ECN Forum Forums General Topics of the Trade General Discussion Area Gypcrete

Anyone ever work with Gypcrete? A customer wants a floorbox installed in some existing Gypcrete. Will it cut easily with a dry diamond blade? Anything I should know first, besides if there is a hydronic system in it?

are you going to need some sort of fire stop ?

Gypcrete cuts the same as any other cement product; a little harder, a little dustier, no aggregate or rebar to speak of.

It's usually poured in a thin layer (less than 2") over normal concrete.

The most common use is to obtain a particularly flat, or specifically sloped, surface. It's often used to 'correct' a bad pour ... or, as you suggested, for embedding heating tubes.

The other frequent use of gypcrete is to provide a fire retardant barrier to wood constructed multifamily dwellings between units constructed one above the other. I agree about it is harder to drill than standard concrete. The fire stopping question by another poster is something to consider if this is the type of install you are encountering.

There are already floor boxes installed at construction. I assume they poured the gypcrete around them. One of them is not where they want it. I thought if I patched with a gypsum based product, it would serve the firestopping purpose.

....... blank that one up and install a new box where they want it.

explain that you don't really want a soft spot in their concrete floor, or you may end up with another problem later

thanks thats a good idea. Funny thing I spent a lot of time searching for Gypcrete repair and cutting info on the web and came up empty handed. Also, no one I have asked about it even knows what it is, including two general contractors and half a dozen Helpful Hardware Guys. It is being poured here on the big condos.

Here's an update on the Gypcrete. It was barely 1" thick and poured over a 3/4" chipboard subfloor supported by gluelams every 12 inches. It was extremely easy to cut, I cut it with my recessed can hole saw. You could carve it out with a screwdriver if you wanted. I was able to remove the Romex from the unwanted box and fish it to the new box, which I supported by fastening a 2x4 platform between 2 gluelams. First I fastened two pieces flat against the gluelams then placed the platform across them.

I cut the old box off flush, then filled it with a gypsum based concrete patch, patched my holes and filled in around the box. Job done and fire rating intact.

It was way easier than trenching a slab.

Good , glad it worked out for you