RedGard with engineered hardwood floors, extra moisture protection

11 years ago

We recently had some water damage on our hardwood floors. We performed test after test and found no fresh water or sewer leak. We decided to remove the affected/damaged wood and break up a 2ft x 2ft piece of the foundation right where the wood was affected. We found nothing but dry dirt. It appeared as though the slab in this area of the foundation was thinner (about 2 - 2.5 inches) than it should be (3.5 - 4 inches). In order to protect the new floor we are about to put down, we have talked about putting down a hydro cement or concrete and on top of that putting redgard to insure extra protection? Can redgard be used on top of concrete, and then use a wood floor adhesive (Mapei) with a mositure barrier built in? What would you recommend here?

Featured Answer

PRO

Cancork Floor Inc.

11 years ago

Josh, I'm sorry this has happened. Moist areas in concrete that are affected "first" are common enough for even lowly "sales people" like me to know about them. Eventually the moisture would have gotten around the entire plastic barrier (because water likes to flow around things...it's what it does).

Plastic barriers can be pierced when pouring the cement. This is why concrete is tested eventhough the slab specifications state "moisture barrier". When it comes to cement slabs, you (professionals) have to ASSUME they have been compromised. You (professionals) have to test, test and then test again (there are 3-4 different tests available to professionals...ask for the results to PROVE the contractors tested) before installing anything directly to the slab.

Hopefully you have slowed the process enough to give you time to save for a new floor. If one area has been affected, you (home owner and professional) have to assume everything else will have the same issue given enough time.

I would push HARD to see the moisture testing results from your installer (dates MUST indicate they tested the slab AND the hardwood). I would also ask which adhesive they used and HOW MUCH. A GOOD installer will have these in a file that they can pull out at a moments notice. A not-so-good installer will scratch their head and ask, "What is it you are looking for?"

Just by how they answer these question, you will know which of the two you are speaking with.

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Comments (7)

PRO
By Any Design Ltd.
11 years ago
I would not recommend Red Guard used like that. I do not like Red Guard period and in that approach you are using it poorly.

Most of these membranes are designed to allow water up through them and block water going down.

I highly suggest you contact the wood flooring association of the USA. Start there.
PRO
Cancork Floor Inc.
11 years ago
When you broke up the slab, did you see a plastic barrier anywhere? If not you have a pourous slab = tremendous amounts of water resistant adhesives. Slab testing should have been done prior to the installation of the hardwood.

A pourous slab = eventual water damage. The appropriate intall = appropriate amounts of appropriate water restant adhesives that will "handle" the pourosity of the slab. The other appropriate install = floating floor.
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joshdurst
Original Author
11 years ago
A floating floor was not installed. The damaged area is concentrated in one area. The wood floor installed is continuous from our back door throughout the dining room, living room and hallway. To install floating floor, we would have to take up everything. We can't afford this, plus, the other part of the flooring is not damaged so I don't know why the slab would be different in those areas. This is all good info. I believe the true fix is a floating floor. I may have to wait and do this if we start to have more affected areas. As a band aid which, we hope is a lasting one, is to fill hole in slab to a greater thickness and put a thin layer of hydro cement on top of the affected area. Of course, it will all need to be level.
joshdurst
Original Author
11 years ago
But yes, there was a plastic barrier. It was very thin.
Janice Battaglia
8 years ago
What should be used under our wood flooring to protect the wood from moisture from the concrete?
PRO
Cancork Floor Inc.
8 years ago
@jbattaglia123 - how much time to you have? There are many ways to go about this. The expensive way is about $5/sf - with a solid guarantee. The *next best way is to use an all-in-one adhesive that is also a moisture barrier for $2-$3/sf (yep...it is that expensive).

Or you can float an engineered hardwood and use a plastic vapour barrier ($0.10/sf at Home Depot) and add some cork underlay for a bit of cushion ($0.40/sf).

The expensive treatment and the floating installation are the only two that have decent success rates. The adhesive version has failed in the past and will continue to fail because the USE of the product will depend on a human being....and we are always the flawed part of any equation.