Kerdi shower base installation

[Zoltan]

I'm helping a friend install and Kerdi shower base tomorrow and I had a couple of questions come up after reading the Schluter handbook:

- How soon after installing the base on the subfloor using unmodified thinset can we put weight on it and continue the installation?

- When installing the Kerdi on the shower base, how do you handle the base's slope? Won't the slope cause folds in the Kerdi by the drain?

- We're using a PVC Kerdi Drain hooking up to a PVC p-trap. Is it as easy as cutting a piece of PVC the right length to connect the drain to the trap, and then cementing it in place while using the center of the shower base as a spacer and using unmodified thinset between the base spacer, subfloor, and drain?

[Richard Tunison]

You have to let the thinset dry before working over the pan. I'd give it 24hrs.

The slope will not cause folds or wrinkles.

Yes, the drain install is pretty simple. You have the right thoughts on how it's done.

[Richard Tunison]

Please review page 22 for the proper installation of the base when the drain can be attached after the base is set.

http://www.schluter.com/media/shower...v=201401311549

[jadnashua]

FWIW, there is NO reason to wait to install the Kerdi on the top of the foam shower pan...they say that in the manual, and they said that at the Schluter class I just finished this week. Now, if you are doing a mudbed, disregard - wait at least overnight before you do anything to it!

If it is foam, you DO want to protect the top of the pan with something while you may be kneeling on it to do the walls, or other stuff. Do slowly walk all around it to embed it into the thinset on the floor. If you get some depressions in it accidentally, it's best to fill them in and let them get solid before you install the Kerdi to eliminate any birdbaths the depressions will cause. Once the pan is covered with Kerdi and the thinset is set, you still want to cover it to prevent getting it all dirty or poking a hole in it.

In reality, you can cover the walls with Kerdi, then install the pan after, that can help to keep it from getting dinged or dirty in the process. Use the box it came with or a sheet of ply or maybe a hunk of drywall to protect it while working on the walls.

IOW, except that you need to wait 24-hours after your pan is covered with Kerdi to flood test, you can continue with things, and could even tile the walls down to about the top of the curb (leaving the last row out so you can test the pan with a flood test) immediately after installation and not have any problems.

Your biggest thing is mixing the premium dryset properly so the thinset is fluid enough to embed the fleece properly. If you have a good mix, it will give you 100% coverage without having to press it in very hard. Remember to wipe the walls down with a wet sponge (and if cbu, do it a couple of times) before you spread the thinset. AND, it is IMPORTANT to peel back a section of Kerdi to check for proper coverage - it should show that the fleece is fully covered and the wall is as well. If not, you need to remove it, wash it off, and probably make the thinset a little thinner. The thinset should be about the consistency of mayonnaise - smooth, and still be able to hold a notch when you spread it out. Remember to use the flat side of the trowel to fully embed a layer of thinset onto the surface, then add more to comb it out. If you're using the proper sized trowel, you'll get a little squeeze out when you embed the membrane, but not a huge amount. A drywall taping knife works well to embed the membrane. It can help to round over the outer edges so you don't catch them on the membrane...a file makes quick work of that.

Remember, any seams must overlap at least 2" and that there's no benefit to installing things like shingles...it doesn't matter.

[Houston Remodeler]

I like to put the kerdi down at the end of the work day so it has time for the thinset underneath to cure overnight.

WHile you can work over fresh kerdi, you'll get footprints in the thinset which can cause headaches when setting the floor tiles. BTDT exactly one time.

[jadnashua]

FWIW, you don't even need to put the base down, Kerdi the walls, and tile them except for that lower row or so - THEN install and cover the pan in, band it to the walls, let it sit 24-hours, flood test, then continue...IOW, you do not have to even stand on the pan while you are doing other things, and do the pan near the end of your day.

You will put depressions in the pan if you weigh much of anything and you kneel on it unless you use a kneeling pad prior to the membrane and thinset curing. You do want to avoid that. Once the thinset cures, and before the tile is installed, it's best to use something like a piece of ply or drywall to kneel on if you must. Once it is tiled, and that has cured, unless you're 300# and dancing on stiletto heels, it'll be fine.