johnfrwhipple

In trying to find the best "Latex Primer" for my "Kerdi over drywall" installation guide I have come up with a few road blocks. I checked with Schluter and managed to get not a product specifically as a recommendation - but I was told that Mapei and Custom Building Products make latex primers that I could use with Kerdi installations over drywall compound.

I called Mapei and they do not recommend drywall in showers and said they have no product they recommend for a Kerdi installation over drywall. I have heard from multiple people that thin-set, espcially non-modified thins set or dry set mortar does not stick well or at all to drywall compound. The finish mud and taping mud the drywallers use to smooth out a wall.

I also checked with Custom Building Materials and they like Mapei said they advice against using drywall in a shower and can recommend none of their products to install Kerdi over drywall or drywall compound.

So I sent of an email to Schluter asking for an exact product and as yet have not heard back from them.

I decided to test a few of the products myself. I'm a huge fan of Mapei and have been using a lot of their setting materials and waterproofing products of late.




Thursday , 6:00 AM December 29th.



Grani Rapid Liquid "Ad-Mix" as Latex Primer over drywall compound

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I prepared three sample boards with a coating of Grani Rapid Liquid and three more samples of Planicrete AC

Each of these samples boards where made by first applying a thick layer of DryDex over the plexi glass and then a skim coat of Lite Line drywall compound from Synko.



The DryDex when wet or damp turns pink. As it dries it goes white and this is a great product to use when painting to ensure you don't sand a patch to quickly. Here in this expierement it will stay white as long as what ever waterproofing product I use does it's job keeping the water out.

So I think it is best we give the primer a good day to dry.

Tomorrow I'll waterproof each of these samples with a different system. Lets see how all waterproofing products work with drywall and espiecially the Kerdi since it is only Schluter that recommends this process.



Thursday , 6:00 PM December 29th.

12 hours has past and my six samples are at two separate stages. The samples with the Planicrete AC "Ad-mix" looks good to go. The surface is not tacky and the "Ad-mix" has bonded very well to the drywall compound (Synko - Lite Line).



Grani Rapid Liquid "Ad-Mix" after 12 hours over drywall compound.

The three samples I prepare with the Grani Rapid "Ad-mix" are still tacky. I'll let all six set up over night and start waterproofing in the morning.

FRIDAY MORNING



Before applying the Grani Rapid Liquid Ad-mix I lightly sanded the surface and removed the little bit of dust generated by this step. The number one reason for tile failure is "bond breakers" and dust is one of the biggest foes you have building your new dream shower. Did you catch the biggest mistake I made in applying the Aquadefence? Not the lack of a film guage but the actual installation process with the brush.

Watch the next video with me installing Red Guard. With this second video I show a better application approach.






The "Mad Lab"


Stay tuned...