We've been experiencing an issue across the floor on one half section of the house where there are discoloration spots across the floor. Moisture meter reads high- anywhere from 40-80% on spots with discoloration and 8-20% on rest of floor. Floor sits on concrete slab. The material of floor is Engineered Wood.

What baffles us is there's no plumbing underneath floor- all plumbing is above ceiling. Even irrigation drains run around the house, i.e. on sides parallel to house not directly under floor. There's no buckling of floor/seams or uneven ness.

So I'm looking for some help to find out what could be causing this issue. Any help is appreciated.

See pics (sorry for reflection from sun). enter image description here enter image description here

  • Is slap on ground? Imagine drains not doing as good of job as you hope, or might have partial blockage.
    – crip659
    Commented Feb 12, 2021 at 0:01
  • @crip659 yes its concrete slab on ground. confusion is these spots are in area that i'm not sure would have any drains running under slab. theres no bathroom kitchen etc within 12-15 foot. albeit there is some minor discoloration near bathroom area also but its not unique to that area. its spread out all accross section of floor
    – AKN
    Commented Feb 12, 2021 at 1:59

1 Answer 1


So you must realize that although there is no standing water anywhere on the ground below the floor there is moisture (a vapor). Concrete can be thought of as a sponge in that it will absorb moisture (water) and allow it to move through it.

Most concrete slabs have a plastic vapor barrier (sometimes) installed on the ground, but not always. If the wood floor was glued to the slab and moisture is transferring from the ground this is what is causing the water stains and there is no easy fix.

On the plus side the wood is not swelling (looking at the photo's) and the staining appears to be limited (although it's hard to see). Perhaps a darker colored floor stain would hide the marks. Is the wood becoming loose or warped?

  • Correct there's no swelling warping bluging or caving on the planks. Thats an interesting idea to stain the wood a darker color. I wasnt aware engg. wood can be stained. You mentioned 'no easy fix'. So what is the or a fix though?
    – AKN
    Commented Feb 12, 2021 at 2:45
  • 1
    a barrier of some sort below the floor. this would entail complete removal of the wood floor (not an easy or inexpensive job). How long has the floor been there? how old is your house?
    – ojait
    Commented Feb 12, 2021 at 3:30
  • 1
    @AKN-solid wood flooring can be refinished relatively quickly by professionals. It may be prudent to verify moisture under the boards by removing an outer edge plank. Tape a piece of cellophane (plastic) to the concrete and check for condensation build up each day.
    – ojait
    Commented Feb 12, 2021 at 3:35
  • House is approx 20 yrs old and the wood floor was put in about 6 yrs ago, so not that terribly old. From what we were told by prev. owners, they did put the concrete sealer before installing flooring.
    – AKN
    Commented Feb 12, 2021 at 3:42

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