The Great Flooring Saga – Part 3

Repairing the subfloor.

With the old flooring removed, and the new flooring acclimating to the space, it was time to prep the subfloor for the new hardwood.  The first step was to get a moisture meter, and I got this one at Lowes:

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The reason for this is that your hardwood floor can absorb moisture from a subfloor that is too wet, and this can lead to your brand new (expensive) hardwood boards warping or cupping once they’ve been nailed to the floor.

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Most hardwood manufacturers state that 12%-13% is the maximum acceptable moisture level in the subfloor boards, and you should check throughout your house and keep a log of your readings. The moisture meter has two small pins that you push gently into the plywood and the reading is almost instantaneous.

Most of my house was fine.

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This area in the master bedroom, however, was problematic:

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The moisture meter read as much as 15.2 or even 16 in some places!

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The first thing to do is address what might be causing a moisture problem and make sure that’s stopped before you proceed.  I knew my house had some roof problems in the past, but a new roof was installed three years before I purchased it.  So perhaps the problem originated there.  The other potential culprit was the windows or the crawlspace. I’ve been in the house several times during rain, and the windows don’t leak, plus my inspector was confident they were weather tight.  However, what my inspector DID point out to me was my crawlspace.  It’s bare dirt and gravel under there, and in this room some of the insulation under the joists was sagging and had absorbed moisture.

All crawlspaces should have thick plastic sheeting (at least 6 mil) installed on the flooring and partially up the foundation walls.  Also, your floor insulation needs to be dry, adequately rated, and properly installed. (Mine wasn’t, and that’s a whole other post, coming soon.)  I knew this was an issue when I purchased the house but didn’t initially connect it to my floor issue.  However, I quickly realized the issue and my favorite handyman Dennis is remedying the situation. The only thing that remained was addressing the plywood in the subfloor itself.

I decided to remove the wet plywood and replace it with new. I started by cutting a small hole with my Dremel velocity, in order to give me a starting place to pry with my crowbar.

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Then I cut along the edge of the wall with my Dremel, so I could cut the large sheets of plywood into manageable pieces and remove them.

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I got much closer to the wall with the Dremel, though I did use a circular saw set to the depth of the plywood for speed on some of the larger, more open cuts.

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I had a friend come help me do some of the prying and cutting.  (Hey, fun excuse to learn new skills and play with power tools!)

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And I couldn’t resist the opportunity to pose while standing in my crawlspace, through my floor.

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But I discovered something problematic when looking at a scrap piece of plywood that we pried out of the subfloor.  Standard subfloor underneath hardwoods is 3/4 inch.  This was distinctly NOT.

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The discovery so shook me that I called it a night early and went home with my brain spinning in circles.  Would the floor be strong enough?  Would I deal with never-ending squeaks?  Could I lay more plywood over top?  (Spoiler alert: enough plywood to cover the entire house with an extra layer would be over $1000.)  An overnight spent obsessively reading flooring and woodworking forums assured me that while I might risk some squeakiness, it would be strong enough to hold and that it isn’t uncommon to find hardwood installed over 1/2 inch plywood in 40 year old houses still going strong.

The same reading convinced me that I probably wanted to use roofing felt instead of rosin paper for extra moisture retarding factor and also for a thicker surface to help ward off squeaks.

What I decided to do in the end what cut out the plywood that was too moist, and reinforce the spans across joist with 2×4 boxes to make it a bit stronger.

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The reason for the boxes is this: the horizontal spans in between joists where one piece of plywood joins another tend to flex, and offer no place to screw in a new board.  With these boxes, I could screw in new plywood around all four edges.

With only a few hours each evening available to work, since I still have a full-time day job, it took multiple days to get this done.  And in one corner of the room, I encountered something very interesting.

What’s wrong with this picture?

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If you said that the joist pictured has been cut and doesn’t appear to be properly supported or sistered, you’d be right.  Whoever said old houses are constructed better than their newer counterparts hasn’t seen my house.  In the end, I decided to make another framework of 2x4s to join the cut joist to its surrounding joists and help share the weight.

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Finally, after days of nervously leaving my subfloor open to the crawlspace, I had enough of the supporting work done so that I could cut replacement plywood to size to put back in place.  View the glory of my chicken scratch handwriting as I drafted measurements to minimize wastage of each sheet of plywood:

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The beauty of this being the subfloor meant that I could label each piece with my pencil to help me put it in place later, as it will never show underneath my hardwoods. I ripped the boards to size with a circular saw, and used the scrap blocks from the skids my flooring was delivered on as a makeshift saw horse.  Yay for reusing things!

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Boards cut, I glued them down along the seams with subfloor glue and screwed them down with 2 1/2 inch #10 screws.

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I didn’t know there was such a thing as subfloor glue even a few weeks ago, but I’m hopeful it will help reduce squeaks.

Next time, leveling the floor, laying down the felt paper and starting to lay the hardwoods!

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