Hello, I'm going to start a drain pan (my first) and am looking for some guidance. My subfloor should be fine, 5/8" ply over 3/4" ply over 11 7/8" WI joists 16" on center. These are the steps I want to take but not sure if I'm correct.
1) unmodified thinset
2) mud (slope 1/4" per foot) 1" thick at drain
3) unmodified thinset
4) kerdi
5) thinset
6) tile

Is this order correct? Did I miss anything?

What is the best recipe for the mud, I've seen so many. 5 parts sand 1 part portland? Is there a premix I should use?

One last question. I was thinking about using redguard instead of kerdi or maybe both for extra protection, any reason not to?

Thanks
Gary

The steps you have outlined are for building a pan on a concrete floor. On plywood you want: poly, diamond lath, mud, thinset,kerdi,thinset,tile. I use premixed sand mix or topping mix concrete and have always found it to be fine. Some guys like to add a bit of sand to the premix because it tends to be more like 4 parts sand. Use either Kerdi or 3 coats of redgard, but not both. Redgard avoids the corner buildup issues that you can get with kerdi, but its not quite as tough. You can also use Kerdi shower pan and redgard on the walls.

Thanks for the reply Pete I didn't realize that was for concrete floors only. I do have a problem with it. Over my subfloor I have radiant floor heating and then 3/8" plywood over that so I won't be able to safely staple the lathe down to the 3/8" ply unless I use 5/16" staples which I don't see holding anything.
Are 5/16" staples good enough?
Is stapling the lathe to the surrounding walls and the curb good enough?


Thanks again
Gary

the lath does not need to be stapled down at all. It does the same thing that rebar does for concrete, which is make it stronger in tension.
I have to say, this is the first time I have heard of radiant heat being covered by plywood. Is this a manufacturer recommended process?

Thanks for the info pete, I thought it had to be secured.

Yes it is Ok by the manufacturer to put plywood over the radiant. I have Rehau Panel (6" centers) and they recommend 1/4" ply but I went one step thicker with 3/8" ply and I had a heatloss calc completed by a radiant engineer (not sure on that title) and there were no objections for the thicker ply over the radiant. I am putting carpet (yes carpet) in the areas adjacent to this pan that I am working on and that's the real reason for the ply. In fact this pan is in my mechanical room on the 2nd floor adjacent to the hallway. All of my plumbing for the 2nd floor heat will be over this pan that I am going to build including the manifolds and a 20 gallon superstor tank. I also have my second floor domestic plumbing distribution manifolds over this pan so although this pan shouldn't get much use there is the potential of some serious water.

Thanks again Pete
Gary

Ok, now I have the tar paper, lathe and Kerdi drain in (no access from below) and have a question on the slope before I begin. I have a rectangle drain pan approximately 23" x 58" and the drain is close but not on center. If the drain flange is 1" off the floor I plan to go 1 5/8" on the long side (29" from drain center) which is approximately 1/4" per foot slope. Now I only have approximately 11 1/2" from the short side to the drain center. Do I bring up the mortar to 1 5/8" like the long side which will be over 3/4" slope per foot or do I bring it down to 1 1/4" to maintain 1/4" slope all the way around.

Thanks
Gary

Keep the pan level all the way around the perimeter.You set that height at 1/4" per foot calculated from the the drain to the furthest wall corner.

Thanks RC.

Gary