I am doing my first kerdi shower. I have put in a packed mud deck (about 38" x 60") which slopes to a linear drain along one short wall. After putting down the kerdi on top of the mud deck, I would like to place concrete over the kerdi and then seed it/trowel in black stones to give the floor a pebble tile look. I have dozens of boxes of smooth, black stones that vary in size from peach pit size to maybe 2 or 3 times that large.
My question is, what thickness should I make this concrete floor and what would be a good mix? I was thinking about 1.5" to 2" thick? 1-3 portland -sand with pea gravel aggregate?
I am also considering about putting a 1/4" expansion gap around the perimeter which the wall tiles would cover (and it would be caulked) and putting some plastic stucco lath into the bottom third of the concrete for reinforcement.
Concrete isn't very porous. You want a porous material above your waterproof layer.
On the other hand, deck mud is not strong enough to hold in your pebbles. I think the way to go would be the traditional way: Use thinset to adhere your pebbles directly to the waterproof layer, then grout the pebbles.
Hopefully a pro will weigh in to confirm or rebuff me for giving bad advice.
Success with thinset will be dependent on the size and shape of the stones. If the the shape of them results in little contact with the floor, they won't stick. Are they sufficiently flat on any part to allow for good contact with the floor?
Of course, once grouted they would be held in place fairly well, but they still need some contact with the floor.
My idea is to put down a thin layer of concrete (1.5"-2") on the kerdi and seed the stones into the surface- you trowel them in flush just below the cream and then wash/brush off the cream to expose them. It's a common technique used to get an exposed aggregate look. The stones are all different sized so there is no way to thin set them to the kerdi and get an even surface.
You'll have to pitch the floor better than 1/4 per foot to get those rocks to drain properly. If the floor isn't pitched enough you may end up with pudding. If you're looking to get a flat pebble floor I'd use flat rocks. With those rocks that your describing I feel it's a better look letting them do their thing. They won't be flat but you'll get a more natural look and feel. Make sure you don't bury the small ones in grout though
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Damian
Last edited by Sun country customs; 05-08-2015 at 08:08 PM.
Chris, I'm not sure the Kerdi drain will adjust to that thickness. You might do a dry-run with a few pebbles and see, but I think at the very least the drain will have to set below the surface.
As mentioned earlier, concrete doesn't drain water especially well, so you may be dealing with a saturated setting bed, particularly with the pebbles you're using.
I am not using a kerdi drain-I'm using a linear trench drain with the mud deck presloped to 1/4" per foot. The surface of the shower floor can be any height as the water will fall into the trench.
They make sealers for the concrete that would prevent it from absorbing moisture.
Right, forgot you were planning on the linear drain. Once you pour concrete at the proposed depth, can the drain be set high enough to make up for that thickness? I haven't had any calls for linear drains yet so I have no experience with them.
You can certainly use a sealer on the concrete to help with cleaning, but I wouldn't count on it to keep water out.
The top of the drain is level with the mud deck so the water will roll off the edge of whatever is placed on top of the deck into the drain. The edge of whatever ends up on top of the deck will have to be sealed as well as it is effectively one side wall of the drain.
I have been looking at epoxy sealers that will definitely keep moisture out of the concrete...
Anyone have any opinion on how thick to make the concrete layer??? Should I put some reinforcement in it?
I"m planning to make a small, maybe 2'x2' mold, to experiment with...
Ok, so I put down a pre-sloped mud deck using the info here (thanks!), then thinset kerdi and put down pebble tiles.....I haven't grouted them but the problem is they look like crap.
I would like to pour over them a 1 1/2" to 2" layer of something like quicrete sand topping mix with a latex additive and fibers, and seed the surface with 1" to 2" stones, trowel them in nearly flush, then wash off the cream at the appropriate time. I could then grout them as normal. Or do something like this:
Any issues with this idea? Any better products than the sand topping mix?
Thanks in advance.
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Chris
Last edited by Tiger Mountain Tile Inc; 08-05-2015 at 08:58 PM.
Reason: embed vid
I think Kerdi is meant to go directly under the tile + thinset. Sounds to me like you want to put another 1 1/2" of material on top of that.
Might work but its probably not what Schluter wants you to do.
I suggest removing the pebbles and kerdi, re-Kerdi it and choose another tile or pebble that you like.
The other problem is going to be the drain height. If you're adding 1 1/2" to what is already there, I doubt the drain will come up that much to meet the new floor height.
Best to do as Isaac mentioned. The sooner you pull it up, the easier it'll be.
Chris, that video shows what the pebbles look like after they've been grouted. It changes the look of them significantly.
Photo 1: Flat top pebbles before grout
Photo 2: Flat top pebbles after grout
Photo 3: Normal pebbles with grout (sorry. I don't have a before on these types of pebbles)
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James Upton How-to mix a small batch of thinset perfectly, every time.
