We are planning to put carpet over an oldish hardwood floor. I noticed that the floor has a dip of about 3/8" in a few areas. I intend to measure around with a long straightedge and see if I can find any worse spots.

The dips are about 6" across by 3-4 feet in length (coincide with a once-removed wall). There's no structural issue underneath (basement) so I'm only concerned about the effect on the carpet - how it looks, wears, and avoiding a trip hazard.

Is this size dip bad enough to do something about? If not, what is generally considered to be the maximum allowed variation in the floor?

(If it is enough of a problem, I intend to fill with strips of 1/8 or 1/4 hardboard or plywood or similar.)

  • 1
    Think if it is a wall to wall carpet you want to have a flat surface. Wall to wall is usually stretched so it would be floating above low areas, so walking on it will cause it to be pull/push down increasing wear. – crip659 Mar 22 at 18:03
  • 3/8 is a lot. Not just a trip hazard, people can lose their balance when the floor is not where they expect it to be especially when bare foot or on wobbly chairs. If there is an area that is consistently low everywhere fill it with a suitable piece of plywood. Then cover the entire floor with another thin layer. – jay613 Mar 23 at 8:07
  • The question, as it's phrased, has no right or wrong answer. It's a matter of opinion and there probably aren't any standards outside of ADA rules or similar. – isherwood Apr 22 at 21:18

Levelling compound is your pal. Use it to get the whole floor level. whatever else you do will come back to haunt you. Whether the carpet is free standing or stretched wall-to-wall, it needs to be on a flat, level surface, with no dips deeper than 1/8" over a square foot - and that's pushing it. Underlay may give a little leeway, and indeed, is worth putting down first, but won't solve your problem.

  • I had thought (probably incorrectly) that self-levelling compound was meant to be used over something like concrete; since this is a wood floor, is there a specific type of compound that should be used? I assume it needs some flexibility. – StayOnTarget Mar 22 at 18:15
  • That's the way I'd go. But that's me. Another solution would be to use hardboard sheets, over the whole area, which would level up quite well, and in places where the dip was deep, put enough hardboard under the sheets to take up the slack. – Tim Mar 22 at 18:18

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