First floor subfloor

Last week I ordered 48 sheets of Advantech sheeting for the first floor subfloor. I’ve tried to get a good deal on material for the subfloor, but the guy I’ve been buying lumber from hasn’t had any Advantech for a while. He offered to get what I needed from his supplier at his cost which ended up being about $2.50 per sheet less than what I would pay elsewhere.

I picked up the material on Sunday so that Jon, Dad, and I would be able to start putting down the subfloor on the main level of the house yesterday. I spent a couple of hours getting things ready Sunday afternoon, moving things out of the house and smoothing out the ground under the house – I needed to put plastic in the crawl space.

So, on Monday morning, we began by caulking gaps along the sill plate and boxing on the foundation walls, a job that was partially done last week. When we ran out of caulk (we were most of the way around, and I bought more caulk at lunch time so we could finish the job), we started putting plastic on the ground in the crawl space. I bought some 6 mil black plastic on Sunday for this purpose.

The plastic comes in a 20 foot width. So, we rolled out enough to go from the front to the back of the crawlspace with a little to curve up onto the wall. We had to cut it to get it around the piers the timber frame sits on. We securely taped it around each pier. It took two widths to cover the main part under the house. We taped the seam together in the middle where the two pieces met.

After putting plastic down under the kitchen and under the mudroom, we began hanging radiant barrier insulation along the crawl space walls. This is a reflective material with bubble wrap in the middle. The idea is to hang it from the top of the crawl space wall so that it hangs down and curves out onto the plastic. This material’s insulation value is not diminished if it gets wet (I don’t want it to get wet, of course) unlike fiberglass insulation. It should help to keep the crawl space temperature moderated and allow us to capitalize on the thermal mass of the earth below the house. If we insulated under the floor, this wouldn’t be possible.

I learned of this method of insulating a crawl space from an insulation contractor in the St. Louis area on a forum a few years ago when researching what to do for our house. He claimed that his experience is that the temperature in the crawl space is maintained within 10 degrees of the temperature inside the house.

Once we insulated the areas that were already caulked, we began putting down Advantech sheets for the subfloor. We had to cut around timber frame posts and modify lengths because I hadn’t laid out the floor joists in the frame as I should have. However, the process when quite well. By the end of the day, we had finished the floor in the timber frame and also the kitchen area.

We’ll put the floor down over the root cellar and in the mudroom area on Wednesday. We also have to put floor down on the straw bale wall toe-up all the way around. There’s also one section of porch floor in what will be the summer kitchen that needs to be put down. We should be able to finish all that on Wednesday and start putting in window and door bucks, too.