View Full Version : Under Shower Vapor Barrier
10-09-2009, 12:37 PM
I am building a sauna in my basement where currently the concrete floor has a drain but is not sloped (was set up for a tube). My plan was to roughen up the concrete, build angled screeding jigs (slope to drain 1.5%) and fill the floor space with concrete, mag trowel and call it good. Once dry, I will tile the floor and hopefully the water will move to the drain. I've heard from a few people that I should put a vapor barrier or bladder under the new concrete should water somehow get below the tile and conrete. This adds a whole nother dimension to an already somewhat complicated project and I question the necessity. This will get used 6 months out of the year maybe 2-4 times a week. Can i just seal the new concrete prior to grouting and call it good. Please help. I promised my wife we'd be sweating by Christmas.:eek:
10-09-2009, 01:06 PM
The normal means of doing iths is not to use concrete, but a sand mix (5:1 sand to portland cement). This is sort of like wet beach sand, the cement holds it together. Then a liner, then another layer, and then your tile or other finished layer. Tile is not waterproof, and moisture will migrate underneath. This can rot your stud walls, and give grief. A sauna is sort of like a steam shower, and waterproofing all over is critical to keeping mold from destroying things.
I may be missing something. Check out www.johnbridge.com (http://www.johnbridge.com) for tiling help on your sauna.
10-11-2009, 05:22 AM
Thanks for the reply Jim. What could my min. thicknessess need to be on the two layers of sand/cement?
DON'T put a "proper membrane", AND shower drain fitting, under the shower floor and be prepared for leaks into the adjacent room as soon as the grout lines start to crack.
10-11-2009, 04:13 PM
The bottom layer (pre-slope) since it is on concrete, can taper from near zero to the walls at a slope of 1/4" per foot, so that thickness will depend on the size. Then the liner is installed, then a second layer parallel to the first (therefore the same thickness all over since the first layer is sloped) normally needs to be about 1" thick to have enough strength to hold together.
An advantage to using Kerdi, is that you only need one layer, then you install the Kerdi, then the tile.
The drain you need differs between the two systems and the Kerdi drain is more expensive. You need a clamping drain to use a liner, and you need the Kerdi drain that will allow the membrane to stick to it (no clamp) when using that system.
If the size of your shower is close to that of one of Schluter's premade pans, you could use that. They're a high density foam, and can be cut to size, but work best if you can do that evenly all around (or use it whole). This will keep the outer edge the same height...if you cut more from one side than the other, the bottom edge of the tile won't be the same all around.
View their videos on the www.schluter.com (http://www.schluter.com) website. And, check out www.johnbridge.com (http://www.johnbridge.com) for tiling help. A sauna/steam shower has a lot of special needs over a standard shower or you'll have it fail quickly. Water vapor pressure in a sauna/steam shower is in a totally different league than a typical shower, and needs to be taken into account. The TCNA is the basis for most codes, and has more than one approved build method details shown in their handbook...you don't want to shortcut one of those approved methods. You must have a liner.
10-12-2009, 08:14 AM
kerdi now has an adapter so you can convert a weep hole style drain to the Kerdi drain. You apply kerdi on all surfaces (floor, walls, ceiling) and tile over it, then your good to go.