View Full Version : roman tub remodel
01-19-2012, 06:59 AM
I'm filling in a sunken roman tub and have a couple of question about the best practice for the slab. I'll use sand for the bottom fill up to where I'll start the concrete slab which will be around 4" thick with reinforced with rebar anchored into the walls, then covered with a mud deck, covered by either kerdi or noble's membrane on the floor with probably hydro ban for the walls.
1) What should I place between the bottom sand and concrete slab? gravel?? I'm assuming I should worry about moisture moving in to out of the slab.
2) The shower will be rectangle with noble freestyle drain running longways in the center of the rectangle. Is it OK to just use the mud deck to create the slope from he drain to the walls? I figure it will be 1 1/4" at the drain rising higher to meet the wall and maintain proper slope. If so, would it suffice to use visqueen between the concrete and mud deck for moisture control?
01-19-2012, 07:13 AM
In case it was not clear the moisture control/movement I'm referring to is for the curing of the cement products.
01-19-2012, 07:29 AM
Sounds like a fun project.
Do you have poly under your exsiting slab? Foam boards? This should be replaced where the tub is sitting.
If your using the Noble Linear drain it needs to anchor to the sub floor. I would suggest you get it on site first and measure the elevations you need.
At 4" of concrete you will be waiting 28 days for it to dry. Or you could buck up for Mapecem Fast Setting Screed Mortar and be laying membrane in 24 hours.
I would set your first concrete layer a 1/4" light of your desired mark so you can shim and set the linear drain perfect.
Kerdi does not allow a tie in with Noble linear drain so using Dal Seal, Wall Seal, CIS or Noble Seal TS is a smarter option.
01-19-2012, 04:11 PM
To maintain a warranty, you don't really want to mix construction methods/materials. If you want to go with Schluter, go with their stuff or stuff they approve; if you want to go with Noble, stick with theirs or stuff they approve; and so on, with each of the suppliers. Each will have certain features/benefits/compatibilities that will dictate which is the best for your application.
Concrete doesn't need to 'dry' (unless you're talking about a modified product with laytex or similar polymers in it)...it cures and incorporates that moisture into its chemical structure. Curing with full hydration creates the highest strength. But, concrete is often mixed with more water than is needed to fully cure which makes it easier to pour and tool (too much and it becomes weak, though).
A conventional slab will give off enough water vapor from excess moisture such that without special considerations, you shouldn't tile it for 28-days.
01-21-2012, 04:04 AM
John thanks for your reply, let me try to describe the project better. The tub/shower is about 12 inches below floor grade. I'm filling it in to make a curbless shower. To raise the existing I plan on filling the tub (area) with compacted fill sand (approx 6") then pouring a 4" slab over it (tied into the existing floor wall with rebar) then topping the new slab with a mud bed to create the slope to the noble linear drain ( which will be anchored to the concrete slab). Then I'll cover the mud bed with the noble liner to form the shower pan. This will take me to the current floor grade. I've allowed for a suitable slope to drive to drive any water away from the shower entrance. I plan on using hydro ban on the CBU walls. So back to my original questions, I'll make the slab out of general purpose concrete (I don't think the Mapecem is appropate for the slab?)
-Wait the full 28 day cure time before I cover with the slopping mudbed...?? I was hoping to give a week or so then cover with poly before putting on the mudbed. It would still be a couple of weeks before I get to tiling etc. I've tried to research this out on the web and forums but there is a lot of conflicting (and more info on wood floor showers) information. Basically relating to the curing of the concrete: If I pour the slab (2' x5') how long before I can start working on it? I was thinking the poly would prevent the mudbed (mortar) from sucking moisture from the concrete, but not sure if that would create a sliding scenario for the two surfaces? I believe from watching the noble install video that the mudbed will be water tight with the noble fabric over the linear drain. What would be the likely outcome if I put the mudbed down over the slab before it "fully" cured?
Thanks, your forums have been a great help.
01-21-2012, 11:33 PM
...If I pour the slab (2' x5') how long before I can start working on it?...
You would be able to work on top of it most likely the next day. But as far as covering the fresh concrete with a mortar bed that needs to wait 4 weeks. This requirement one made by the setting material companies.
I do not understand all the ramifications of covering the mud bed to soon but would think it is not wise since every manufacture of setting materials I have worked with makes a point of stating in their instructions to wait 28 days or work over fully cured concrete.
01-22-2012, 09:05 AM
OK gotcha. In the Nobel video they show putting the water proof fabric over the mud bed then the thin set for tiling. How long before i can tile over the newly set mud bed? Next day I assume?
01-22-2012, 12:30 PM
I would wait three days at least. The Mapecem Screed Mortar fast Setting that I use most times you can cover in 16-24 hours. Many tile setters cover their mortar beds (4-1) the next day and the general rule of thumb is you can as soon as you can walk on it.
With a regular drypack I would be using a standard dry set thinset to cover. When we use the Mapecem I like to use my rapid setting thinsets.
I like to clean my job sites often and we use shop vacs all the time.
A shop vac can suck your Kerdi or Noble right off the mortar bed if it is not set right and allowed to cure. For this reason I use the rapid setting products and work with the noble so I can clean up the next day without worrying about breaking the bond.