Plywood Subfloor High Spot


Old 09-21-14, 07:58 AM
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Location: USA
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Plywood Subfloor High Spot

Hello Everyone,
I am installing laminate flooring throughout my first floor on my 25 year old home. I am on my second room and have encountered a problem with the subfloor that I am not sure how to properly deal with.

The room is 12'x12' with a 3/4" ply subfloor on 2"x8" beams nailed and glued 16" on center.

It appears that 3 of the beams in the center of the room are slightly higher (1/8" - 1/4") than the rest resulting in a "hill" that runs through the length of the room.

I am inclined to score and sand the plywood through this "hill" to level the floor.

Is this the best approach for this type of issue?

Aside from this problem, the subfloor is strong with no flexing or squeaking.
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Old 09-21-14, 08:47 AM
czizzi's Avatar
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Join Date: Jul 2007
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Posts: 7,291
One high floor joists will throw off the measurements across the adjacent two joists making it look like 3 joists are an issue. Over the length of the room - that should then be parallel to the seams in the flooring. One way to address the bump is to sand as mentioned. You can also remove the plywood and plane the joist down. Or a third way would be to ease the bump out by feathering the floor out over a wider area so that the hump is more of a long slow smooth curve. Laminate's click lock mechanism does not like a lot of flex. By feathering out the curve, you prevent the up and down motion of the flooring that can lead to the click lock failure.

If it was me, I would remove the plywood, plane down the joists and re-install plywood. Sounds like more work, but really, it isn't if you have access to a planer. You can obtain an electric planer fairly reasonably at Harbor Freight for under $35.

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