Originally Posted by
Milo Dolezal
I am glad you are planning on water-proofing your shower pan. It tells me you want to do things once and correctly. Lot of people don't. It is definitely a big mistake. Yes, tile and grout itself will prevent direct water from penetrating the base. But it is the Condensation that is produced every time you turn hot water on, that will produce wetness (leak) around shower base area. That's why we water proof shower pans.
No, existing concrete slab will act only as the solid base to build on....
You have 2 ways to proceed:
ONE: PVC LINER SHOWER PAN
1. Build 4 1/2" curb at the entrance to the shower
2. Install proper shower drain. Drain must have 3 holes to allow drainage of condensation aka "weep holes". I recommend Cast Iron Instant Set shower drain.
3. Mix bucket of Mortar Mix. Mix it very dry.
4. Apply this mix around the outer edge, on the outside perimeter of the shower pan edge, about 3/4" high. Use trowel to spread it towards the drain, creating gentle slope.
5. Get on large piece of PVC liner
6. Remove upper part of the drain and put it aside.
7. Lay liner over the entire area of new shower pan and overlap 12" hight onto each wall and over the curb. Don't cut in corners unless you are very familiar with installation. Nicely, and tightly, fold excess PVC in corners and staple to the wall. Same over the curb. If you are experienced in PVC liner installation, you can make cuts. In this case they sell inside / outside corner patches that will glue over cuts. Important: even it is called PVC liner, it takes different glue than the once you would use for PVC pipe. Use ONLY glue that is specifically designed for PVC liners.
8. Put bead of black mastic (like Henry 208) around the bottom part of the drain and around its perimeter. Be generous
9. Reinstall upper part of the drain over the mastic, squeezing it out
10. Install concrete over the plastic. Concrete must slope towards the drain at minimal slope.
11. Install tile
12. Seal the grout, tile
13. Open up drain cover and cut out PVC liner that is covering the drain. Have needle nose pliers ready to grab the cut piece so it doesn't fall inside the drain.
TWO: HOT MOP INSTALLATION
It is basically same procedure except that Hot Asphalt will take place of PVC liner. Hot Moping is usually done by worker specializing in this type of work.
When installing hot mop, they will first install layer of #40 paper over existing floor, than hot mop it. Hot Moper will then install dry mixture of concrete creating slope towards the drain. Then again, they install another layer of #40 paper with hot asphalt over it.
Two layers of concrete are necessary. The first (slab) is your starting base, the second layer is sloped toward the drain to lead condensation to the drain.
Depending where you live, opinions about PVC and / or Hot Mop pans vary. Hot moping is an old, well proven method while PVC liner is relatively recent upgrade. Regardless, both methods are approved by Code and both methods work.
