

As of right now (June 8, 08) I’m about halfway done on the subfloor and about ¾ done with the joists. I hope to finish them both before June is over so I can get on to building exterior walls.