Floor Fixing - Preparing for Hardwood

We bought hardwood to install upstairs in our spare bedroom a while back, then the project stalled out when we found ourselves on strike. After that the project moved forward just enough to see the carpet torn out and a rotten spot found along an exterior wall.

The rot scared me off the project for a long time, but I've decided to tackle the hardwood as much as I can, while patching the rot and then I can return to the problem spot as part of a bigger project. This blogpost will show how we patched the subfloor and prepped for hardwood, with the hardwood install following in a later post.

Meet the problem.This is the back corner of a closet. The wall to the left (being attacked by a crowbar) is the rear exterior wall of our house. The wall to the right backs onto the chimney, but is also an exterior wall.

A tiny air gap in the corner of the wall has allowed moist exterior air to come into teh house. Once inside the air is trapped by the vapour barrier plastic, and absorbed by the wall framing and floorboards.

In order to put the brakes on the rot, I needed to block the air infiltration, and in order to fix the floor I needed to replace the rotten plywood.

First order of business is to pull up the plywood and see how invasive things are.

Using just a prybar in the rotten sections, and a skilsaw in the solid wood, I removed the floor from the closet. This made for loads of little rotten wood flakes and some sawdust. It was tough fighting the nails in teh good wood, but the rotten sections just crumbled apart. 

With the plywood out, I used a handsaw to clean up the edges of the hole, and tidied things up. My next step was to stop up the airflow by using some expanding foam to fill in the gaps and holes. I boogered things up pretty good and left it to set up overnight. The next morning I cleaned up the over-flow and took this pic:

There was huge change once the airgap was sealed. Amazing how a detail like this can warm up a room! Ok, a closet. But still...

With the air gap sealed, I turned to installing cleats to mount boards on for the new subfloor to screw into. I found some scrap cedar left over from my shed build this summer, and predrilled holes to accept a 1/4" X 2-1/2" lag bolt. The ledger boards were lagged to the solid framing to give a spot for the subfloor to attach to. This was needed because when I cut away the subfloor, I missed cutting on a joist by about 5".  The cleats would create a shelf for a board to sit on to act as a support to the edge of the plywood where I had cut it away.

My helper started the lags in the cleats...

And then I installed them and the board for the subfloor to sit on.

If you look closely in that pic, you can see that I marked the top of the joists so I would know where the cleats are. This way, I was able to lag through the new board into teh cleats to hold everything snug and tight. The hardest part of this step was getting the board to sit in place and to pull it sug against the existing subfloor. Lag bolts acted as a clamp to pull things up tight. They were removed once everything was set up. 

At this point I was ready to start installing new plywood. Step one was to get a piece of tar paper and lay it into the space. I stapled it to teh floor to prevent it from moving, then using a utility knife, cut out the outline of the missing plywood.

The outline came out messy, but for the mostpart it showed the path I had taken when I freehanded the cut with the skil saw, and the imperfections in the house.

I stapled the template on a piece of plywood and took the whole thing out to the tablesaw. 15 minutes later, I returned with a nearly perfect patch for the subfloor.

When I came in, I found that my helper had marked up a scrap of wood I left out. It made me smile that he had copied my markings and on the opposite side had marked the board the way I mark them to go through the planer.

Anyways, with the patch cut, I brought it up stairs, used a jigsaw to adjust things a little, et voila - a perfect fit!

With things fitting so nicely, I was able to drive a pile of flooring screws into the patch and the surrounding boards to pull everything together , and I have a floor that is solid and ready for hardwood!

I will need to get a long straightedge out and mark high and low spots on the floor, then do some leveling and tightening next, and at last it will be time for hardwood!