I've been lurking for some time in these forums, and finally decided to bite the bullet and join! I've got a question that I can't seem to find the answer to. Actually, I have several questions. Here's my situation:

I have added a second story to a 1950's ranch (took off the roof and built up), and the original 1st floor comprises a subfloor made of 1x12's on the diagonal, with 5/8" plywood over that. So, the subfloor is about 1 3/8" thick. I am planning on putting 11/16" x 3.5" solid maple on top of this, as well as over some connecting areas that have a new OSB subfloor (3/4").

Questions:

1. Will a standard 3/4" flooring nailer/stapler work for this? I've read some decent reviews on the Harbor Freight flooring nailer/stapler, so long as quality nails/staples are used. I just need to make sure, since the flooring is only 11/16" (17.5mm) thick and not a full 3/4", that I won't have a problem using the tool.

2. Considering most of the subfloor is over 50 years old, is there any reason to avoid either cleat nails or staples? Also, I forgot to mention that the plywood did get wet while the roof was off, so there's a little bit of crackling from delamination of the top layer, but it is structurally sound. (I actually want to use the fastening of the hardwood to further push any crackling layers down.)

3. Between the 1x12's and the 5/8" plywood, there is original felt paper that was designed as a moisture barrier. Should I put another layer of felt paper down under the new hardwood, or will this cause another problem with keeping moisture between the 2 felt/tar paper layers? If I shouldn't put down the additional felt paper / resin paper, is it proper to just put the new hardwood over the existing bare subfloor, or does there need to be a layer of "something" between the two?

Thanks so much to all of you who have already guided me through this process without knowing!

1) You may need to adjust the shoe of the nailer a bit. But a 3/4" T&G flooring nailer is what you need. I've heard positive reports about the Harbor Freight nailing machine.
2) Cleats or staples are what you want to use. The manufacturer most likely recommends 2" legs on the fasteners and I would agree with that, especially since you have a thick subfloor.
3) Yes, you should install a layer of 15 lb. asphalt saturated felt paper under your new flooring. It will not cause any problems. The asphalt felt is NOT a moisture barrier. GEEZ, how many times do we need to keep saying this? It is a vapor diffuser, among other things. Underneath your home must be dry and covered with a 6 to 8 mil polyethylene vapor retarder. Notice I didn't say moisture barrier (such a thing doesn't really exist ). If you have a full basement, you don't need the vapor retarder but the basement cannot be damp and musty either.

Follow the directions that come with the flooring.

Thanks, Gary. Sorry I said "moisture barrier" -- I meant to type "vapor barrier", even if it's not a true "barrier", but more of a diffuser. Anyhow, in regards to my second question, sorry for the confusion, but I guess I need to clarify. I wasn't inquiring as to whether I should use "cleats or staples" vs. some other type of fastener, but rather, if there is a reason to choose one of cleats or staples, considering the subfloor is 50 year-old wood that is not as resilient as new wood. In other words, will cleats have tendency to crack the dry wood subfloor more than staples, or vice versa, or does one have more holding power over the other in such a circumstance? I know that the nails vs. cleats debate has been going on for a long time now, but I'm not sure how it relates to going into a subfloor consisting of old plywood over old 3/4 solid planks.

By the way, the diagonal 1x12's I spoke about are actually 1x6's. I was thinking about the exterior wall sheathing when I was typing (the sheathing is 1x12's). Oh well - I think you got the picture anyways.

My main concern is making sure that the fastening means will grip well in the subfloor, so that the new hardwood holds tightly to the plywood to hold down the flooring and to eliminate the crackle cause by the delamination of the top layer of the plywood. The roofing felt may help to deaden the crackle, also, so that's another reason to use it, as opposed to resin paper. Like I said before, the plywood is structurally sound, but in a few areas, the top layer has delaminated slightly. It's flat & level everywhere (even in delaminated spots), but you do hear some crackles when walked upon, because the old glue used to hold the plys together probably wasn't water resistant. I've screwed some of those areas down to eliminate the crackle, but I was hoping that nailing/stapling the hardwood down would accomplish the same thing, and eliminate the extra screwing (and potential hitting of the screws when nailing/stapling the hardwood).

This brings about another question. The top layer of plywood was once used as the "finish floor" when the house was first built, and there are no gaps between the sheets. Perhaps I should also run a circular saw along the seam between the sheets to make a slight expansion gap to avoid future squeaks/crackling? Any thoughts on this?

Thanks again.

IMO, there are no advantages or disadvantages to either staples or cleats in your situation. Some say staples tend to split tongues easier than cleats and that may be true in very hard floors. I have used both and do not believe one is better than the other EXCEPT when installing over OSB subfloors. Then, staples are what I prefer.

Not a bad idea and would only help. How thick is the plywood over your 1 x 6 subfloor?

Gary -- The plywood overlying the 1x6 planks is about 5/8", and it is ring-nailed to the planks and joists, but butted together with no gap. I also have 3/4" OSB in a front area where I added additional SF to the 1st floor.

Also, the maple flooring is 3 1/2" wide -- will this width of the plank cause any greater concern with regards to any of the issues we discussed?

Thanks!

Make sure the plywood is secure with no squeaks or loose areas. Refasten as needed.

No. Maple can split easier than oak due to it's hardness and brittleness. Follow NOFMA's installation guidelines for a 3/4" solid over wood subfloors.

http://www.nofma.org/Portals/0/Publicat ... Floors.pdf