I installed 3/4 OSB directly over a concrete slab, with a vapor barrier

Q imported from our old site, Face Lift Floors: I installed 3/4 OSB directly over a concrete slab, above grade, with a vapor barrier Rosen paper and Nailed down 3/4 Maple (Canadian!). What problems can I look forward to?

A: I am not a big fan of installing nail down products on “chipboard”. I know that some if not all hardwood manufacturers will not warranty one of their floors if it is installed on this product. Problem is, it doesn’t hold nails well. Since you have installed this directly on the concrete, which I assume is fairly level, you may not have a problem with boards coming loose.

The bigger concern at this point would be moisture or dampness. If there is any problem with this, you will likely get cupping of the floorboards, with the edges raised higher than the center. Maple is more susceptible to environmental changes than oak, for example. If this happens, it will stretch out the nails a little, then it will likely fluctuate in moisture content, and shrink. Then you could have considerable gapping between boards.

The time to ask the question you asked is before you install the floor, not after. However, let’s hope there are no moisture issues in your basement and you won’t have any problems.

Original / moved link https://faceliftfloors.com/q-and-a/rosen.php

Should a water vapor barrier be put down if the hardwood flooring is to be installed over OSB

Q imported from our old site, Face Lift Floors: Should a water vapor barrier be put down if the hardwood flooring is to be installed over OSB over a full unfinished basement? How should the flooring be laid? Parallel or perpendicular to the floor joists? Why?

A: I will give my opinion here. When one talks about installing hardwood in a basement, it can be a scarry thing. Moisture is an enemy of hardwood. My first point is this: I know of no solid hardwood flooring manufacturer who will warranty solid wood installed below grade. You have not told me what you are installing, so I want you to be aware of this. There are laminates on the market designed to be better adapted to this environment.

By OSB, do you mean chip board? I would never install a nail down product to chip board. An easy test for moisture from a basement floor would be to tape plastic squares to various areas of the concrete and left for a day or so to see if condensation develops on the plastic. Even if it doesn’t, a vapor barrier is not a bad idea.

One thing I would recommend in the construction of the subfloor is this: Build it in such a way that air can flow up and down between the joists. You may wish to include a couple or several vents in the floor surface to accommodate this. I say this because, if you ever get moisture under the subfloor, it can linger a long time without proper venting.

More often than not, it is best to run your finished floor across the floor joists, since this will increase structural stability, the floor joists bearing most of the weight of the finished floor, rather than the plywood or OSB subfloor.

Original / moved link https://faceliftfloors.com/q-and-a/vapor.php

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