Hello all,

My arch. gave the ok for putting 3/4 hw on slab. 520sq. 60% of the slab is new. 40% 45 yrs old. That 40% has one wall with a minority portion below grade. on a close bedrock ridge. House is about 40' feet deep (now), ridge about 50'. No moisture issues but the old (asbestos(?hmmm)/linoleum) tiles do show evidence of _something_ from over the years.

My concerns are:
1) Should the old tiles come off no matter what? Or can I leave them if
they are, say, in a levelable hollow?

2)The old slab is not terribly well laid. Ok, hollows I can handle but what about humps? What do I do rent a concrete grinder and generate some dust?

3) from reading other posts it seems there can be two layers of "wood" below the finish wood. Is that accurate? I was going to use a single course of either 1/2" or 3/4" t&g plywood sandwiched inbetween two 6mil poly sheets. Good? Or is another layer of would required. Would Aquabar or somesuch be better be better than poly? Seems poly has a perm of nil...

4) Couldn't find this easily in any other post but given there are no joists how does one secure the sub-floor/plywood to the concrete? concrete nail gun? Flat-head tapcons? (do they make those? Nice idea if they don't. Now that would be tight & time-consuming yes)

5) Should my hardwood cleats penetrate the concrete? For 3/4" hw and 3/4 cdx what length should they be?

thanks to all the posters and especially the responders.
Bryan

1. Remove them (for various reasons)
2.Fill in valleys with floor patch, grind high spots (several tools will work, from a 4" grinder to a large stand buffer with a grinding attachment)
3.Ok i think you got your info mix up and you should check out the NWFA website. It sound like your going to do a "nail" down as opposed to glue down. You only need one layer of 3/4" or thicker fastened down with tap-cons, powder-actuated fasteners, etc., but you'll need some sort of vapor barrier before that (MVP, cold-cut mastic [yuck], or one of many ant-fracture membranes available. I'm not sure about Aquabar, but if it's a anti-fracture membrane it will probably work. Once you have the vapor barrier down first, then you've fastened the plywood substrate, you can nail or staple your flooring with 11/2 inch fasteners.
4. Yes. As briefly described earlier. All of those should work. Countersink your tapcons. I use PL400 or some type of adhesive as well.
5. No. one and a half inch.

Sorry for the hurried responses, did what I could in the time I had.

Search the website more. These topics have thoroughly been described in earlier posts.

Someone else will have more time and give you a more detailed rundown, but this should get your research started.

Good Luck.

Thanks for taking the time and the clarification S,

I have continued perusing the copious amount of posts here and continue
to fill in the gaps as you said. 'scuse the pun...