Hello All! Thanks for providing us a place to ask questions about things we know nothing about!

I plan to install a nail down floor in the near future,but have never installed hardwood before( until recently I had also never installed ceramic tile,but now have three rooms with it)

I understand that I need a plywood sub on my slab, and from checking around and reading found out there are a couple of methods for securing the plywood to the slab. I am not concerned about "THE EASIESTED METHOD" here, I need to know which will be the most secure.

First is the power actuated nailer(which sounds to me to be simple) will I have any trouble getting the nails flush with the top of the plywood?

Second I heard I can use something called a "split drive anchor" which means I have to drill holes first.

So which method will keep my plywood firmly attached to my 14 year old slab that is going to have numerous cracks in it? (know that from putting in the tile)

Thanks again, look forward to getting some great info in the future.


Mike


P.S. Is the power nailer very dangerous to use? The single shot kind.

Here is a URL that will be very helpful to you.


http://www.fcimag.com/CDA/ArticleInformation/coverstory/BNPCoverStoryItem/0,2986,140403,00.html[/url]

You are supposed to have about 1" of nail in the concrete. I used 1/2" ply as my base layer and even with the yellow cartridges, I could not always sink a 1 1/2" nail so I used a 1" nail which coutersinked well. If the nail does not sink all the way, you can always pound it down with a hammer although it probably does not go into the concrete any further - it just deforms which is OK. Run a test before you commit.

Before I did mine I talked to an installer with 30 years experience and he would not do a ply over slab without using 2 layers with staggered seams (glued and screwed). Chances are the PAF's will eventually fail and then your floor will fall apart. In fact, about 5 to 10% of your PAF's will immediately fail whether you realize it or not. Concrete anchor screws are better but it's extremely labor intensive. With the double layer ply method, even if your fasteners fail, your floor retains it's integrity (but don't attach any floor parts directy to the concrete, like transistion strips). Also, you should flatten the slab because especially with 3/4" or thicker ply, the fastners won't be able to deform the ply enough to conform to the dips.

I personally don't see many reasons to justify this type of install. The amount of labor is immense. They now have site finish glue down with 1/4" wear layer. When I did mine they did not have these and I also wanted a border.

You might also consider raising the surrounding floor levels because the thick reducer is not ideal either. Howver, this is a messy and difficult job also, especially at doorways.

Alexh

Thanks for that information. I feel like I will probably pass on the PAF method.

May need to pick your brain again later as the job starts.


Mike

One of my old enemies turned me on to a good fastener.

http://www.smithfast.com/redidrv.htm

The redi-drive is the best design I have seen for mechanically fastening plywood to a slab.

Ripping,kerfing and gluing on 45ing is the way to go for me.

M in M:

Have you considered NOT fastening your floor to the concrete and instead floating the whole thing? I am in middle of whole house floating install of nail-down over two ½” layers of plywood sub-floor that was laid over flattened concrete. Process I'm using is described elsewhere on this board. Feel when walking on just the plywood sub-floor is slightly soft but it is very nice underfoot. Spent a lot of time flattening slab with thinset and a grinder. Nailing down the actual flooring is simple when compared with the all the non-seen stuff under it! But as with any project, preparation is the key to a successful install. With additional ¾” of nail-down over the ply, floor softness is much reduced but not totally eliminated. That's a good thing! No problems with moisture either as the poly forms a pan in each room that is not broken between the wood and slab. Have some old oak engineered that was glued to slab. The softness difference between glue down engineered and nailed down T&G over plywood that has been floated is noticable. But I like the floated better. Plus it is warmer in the winter. Doubt that with weight of a total of 1” of plywood under ¾” of nail-down plus the 10 mil poly and 15# felt that I will have problems with it moving. Elected to not use T moldings but am instead doing it without joints because it looks better. Left 1" space around all walls and jambs just in case something expands or moves slightly but I doubt that will happen.

Floating is an alternative to the glue mess and smell but not even close to being less work. Doubt that any professional installer would even consider this method due to extra labor and costs involved. But for a serious DIYer willing to take the time to do it right, I think it is a good alternative. Something to think about...

VP, I have done 2 such floors like you are doing, only I used rubber cleats on the bottom of the subflooring to raise the subfloor off the moisture barrier a ¼" Little rubber 2 inch by 2 inch pads, I fastened every sq. ft. to the subfloor.
The clients loved it and I was able to do what no one else said could be done, over their wet concrete.

I said - "Doubt that any professional installer would even consider this method due to extra labor and costs involved."

I stand corrected!

Here are two progress pictures from a couple weeks ago showing the subfloor plywood layers and plastic. Would like to have done 2 - 45 degree layers but that is a lot of work! However, am making sure each doorway a has full length of the 45 degree layer going through it to add strength. Actual flooring will be nailed 90 degrees out from top plywood layer:

Nice!

Good thing that exterior door threshold sits high--or at least it does from my view. I see somebody has alot of meticulous trim work to do too--IE rounded corners.



You're right--at least I've never seen the ply cut into 2' x 8'--4' x 4' yes for other reasons.