Saturday, September 22, 2012

Follow-Up--And Fall-out--From the Floor

The last post was about the work done to repair the kitchen floor framing.  I have ended up doing more on it since that writing (with a lot of paying work in between, which is why I didn't report this sooner).

Because of the condition the original linoleum was in, we had to give up on it.  Torn places, splits (nailed down, in the middle of the room).  And the 1/2"  plywood underlayment beneath it felt spongy.  Once the linoleum was scraped off, we saw why it felt like that--years of any water that got on the floor puddling in the sag had caused the plywood layers to separate, as well as rusting a lot of the nails.  I ended up peeling off the layers of the plywood in the kitchen, the back entry, and the half bath between the kitchen and the front corner bedroom.

That left the original board subfloor.  Construction methods of 1950 called for framing the floor, then putting diagonal 1x6 boards across the joists for the subfloor.  This was not high-quality lumber; since it would not show once the finish floor was laid, they used #3 grade, the lowest used in construction.

In the 1950s the use of plywood subfloor material displaced the old board subfloor.  And even though carpenters are a conservative bunch (many seem to try to spend their entire career doing things the way they learned to when they started out) they adopted the plywood system pretty quickly, because it was safer for them.  No. 3 lumber can include large knots in the boards, and if someone steps on these knots, especially when carrying something heavy, the board can break at that point.  Some of the older carpenters ended up with scars up and down their legs from breaking through those old board subfloors while the house was being completed.

And this board subfloor had not been helped by the years of puddling water above, and several years of water in the basement below.  There were rotten boards under the sink, broken boards in various places in the kitchen.

I couldn't remove the entire subfloor, because it runs under the walls, outside walls as well as inside.  But I marked lines on the two joists closest to the back wall and the opposite wall, and set lines about two inches out from the other two walls.  I repeated this for the bathroom and the back entry.  Next step was to work along the lines removing any nails in the path of the cut with a cat's paw and hammer to pull them up, and end nippers to pull them out.  Then I set the depth of cut on my power saw to about 7/8", slightly more than the thickness of the boards, (the cut line is barely a scratch on the top of a 10" deep joist, and because of unevenness in the boards often even less than that.).  I went around the room cutting the lines.

By the way, as a safety precaution I was using scrap plywood pieces as a work platform while I did this, to keep from going through the floor myself.  If I had to walk across the room, I tried to always step on a joist location, not on the boards between.  One of our friends had come over to see the place and didn't see why I thought I needed to replace the subfloor--until he stepped on a weak spot and felt it crumple underfoot.  He wasn't hurt, but after that he understood.  It's a bad feeling when you step down and the floor cracks under your feet.  And when you're busy working and thinking about what you're doing, it's hard to remember to only step down on the joists.

So I peeled out the boards with cat's paw and nippers, finished the cuts in the corners with chisel and handsaw when I had to, and as soon as I had a large enough area, I put down the first sheet of 3/4" plywood.  Because of the old wood joists I used decking screws, 2-1/2" long, to put down the plywood.  The screws hold better than nails, and with it all down there is no hint of a squeak from any of the new floor.

I did have one unpleasant surprise when I took out the old boards.  I had sistered new joists onto two of the old floor joists as part of the jacking work.  Now I found one more, between those two, that had cracked from the stress of jacking, even though I had taken it slowly.  And this was not a lengthwise split, but a vertical break in the joist about 8" to one side of the beam, starting at the top and ending about 2" from the bottom edge.  It had happened when I jacked the floor, but I didn't see it from below--partly because of the temporary lighting I was using was shining on it from below, but partly because the crack was widest at the top of the joist.  Effectively, that joist was no longer a 2x10, it was now a 2x2!  (That's why you have to be careful about cutting into framing members--a cut can reduce the effective size of the joist.)  The upper portion of the joist was now only along for the ride, it could no longer give any structural support to the floor.  So, another trip to the lumber yard for joists to sister alongside it as I had the others.

So we now have solid flooring in these areas, a firm platform for the rest of the work to be done.