Shower Pan, Slab, and Cultured Marble

My house has a concrete slab floor and the shower drain sticks up about 3/8" above the level of the slab. In addition I am planning to have a cultured marble shower installed and I have a couple of questions:

1. The cultured marble shower dealer says just put the PVC membrane directly on the slab floor. They also said the bottom of their pan is flat and the top is sloped. This doesn't sound right to me since I would have a "pool" for any water that leaks past the drain to collect. It seems to me I need a concrete base at the level of the top of the drain and then put the membrane on top of this. Who is correct?

2. Assuming I am correct on # 1 above, what type of concrete should I use (e.g. floor leveler, portland cement, etc.)? Also do I need any additives in the concrete?

3. Also assuming I am correct do I need a slope to the drain and if so is 1/4" per foot OK or should it be something else?

4. I have purchased a "perfect curb"... kind of a wire mesh that sticks out 1/2" above the curb and on the sides. Do I just use mortar mix on this?

Thanks,

Mike

Does the pan have the curb cast as part of it? The whole pan up to the top of the curb needs to be waterproof. Typically, they aren't installed with a liner.

If the pan does not have the curb as part of it, I don't know how you'd end up with a waterproof structure.

In a conventional shower, the liner would go over the curb and be fastened outside with the liner also going up the inside walls at least a few inches above the curb.

The junction betwen a manufactured pan and an add-on curb would seem to be problematic in trying to keep things waterproof and not get water accumulating underneath.

A liner should NEVER be installed flat on the floor, regardless of the type of pan construction. The top waterproof layer (and in a tiled pan, the tile is not considered waterproof) needs to slope to the drain. In your case, the cultured marble is waterproof, then to put another waterproof layer underneath it is asking for troubles. The only way to make the bottom liner waterproof is to use a clamping drain, and then there'd be no way to properly seal the marble pan to the drain, so water would accumulate underneath. IMHO, ugly situation!

Have you considered building your own pan? It's not as hard as you think. An alternative to that would be Wedi or Kerdi. Then tile it. Epoxy grout is very resistent to mold and cleans easily. Check out www.johnbridge.com 's Tile Your World website for help on this as well...lots of ideas and lots of expert tilers there.

The cultured marble pan doesn't have a curb. It's basically flat on the bottom, and tapered on top so they are assuming you will use a membrane to prevent leaks.

Mike

Sounds like a disaster waiting to happen. Run this by the folks over at www.johnbridge.com. I don't see how you would ever keep moisture from getting under the pan or how you would seal the drain. What do the manufacturer's instructions say? Do they have a link so people could look at them?