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Plywood under wood floor on slab foundation?

Posted by marti8a (My Page) on
Tue, Mar 6, 12 at 22:37

We're getting ready to add on a dining room, and are doing a little kitchen remodel at the same time. Kitchen has 8 inch white tile, in fair shape but dated.

We had engineered wood floors put down in living room several years ago, and it is not holding up well.

I've been looking around at floor options for the kitchen and dining room and the smaller flooring stores have been telling me (for wood flooring) that the flooring will hold up better if it has a plywood layer under it.

NO ONE locally told us that when we put the engineered floor down. We are in central Texas, and a friend in NC whose husband does repo repairs said it is common there.

So, is it necessary? Is it better? Worse? Why?

Follow-Up Postings:

RE: Plywood under wood floor on slab foundation?

That has been a common approach here when homeowners want to put down solid wood on slab. However, 10 years later when it's all rotted out from the moisture migration from the slab, they usually have learned their lesson.

The new addition should be constructed with a vapor barrier under the slab, but the old one probably wasn't. That makes using the same flooring a bit more problematic, as well as the potential for levelness issues between the two structures.

Unless you're putting down pressure treated marine grade plywood, just using a good trowel on vapor barrier and gluedown engineered wood flooring is sufficient. Or you can do a floating floor with a vapor barrier under it, which might be the better approach since you are wanting to do the same floor in two separately added home sections.

RE: Plywood under wood floor on slab foundation?

The house was built in 1983, but not by us so I don't know if it has a vapor barrier under slab or not. The house was wrapped with a barrier, so maybe.

What is the name of a trowel on vapor barrier? Is it thick like thinset, or more like glue?

RE: Plywood under wood floor on slab foundation?

Get a real RH reading from your cement. That will determine the facts. Then if RH is fine...use a urethane (top quality adhesive) and glue down and roll an engineered floor. I assume there has not been any movement. With that said, I would like to hear more about the engineered not holding up...what that statement means as that could have a further bearing on any advice given.

RE: Plywood under wood floor on slab foundation?

Yes, a reading was done before the first floor and was ok. We have had some movement in the foundation but not at that end of the house.

I think the problems are partly because the flooring wasn't acclimated before being installed. It was in December, and the flooring was brought out here and installed the same day. I don't know where the flooring had been stored before it was shipped to the floor store, or how long it sat in their warehouse before being installed.

It is a Mannington Hickory, and at first it was just checking, but now we have a hump where it is no longer glued to the floor and raised up.

After the checking, I posted and other people posted about the same problem with that floor. The floor store owner came out and said it was a problem with the floor. Mannington sent a rep out and of course it wasn't the fault of the floor, and then the floor owner agreed with them. So we were the big loser there.

And we wanted to buy from a local store so we wouldn't have any problems. Next time we do it ourselves.

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