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Shazza 12-03-2009 06:53 PM

Bamboo Flooring Installation - subfloor question
I am planning to install bamboo in my living room (5/8" x 3-3/4" x 3') over approximately 380 square feet.

After pulling up the old carpet I discovered a layer of "concrete" over my subfloor. After some internet research I am guessing this is gypcrete or something similar.

I live in an upstairs condo so I assume it was used for sound and fire protection (although I think it fails miserably as a soundproofing material). My HOA does allow hardwood floor installation so that is not an issue.

I also believe the stuff over the subfloor may be a code requirement so I do not want to remove it.

In an effort to be a good neighbor I would like to put cork underlayment under the bamboo. The bamboo is approved for glue down and staple down installation only (not floating).

I have several questions:

1. Should I assume this material is gypcrete? What else could it be? How do I determine that it is gypcrete?
2. Assuming its gypcrete, how should I repair scratches/dents etc?
3. Assuming I have to keep the gypcrete due to code how can I install the cork and bamboo?

I know the ideal option is to put plywood on top of the gypcrete, but that will create too much height and will make transitions at my sliding door and fireplace look awful. I will also have door height problems at four locations.

I know that my best bet may be to get someone to install it for me, but I would like to explore all other options first.

Any and all advice is appreciated.

msv 12-03-2009 11:18 PM

bamboo glue-down
IMO, you should patch any cracks you have in the slab, glue the cork down(full trowel spred), let the glue cure, and then glue the flooring on the cork.
i've done plenty of condos with this method. It will cost you for the cork and double the glue, but it will be more duralble than nail-down. Never heard of floating solid bamboo, honestly. nailing 5/8" wood, especially bamboo(softer wood) will eventualy produce squeaking.
You can also skip the cork and glue down on the current subfloor, as long as it's a level and sound surface.

Shazza 12-28-2009 03:53 PM

MSV thank you for your feedback.

We have determined that we can only go with glue down even though we didnt really want to.

As an update for anyone with a similar problem here is what we have done so far:

Ripped up vinyl in the kitchen (put down in 1989 so no concerns of asbestos) and scraped all of the adhesive off the gypcrete. What a PAIN this was (and I mean that literally). We bought a couple of 4" wall scrapers and painstakingly removed old old thick adhesive off about 100 square feet of floor. The gypsum concrete in this area is not in great condition as some of the upper part of it came off with the adhesive.

Removed carpet from another 300 sq ft area and removed carpet adhesive (again with the scrapers). Went through a lot of blades with these two areas but i am really confident that we have got every bit of adhesive off the floor.

Next steps (next weekend) is to prime/seal the gypcrete with Mapei Primer L (probably 2 coats) then apply Mapei Planitex SL (gypsum based self levelling compound) to even out the surface of the floor. There is one area where there is a 1/4" dip that we have to even out and there are some areas that have been damaged by screws so we plan to repair all those and apply a skim coat over the whole 400 square feet. Planitex SL can be applied from featheredge to 1/4".

We then have to wait for the SL to cure and dry (its touch dry in 3 hours and hard in 24 but we need to make sure the moisture levels are appropriate before the next step).

The following weekend we plan to seal the Planitex SL with the Primer L and then put down the cork underlayment. From everything I have researched I believe its best to use urethane adhesive for BOTH the cork and the bamboo even though this adds quite a bit of expensive. I have read that while you can use a latex based adhesive to glue down the cork (cheaper) it is possible that the bond wont be strong enough once the urethane adhesive is used to glue the bamboo to the cork and may pull the cork from the floor. So we will use urethane adhesive (probably Bostik's Best) to glue down the cork and the bamboo.

I think we will probably wait until the following weekend after gluing the cork before starting on the bamboo.

So we still have about four weekends of work ahead of us but I am confident that we have chose the best process for the job (apart from removing the gypsum concrete underlayment which would probably have been best but not an option available to us).

Any thoughts or comments about our proposed process? Any major flaws in it (apart from the unreliability of gypcrete underlayments of course :()?

rusty baker 12-28-2009 04:33 PM

"Ripped up vinyl in the kitchen (put down in 1989 so no concerns of asbestos" Actually vinyl installed in 1989 could have asbestos.Manufacture was phased out from '89 to '91 with Distributor sales another two years and retail sales two or three more.

JazMan 12-28-2009 10:24 PM

When I first started reading I was thinking of Bostik products. Then you mentioned Mapei, and I'm OK with them too. But you then went back to Bostik for another product to be used with Mapei. I'd rather see you use products from one manufacturer only. I believe they both have what you need, no? I'm not a hardwood guy, (although I've done dozens of installs), but I've heard some negative comments about cork as a sound reducer. Have you considered other options? Sheet membrane maybe?


IceT 03-19-2011 01:34 PM

what glue did you use? I like the type that is sticky when you put it down.

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