Installing kerdi mat is not as easy as they make it look on the Schluter DVD. I'm installing it over denshield...the last time I used drywall but it seemed like the thinset lost its elasticity to the absorptive surface. I took Harrys advice about using mapai ultra contact over heating cables on a job and liked its consistancy. Would that be a good product to use for this application? Thanks for weighing in.

Hate to tell you sahara but you wasted your money by putting up DensShield. It already has a waterproof barrier. The correct choice should have been just regular drywall.
Kerdi actually bonds better to regular drywall.

I take it your using a non modified thinset to bond to the DensShield.
Seeing as how your using Mapei products, you should be using Mapei Kerabond for the Kerdi installation and the same thinset for the tile installation. Grey or white will depend on the type of tile, stone or grout used.

Thanks Randall. Lucky for me I was waiting for a reply before purchasing the denshield. So back to drywall. Will the Kerabond still be the morter of choice? Thanks..don't know what I'd do without this site, Susan.

Yes, use the Kerabond.

Green board is what I'd recommend under kerdi, because the paper on it holds up better to the moisture from the thinset. Either way the drywall paper sucks the water out of the thinset very quickly. Give the wall a wipe with a wet sponge just before you start and mix the thinset pretty runny to give yourself more working time.

You're wrong Pete. Although greenboard will work just fine, regular wallboard is better, and that is what Schluter recommends.

Regular wallboard is better because it is stiffer than gb. The thinset bonds and cures fine over either, I have never needed to moisten it, and no directions I've seen makes any mention of such. The only board that requires hydrating is Hardie.

You have to mix your thinset a little thinner than normal, if you know what that is. Kerabond is one of many that will meet specs for Kerdi. If you had a Hydroment brand source, I'd recommend Ditra Set, which is licensed by Schluter for Ditra and Kerdi installations.

Jaz

I've been wrong before, and could well be this time too. However I don't get how you figure that regular drywall is better than greenboard. Greenboard is essentially drywall with a face paper that holds up better in moist conditions and it's exactly as rigid as drywall. the only advantage of drywall is that it's cheaper. I have never found anything written by Schluter that recommends one over the other and I think that I've read everything that Schluter has written on the subject.

I don't want to start an argument, I am always looking for better ways of doing things. As for dampening the paper, it's worked for me, but I guess if you're fast enough it's not necessary.

Pete,

It's a common assumption many make, no problem. However, regular wallboard IS stiffer than greenboard. (You can easily test it yourself). As a matter of fact when used on ceilings, gb should be installed on joists that are 12" o.c. as apposed to the normal 24" for the regular cheaper stuff.

With a Kerdi installation it doesn't matter whether the substrate is waterproof, water resistant or as with gb moisture resistant. Kerdi is waterproof and even better is an effective vapor barrier. I'm not sure where to find the regular recommendation in todays instructions, but I'm sure it's in there someplace. At least I know it was in the older publications.

Jaz