Hardwood installed, subfloor too thin, help!

smon · Sep 30, 2009

Hi -
Can someone help me with ideas to remedy an improper hardwood installation. I have a lot (1500 sq ft) of new 3/4" hardwood that has been installed in my ranch house. However, it turns out the subfloor is only 9/16 OSB instead of the recommended 3/4" minimum. Now, after only two months it seems many of the boards are popping up at the edges. I'm assuming this might be because the subfloor is too thin to hold the staples properly and/or flexing in the subfloor might be making it worse.

I really don't want to tear up the entire floor in order to lay more subfloor. Any ideas?

(I have an unfinished basement, so it might be possible to add cross blocks between the joists to help strenghten the floor)

Also, would it be a good idea to use crews from below (up through the subfloor and into the offending boards) to help keep the boards down.

Thanks!

Daniel Holzman · Sep 30, 2009

You should post some pictures, I have no idea what the term "popping up" means in the context of your post. There are many possible explanations for failed hardwood installation, however to make any progress deciphering the puzzle you need to tell us the type of hardwood, and the exact details of the installation, including type of nails or staples used, whether glue was used, were the boards conditioned before installation, how are the boards finished, was a gap left around the floor, how the subfloor is attached, what the subfloor is attached to (i.e. joist size, length and spacing), moisture conditions in the house (are you air conditioned, where are you located). The pictures should show the specific damage to the boards, are they cupped concave or convex, are they out of level, are there gaps. Then we can begin to analyze.

smon · Sep 30, 2009

Thanks for the quick reply!

I'll take some pictures and find more specifics, but here is an attempt to answer some of the points you brought up.

Specific Problem: It's not that complete boards are bending or warping. It is that there is a ridge between the boards. In other words, one board will become slightly higher than the next one and if you run your bare foot along it, you can feel the ridge or slight change in height. This is very small (maybe 1/32") but it is noticable and it seems to be getting worse. By worse, I mean more boards seem to be getting this way over time and also it is seems to be getting more pronounced. This is occurring along the long sides of the boards and not as much along the connecting ends of the boards.

Installation: There is a 3/8" gap along the walls, so it doesn't appear that cupping due to expansion is the issue. The boards were acclimated for about 10 days and the house is air conditioned. Although they were installed in the middle of the summer heat and humidity and it is now changing to fall.

Material: The hardwood is BR-111, solid brazillian cherry, 3/4", pre-finished, with micro beveled edges. It was installed with 2.5" staples using a pnuematic floor stapler.

Subfloor: The floor has 2x8 floor joists at 16" OC. The hardwood was installed perpindicular to the floor joists.

Hardwood installed, subfloor too thin, help!

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