I currently plan on purchasing some 3/8'' bellawood prefinished brazilian cherry 3'' planks. This will be installed onto on grade concrete (will put moisture barrier and 5/8'' plywood subfloor - attached, not floating - down before hand). I realize that 3/8'' is more susceptable to cupping, etc., then 3/4'' is but how much more? Is using 3/8'' going to be something I'm going to really regret? (keep in mind that I'll only be in this place for a maximum of 5 years). Also, is there anything special I should watch out for when installing the 3/8'' (never used 3/8'' solid before).

Thanks very much!

(also, what length fastner should I use, 1''?)

The thinner flooring is less likely to cup.

Less vessels to deal with and absorb moisture.

Cupping is because the bottom of the board is wetter then the top of the board.
Has nothing to do with thickness.

thanks much I was misinformed then. Given that, are there any significant negatives to 3/8'' vs. 3/4''

glue it with bostiks best moisture cure urethane. call their tech dept. and get a letter for the warranty. is this solid or engineered? why put wood subfloor down on concrete.

william,
thanks for the input. I'm using solid and I just don't want to mess with gluing down - never done it before and I'm at least familiar with nailing down. I also want a little more between my feet and the concrete. I'm still, conceptually having misgivings about the installation of the moisture barrier - I understand that I should use an asphalt mastic to glue down the moisture layer and then attach the ply overtop of that, should I glue a bit down at a time and basically glue it down as I lay the plywood overtop and attach it?(seems to make the most sense to me, e.g., if I glue all moisture barrier down at once I'll just be "squishing" out the mastic by walking around on it).

Is there any other less messy/quicker method for putting down a moisture barrier when I'm going to be using a hilti or ramset gun to attach the ply?

thanks very much!

ok,
a follow up to this: are there any conditions where one wouldn't necessarily need a moisture barrier? (I haven't been able to test the moisture content of the slab I'm installing this on yet). Are there some applications where gluing & shooting down 5/8'' ply and then layering roofers felt and floor on top of that would be acceptable? e.g., does one always need a moisture barrier on a concrete slab? - I'm really just trying to avoid the pita of gluing down a moisture barrier and then shooting into that.


Thanks again for all the great advice!

The floor will cup, way before the plywood rots!

If the slab is poured right with the right mix, and not too much water added during the pour(even if it is old), and the concrete was poured over a moisture barrier, with all landscaping sloping dramatically away from the slab, allowing excellent run off, and you have a slab @ 3-lb. per 1000 sq.ft. You may get lucky.
No sprinkler systems shooting on the sides of the slab daily, either.

Gluing the plywood down, works if the slab is not emitting too much vapor(vapor can not be seen, that's why it is called vapor)

But why not glue the thin wood down in the first place? What's the difference??

Have you thought about floating the subfloor and fastening or gluing the flooring to that?

floor guy,
thanks much for the input - I haven't yet had the opportunity to get a read on the moisture level of the slab but all landscaping does run away from the building and runoff should be good. I'm just a bit nervous that a floating floor would be "bouncy", especially since the flooring will only be 3/8'' (e.g. won't add as much weight to help hold things down). Would floating subfloor be more prudent in terms of a potential moisture problem?

I've pretty much decided that I need to do the poly moisture barrier anyway but I still have a question as to the process. From what I've read one needs to apply cold-cut mastic to the whole concrete subfloor and let that dry for 2 hours and then come back in and lay the plastic down, I assume then that it'll just be a huge bloody mess? Also, if I went the floating ply subfloor route, would it still be necessary to fix the moisture barrier in place with mastic? And finally, would adding an additional layer of roofers tar paper over the plastic before the ply goes down offer any extra protection or is it just not worth the time and money?

Thanks very much and I really appreciate all the input!

When buying from lumber liquidators make sure all the wood is from the same mill and has the same date, the mill I.D. is found on the top right of the label and will be initials like JUR or BWP.
If you mix different mills or even different dates from the same mill you are not guaranteed the finish will be the same or if the tongue and groove will fit together, I have done a lot of Bellawood and its always hit or miss.

Plastic is not used when using asphalt mastic. Yes you would have a BIG mess!

Asphalt impregnated construction felt, laid into wet asphalt mastic, as if you were laying a vinyl floor, only over lap the seams, instead of butting them. Then lay another layer on top of that, just the same and using the mastic, over lapping the bottom seams and then over lapping and not butting those seams the same as you did on the bottom layer. Install your plywood perferably on a 45º to the installation, so seams of the plywood don't land under a row edge of flooring, or panelization might occur.

Poly plastic is for floating floors, that your not going to penetrate with fasteners. Asphalt mastic will disolve some plastics.

I was not talking about floating the 3/8 solid, I don't believe that is recommended. I was talking about floating the 5/8 plywood subfloor and attaching the 3/8 to it either with adhesive or fasteners. You would have an inch of floor, bouncy isn't going to be a problem, unless you fail to do the proper floor prep for substrate flatness specs.

floorguy, thanks a million for that info - I've been reading conflicting stuff around the web (some things i've read say to use mastic to adhere the poly. to the concrete). The method you just described, I'm assuming that's with 2 layers of 15? also, do you put down mastic and apply the tar paper as you go or put down all the mastic and then wait the 2 hours. I'm assuming that one uses a fairly thin layer of mastic as well - is it necessary to use a notched trowel for this application? Also, is it necessary to cut the tar paper into smaller sections or can one just use a "wall to wall" length?

thanks again for all the fantastic advice!

--nm the wait 2 hrs uestion, just saw your note about "wet asphalt mastic"

--ok, another one - is it possible to float just one layer of plywood? I thought one always screwed two layers together for a floating subfloor?

--ok, one more edit. Since I've never put down a moisture barrier like this before I want to make certain that I fully understand the way it is supposed to turn out - are the two layers of tar paper supposed to be..."squishy" or lay flat and firm, e.g., little or no tar squishing out the sides if weight is put on it. Also, would one lay ply as one goes or get the whole place covered with mastic and tar paper and then lay ply after that (strikes me as requiring a fair bit of walking on the mastic/tar paper moisture barrier).

--ok, still thinking - would it be better to float 2 layers of 3/8'' plywood (glued and screwed together) over a 6mil poly moisture barrier or go with the above method of masticing down 2 layers of tar paper and then shoot 3/4'' ply into the slab???

thanks again for all the great advice

thanks for all the help everyone.
One last followup question - I am going to be putting the braz. cherry in the kitchen but i'm currentl unsure of whether or not I should bother putting braz cherry under the stove and dishwasher..? (I also have a pantry/washer dryer closet in the kitchen would you recommend putting cherry in there as well or just leave the linoleum?)

thanks!

CM:

Yes, run the hardwood under the appliances. Not a good idea in the pantry when I see washer mentioned but the choice is yours.

More tips on appliances and hardwood installations...

http://www.hardwoodinstaller.com/hardwo ... start6.htm

Thanks much for the info KD, I was starting to think along the same lines regarding the washer and dryer.

What about this stuff?



http://www.mpglobalproducts.com/insulayment/1intro.html