Hello all, I'll be laying my first hardwood floor sometime in the next couple months. It'll be around 1000 sq ft on a new slab. I'm planning on using 3/4 T&G, probably some exotic that is reasonably hard (dogs and kids). I've searched out and read some of the relevant history here but still have a few questions. I'm in Central Florida so summertimes are very humid and the humidity is fairly high year-round. Hopefully I'll be putting the floor down before the rainy season starts. Here are my questions:

1. I'm supposing I should wait until the AC has been running for several weeks before bringing the flooring into the house?

2. The slab is definitely not flat but I haven't actually measured it yet, so I'm planning on a self leveling treatment and treating with "Lockout" or something similar before putting down the polyethylene. The question is will the Lockout affect the leveler?

I'm sure I'll have more questions as the time gets closer so I'll thank everyone in advance and hope you'll forgive my naivete.

For one thing, many of us do not recommend gluing a solid directly to concrete, especially a 3/4" solid. You might get by with a 5/16" by BR-111 and a moisture barrier like "Lockdown", MVP or sheet vinyl. I know some have done that and BR-111 says you can do it with a moisture barrier. For a solid, I'd use MVP and Bostick's Best instead of a waterbased adhesive like Taylor 2071 and Lockdown. Just my opinion.

This isn't going to be pretty!


¾ directly glued to the concrete, is very, very risky. Think Overkill if you insist, on doing it and don't throw a fit if it does cup later.

I don't believe Taylor Lockdown, is compatible with any other adhesives but Taylors. 2071 is going to do a number on that solid wood.

Are you securing 3/4" plywood the the slab?...then nailing?.

Gary,

While we're on the subject of Lockdown, would you reccommend using this product in addition to using the 6mil poly if I use the 3/4 CDX plywood screwed to the slab? My moisture test, using 2x2' sections of plastic taped to the slab produced no moisture, so I think I'm ok here.

Also, you're talked alot here about using vinyll flooring as the mosture barrier, then gluing and screwing/nailing the would to the floor. From you're experience, what is the general cost per sq ft. of this method, including adhesive and vinyl? 

Thanks...Stan

Let's back up here a little. I had tried various moisture protection systems under plywood for quite a few years. I tried two layers of 15 lb. asphalt felt glued with cutback adhesive. That worked but it was time consuming and the cutback smelled and took a long time to dry. I tried gluing the 6 mil poly down but that is a royal PITA. Ever try spreading thick goo on sheet plastic?I didn't care for that method. So I took a clue from the engineered flooring manufacturer's recommendation of gluing down inexpensive vinyl for a vapor barrier. I reasoned that if it would work for engineered hardwood, it should work for plywood as well. I started using this method about 8 yrs. ago and have never had a moisture problem with the solid hardwood I have installed this way. Now I'll bring us up to date. In the last few years, Taylor, Bostick's and Franklin all have made a vapor barrier that can be troweled on. I've done cost comparisons and the Bostick's MVP and Best combo is less money than installing vinyl and gluing the plywood to that. It also is a bit easier as well. So, if I am installing 3/4" plywood over concrete as a nailing base for solid hardwood, my choice in the future will be MVP and Bostick's Best. Or Taylor and their Lockdown. Or the Franklin system. I hear now that Dri-Tack has a VB and urethane adhesive as well. I would most likely go with the system that I could get the best price on as they all will most likely work well for adhering plywood to concrete. I still believe in nailing the plywood as well to make it lay flat in the adhesive till it cures. Hope I answered your question.

Gary wrote:
"I've done cost comparisons and the Bostick's MVP and Best combo is less money than installing vinyl and gluing the plywood to that. It also is a bit easier as well. So, if I am installing 3/4" plywood over concrete as a nailing base for solid hardwood, my choice in the future will be MVP and Bostick's Best. Or Taylor and their Lockdown. that Dri-Tack has a VB and urethane adhesive as well. I would most likely go with the system that I could get the best price on as they all will most likely work well for adhering plywood to concrete. I still believe in nailing the plywood as well to make it lay flat in the adhesive till it cures. Hope I answered your question."

Gary,

Great history lesson. I'm liking this installation method more and more than my original plan. If anything, the added moisture protection would be worth the investment. Thank you.

I checked out online the products you mentioned and love both the Bostick and Taylor product. For what I've gathered so far is that the Taylor's is less expensive from a price per sq. foot than the Bostick. For example, Bosticks MVP covers about 45 sq.ft/gal, whereas the Taylor Meta-Seal X-Treme Concrete sealer # 2012 ( http://www.WFTaylor.com/prod_descript.a ... it&pid=139 ) has a coverage of 400 sq. ft. gallon. I also like the fact that you can apply the X-Treme using a nap roller, as opposed to toweling on the MVP. In addition, the Taylor 2071 adhesive, depending on the trowel size and notch one uses, 60-250 sq. ft. gallon. The Taylor's 2071 is also a few dollars less per gallon than Bostick Best. What trowel size would one use on a project like this?

Using either product would increase my cost for installation about $300-$500, over the 6ply poly and CDX method, which is not that big of a deal for me. At the same time, the Bostick or Taylor product would, IMV, provide added protection against moisture issues.

Gary, you also said that you still screw/nail the plywood to the slab, in addition to using the adhesive to hold the subfloor in place until the adhesive dries. How many screws/nails per 4'x4' sheet would you use?

Finally, another thing to consider if adhesive is used is when it comes time to sell the house, (or my family), the new homeowners may want to remove the whole flooring system and in that case, once the plywood is on and screwed in place, it's not coming off. Whereas, with the 6ply poly and CDX method, after remove the flooring, all one would need to do is back out the screws on the subfloor. But I guess why should I care at that point. I'll be dead and gone, by then.

Thanks again for all your input.

Best...Stan

When gluing the 3/4" plywood down, I often kerf the backside to allow the plywood to conform to the slab better. Since the adhesive is doing almost all of the holding, I'll only nail here and there to anchor the plywood and eliminate any hollow sounding places. I hand nail with a 2 lb. sledge and 1&1/2" fluted masonry nails. Works great! Always use the adhesive manufacturer's trowel size recommendations. Often, for 3/4", they recommend a 1/4" x 1/4" notched trowel. This uses lots of glue and you'll only get about 40 to 50 sq.ft. per gallon. But always go with the recommendations. And IMO, no one is going to want to remove a 3/4" solid hardwood installed over 3/4" plywood over concrete. Why would they want to do that? Because they don't like hardwood? Then cover it with area rugs! That's what I think anyway.

Sound good, Gary. Two last questions and I'll get out of your hair.

Will using a 1/4" x 1/4" trowel to apply the adhesive add 1/4" height to the floor, or will some the adhesive be pushed into the the 3/8" groves on the back of the plywood? I'm already maxed out on floor height. With the extra 1/4" height, I would begin to have height issue on some of the doors and windows. Finally, do you apply the adhesive to the floor or "backbutter" the plywood and then apply the plywood to the floor?

I lied. One more question. If I were to stay with my original method of 6mil poly, subfloor screwed to slab what is your opinion on applying MVP to the slab as an added measure?

Thanks again for all your help.

Best...Stan