I'm looking for some objective advice.

Here's the situation: My above-grade condo has 2"-wide oak plank subfloor covered by a 1/2"-1" thick acoustic, aka 'gypcrete', cement underlayment which is wavy and cracked. Two installers who looked at it said engineered wood planks could be floated over it after leveling...BUT, I have doubts. Moisture isn't a problem---it's the expanding and contracting subfloor. Is a floating floor appropriate here or should I stick to carpeting? Am I trying to make a silk purse out of a sow's ear?

I'd float it in a heartbeat.

That is actually the only way I would install wood over that substrate.

Sand as a floor leveler? I've used it before.

It's there but hard to find..

http://www.harris-tarkett.com/PDF_files ... gstrip.pdf

Thanks for your responses. Didn't know about the sand leveling.

Is there a high of risk of failure floating planks over my kind of subfloor/underlayment, or is this fairly straight-forward for a skilled installer? (I'm not going to try this myself)

You know, your situation sounds bizzare. A 2" OAK subfloor? I doubt it. What I think you have is a oak floor someone put a leveling compound on without priming or preping first and the compound is cracking and breaking up because it was not done properly. Perhaps you could do a little investigation by going in a closet and chippng out a small section of the "gypcrtete" and then using a circular saw, cut a section of your "oak subfloor" out and see what is below. Question? Is your condo unit on the second floor? It maybe that someone glued an oak floor down and it made too much noise to the unit below and someone complained and the remedy was to pour that crap you see over the oak floor and then carpet it. If this is the case, the proper way would be to pull all that stuff out till you are down to the true subfloor (it maybe wood or maybe concrete). Then properly prep the subfloor for a floating floor with an acoustical underlayment such as cork. Lots of work but no worries about the shifting sand under your floors.

Gary, yes it is strange. This is in an above grade condo that was converted 30 years ago from apts, which is maybe when they put in the gypcrete. On the subfloor thickness, I meant the wood planks are 3/4" thick (and 2" wide). I scraped away the gypcrete and stuck my finger down the side of the planks to verify this. So to recap, I have what was a once perfectly good 3/4" wood subfloor covered by 3/4"-1" thick gypcrete. I don't know what the wood is on...Joists.... Perhap plywood, too. Anyway, I think I will contact a wood floor inspector to look at it before doing anything and perhaps give some independent advice. The National Wood Floor Assoc. has a listing. I hesitate to tear up the gypcrete.

Also, to answer your question, yes it's third floor.
If I do rip out the gypcrete, do you have any suggestions on what to replace it with that is: 1)flat 2) fire/noise barrier and 3) will isolate eventual floor from shifts in wood subfloor?

I think having an inspection done is a wise choice. We can't see what's going on and have to rely on your description. Some folks use the wrong terminolgy and that confuses the situation. I still think what you have is an old oak floor over a plywood or solid wood subfloor. Never heard of or seen a subfloor in 2" strips. Narrowest I've seen is fir decking/flooring at 3&1/2" wide. They put the gypcrete over it for leveling, sound and fire. But as long as the oak flooring is there, it will continue to expand and contract, causing the gypcrete to crack. If the gypcrete is well bonded and not breaking loose, then theorectically, you should be able to level it with a cementious patching compound and then float a floor over that.

Gypcrete is for noise and fire as stated. It is code.

Apartments around here they bust it all up and lay OSB, not realising that they are breaking code, but what city inspector, comes by when the floor is being replaced?? NONE, NEVER WILL!


ARDEX GS-4, pumped to fill and cap.

Gary, I think your old oak floor analysis is correct. Sorry about the confusing terminology.

Also, I just got off the phone with Rusty, the tech at National Wood Flooring Association. He has 30 years of flooring experience. http://www.woodfloors.org/consumer/ This independent organization may be another good source of information for people posting on this board with questions.

As far as my situation I seem to have three options which I will discuss with the inspector:
1) Rip up gypcrete underlayment and replace with combination cork&plywood that meets fire code&sound specs.
2) Rip up gypcrete and reinstall fire/sound proof light-weight cement (e.g., Ardex stuff).
3) Patch existing gypcrete w/ Ardex.

#1 is $$$ but gives most options and best long-term solution. #2 is not cheap either. I'd basically end up with a new, more stable version of what I have. #3 is cheapest but more risk.

There are lots of gypcrete posts on this board. Must be keeping those cement guys real busy.

dukie

Oh, floorguy, I think you're right about enforcement. There are so many county rules and regs, the code enforcers must be swamped and no way are these civil servants going to loose sleep over 500 sf in a puny condo. Only issue is resale later on down the road, so I want to do it right.

Perry (Floorguy) and I are well aware of the NWFA. We are both members and Perry is a certified inspector.

If your going to patch and cap what you have now, so the floor is flat and stable, use the ARDEX GS-4.

If you bust it all up and start over, use Maxxon

www.maxxon.com

Floorman, I'm beginning to think busting it up may be the only way to go.
I will consult with the inspector, first, though.

My guess is that buckled, warped subfloor strips are making the gypcrete subfloor all wacky. It may even be sagging/humped joists, or worse, building settlement. I'm hoping that if/when I bust the gypcrete, I'll be able to screw down or replace those warped, sqeaky strips, as I can't do much about the joists & settlement.

Maxxon, eh? The pros have to pour that....What about 1/2" cork (for sound) with a fire-rated 1/2" plywood or cement board?

I hope gypcrete doesn't have asbestos in it....