I know I may get crucified for this but I have a bit of a dilemma and need a more expert opinion than the people I've talked with. I have a slab on grade house built in the 1950's. I'm assuming there's no vapor barrier below the slab. I did duct tape a vapor barrier in a couple locations and have not seen any condensation on it so I'm pretty certain that I don't have a moisture issue that I need to be too concerned with. That being said, I would like to place a wood floor on my slab. The wood floor is solid wood from the 1950's I think. With the construction of the rest of the house, I realistically can't put in a subfloor. I know glueing solid wood flooring is a no-no in most cases but is there a case where I can do it? Ideas that I had come up with were gluing either a vapor barrier or 15# felt down and trying to glue the floor on top of that. Another was to float it above a vapor barrier or felt and glue the wood planks together like old time pergo flooring. If there is a better idea, I would love to hear it. I konw I've mentioned that I don't think that moisture is an issue but I am still worried about it.

J

You cannot glue the T&G of a solid wood, and expect it to stay together.

You can glue down a thin milled solid wood, if you also use a moisture blocking system and adhesive.

Don't even think about gluing a solid ¾" thick wood!!!!!!!!!!!!!!!!!!!!!!!!

Franklin makes a lifetime warranty concrete moister barrier(2 part epoxy that is really stinky)but with 2 coats you get lifetime warranty..and you can glue to it....solid wood no thicker than 5/16 to 3/8. I've glued down 1/2" but it makes me a little nervous in the summer w/high humidity.

thanks,

I actually talked with a guy from nofma and he said that it was possible and referred me to Bostik Finley and Stauff USA. They both make an adhesive that can be used to glue the solid wood floor to the concrete - even up to 3/4" thick. It's relatively new to the US, so if anyone ever comes across this situation it is possible to do now. They also have a lifetime guarantee with their products.

Thanks for the comments.

J

The age-old debate: to glue solid hardwood direct to slab or not... I have a current client freaking out about his slab calcium chloride reading some "6%." This is on the second story and it has been in for 4 months with and climatized (A/C, etc.). If I use the MVP then Bostiks to glue direct, I feel I will be fine as the other plastic-test method has shown no indication of excessive moisture. I have found practically that adverse movement of my solid plank floors occur due to drastic changes in moisture of the sub floor versus actual moisture content. I am confident the 6% will stay 6% thereby alleviating excessive movement. What do you think?????
Thanks!

Well, this is somewhat true. But if the environment humidity levels change dramatically, that wood will gain or lose moisture, which will effect it's size. Ever hear of the greenhouse effect? NOFMA has been telling people forever that it is normal for flooring to contract in the winter and show gaps, and expand in the summer to close those gaps up. It's NOT the subfloor moisture content that is changing and causing this; it's the relative humidity levels in the environment changing and causing the wood's moisture content to change. So, both the subfloor moisture content AND the relative humidity levels effect the moisture content (and size) of of solid wood flooring.

You have to have a brave soul to glue down solid 3/4 direct. You also really need to use shorts. It's a real sob to keep the bow out of even 1/2" thick solid glued dirct to concrete. I recently laid some myself that was a 1/2 solid and wouldnt do it again took me two days to lay 300sf and I half way think I know what the hell i am doing.

Thank you to both of you! Clearly movement is due to environmental conditions among many other things (quality & drying of the wood, acclimation, sub floor conditions, installation methods, stability of the climate itself, etc.). These things are always factors I need to drill into my clients before even taking a job, particularly here in S. Florida where they ONLY look at the humidity of the air if that makes sense. Great input and it makes more confident on this job.

On the 3/4" or 1/2" glue-down... Everyone seems to think it is "cheaper" for us to glue down plank floors b/c we aren't doing the additional step of plywood. However, like you said, the time & aggrivation of doing it along with the very costly Bostiks increases costs (for us anyway) substantially. Plus I HATE doing the work! We have had great success for years gluing down 3/4", 5/8", and 1/2" thick plank floors-- even 15" wide pine in South Florida. Still stable after years. That doesn't mean we prefer to do it-- I discourage it every chance I can, as it truly puts you in that point-of-no-return nightmare should any leaks or damage occur and it is very laborious. The lengths-- a bear when over even 8' it seems.
Thanks again. Enjoy your beautiful weekend!
Kelly

Gluing down wide long plank, is a task of frustration!!!!

Once all that surface hits the glue, it is fun trying to get the plank to move enough to get the t&G engaged.

Last one I did, I had to break out the strap clamps, to help my rubber mallet move the planks into position.