Hi everyone - this is my first post here so bare with me if I am not following certain rules.

We are currently interviewing flooring companies to install 3/4 inch solid hardwood floor over concrete. We got different opinions in terms of how they can be installed. One says you can seal the concrete and glue down the solid wood floor. The other says because the wood floor is not rift or quarter saw, they can’t be glued down and requires plywood subfloor.

I searched online and didn’t see any mention of how saw type could affect method of installation.

If I use bostik mvp4 plus their glue, is it possible to directly glue down the floor? Or do I have to do plywood?

Typically for hardwood over concrete, you switch to an engineered product, not a solid hardwood product. You can absolutely glue down solid hardwood boards, however, its not recommended for larger spans (its OK for a 40-60SQFT basement hallway but I wouldn't do a 300SQFT room)

If you haven't bought the wood yet, just ask about switching to an engineered product with the same stain and finish. Most suppliers have both options available.

The main reason if for seasonal expansion and contraction - with solid hardwood over plywood, both the floor and subfloor expand and contract together with changes in humidity and moisture. With concrete subfloors, only the hardwood floor will be affected by changes in humidity, so you switch to an engineered product which has less overall susceptibility to expansion and contraction.

Really appreciate your reply! I wish I have the option to use engineered product but unfortunately previous contractor didn't inform me the difference and I ordered the wood through her, and there is no way for me to return/switch them at this point.

So assuming I am stuck with the solid hard wood here, would it be a problem with proper sealing of the concrete (using vapor barrier) and then glue the floor on top of that? Sounds like even with plywood this might not work?

How big of an area do you need to cover?

Remember you'd have to glue the vapor barrier down as well so you'll need double the glue (though you'd use a smaller notch trowel for the underlayment, so not quite double). It would have to be a full spread with trowel, so just the extra cost of glue may make the plywood option easier to consider. Typically a glue down floor uses either cork or rubber for the underlayment, a foam underlay won't work, nor will just the paper.

Then again, you'd have to glue the plywood down too so its a toss up.

Did you get installation instructions with the hardwood you bought? Call the manufacturer (google the number) and ask to speak to a technical expert regarding installation method and they can give you exact instructions on how to make their product work with your project (or advise you do go a different route).