Greetings,
I have been perusing this board for three straight days after finding it last week. Tons of great info here!

My apologies for making my first post a really long one...

I'm about to start a large DIY install of 9/16 engineered hardwood, 5" wide planks of random length. It's got a distressed maple wear layer (not a brand sold on this HWI.com). We'd like to install the wood diagonally. The first phase will be a glue down install on a concrete slab (post-tension, on grade). We'll be using Bostik BST urethane adhesive, per the flooring mfg recommendations. It's approximately 1200 square feet of concrete that we'll be covering in this phase.

Right now my questions focus on subfloor prepartion. The slab is pretty level but there are some spots we'll need to flatten out. Someone suggested RapidSet floor leveler - is this decent stuff to use? What else would you recommend?

Once the floor is flat, how clean does it need to be? This is a trac home and the drywall & paint trades were none too careful with their slop. In fact, the interior doors were painted (sprayed) on the concrete, so there are large areas of concrete completely covered in latex paint. Will all the latex need to be removed, or is some paint acceptable?

Next, there was vinyl flooring installed in the kitchen. We've ripped out the vinyl and made a valiant attempt at cleaning the adhesive (water, a wire brush, and sweat). I believe we got 95% of it, but there is still some glue around the edges. Is it critical to clean EVERY last bit of vinyl adhesive from the slab?

Finally, the BST product info says to "remove cutback adhesive residue by sandblasting, shotblasting or scarifying" if there are moisture concerns (product info sheet: http://tinyurl.com/oqcvn). A couple of terms I don't understand in that quote: "cutback adhesive"? "scarifying"? I'm not positive if I even need to worry about water - we did a moisture test using plastic taped down to the slab. After three days there was no condensation or color change in the area tested. The slab was poured over a year ago and sat un-enclosed for a good part of the dry AZ summer last year, so the concrete has had a good chance to dry out.

OK, that's it for now. I look forward to hearing your responses!

Joe

Latex paint has to go, or be scraped to a residue, where what is left is in the pores of the concrete.

Cutback adhesive, was used up to the 70's. It is black and a real bond breaker, for all flooring.

Before products for encapsulating the residue in the pores, came to the market, mechanical removal was required by, sandblasting, shotblasting or scarifying.

After you get it down to a residue and you grind your high spots, then screed your low spots, skimcoat the entrire floor with ARDEX SD-F or Mapei Ultra skincoat.

Perry,

I have yet to skim coat a slab as you describe and have a couple of questions about doing this. First, in the past, I'd try to get the slab as clean as possible by razor scraping and wetting the slab and scrubbing. Then I'd vacuum everything up with a wet-dry shop vac and wait till the water evaporated enough, usually overnight. This has been fairly successful so far but a major job. Sometimes, I'd use my buffer and sand/abrade the slab but you can imagine the dust that creates. So I'm always looking for a better way. My questions are:
1) How clean do you need to get the slab if you are going to encapsulate it with Ardex?
2) Does the skim coat adhere to the contaminents better than the adhesive?
I'm curious about this. If I need to get all the paint and crud off the concrete to get the skim coat to adhere, wouldn't the adhesive adhere just as well? I'm just asking because I don't know the answer to this. And if the Ardex skim coat adheres better than the adhesive, why and how?
3) How thick does the skim coat need to be? As thin as possible, like trowel filling a unfinished wood floor? Or ?

Thanks!

Thx Floorguy and Gary for your responses. I was wondering about the adhesion of the skimcoat vs. the adhesive as well. I guess it couldn't hurt to do that step, except for the part where I have to pay for the product...

I'm really looking forward to getting started on this project - the walls are almost all painted so we should be good to go pretty soon, maybe even as early as this weekend!

The thick coats of paint. If you ever dry scrape, the thick paint, where they painted doors in the middle of the room and along the the walls where they painted the baseboards, notice how it comes up clean without much adhesion to the concrete. Then notice how a thin misting of paint leaves some in the pores?

Glue manufacturers clearly state not to go over it. Ardex and Mapei market that it will encapsulate the residue, the adhesive doesn't like. Like gluing over glue, with any floorcovering. That is a known bond breaker.

I skimcoat to fill in those little low spots too, as my flat float trowel is almost 2 feet.