I have a concrete slab with installed radiant tubes. I want to build a custom shower bed on the slab using kerdi drain and membrane on the walls. Can the shower bed be built directly on the slab or do I need a "slip-sheet" installed between the slab and shower bed? Also, what is the best medium for the "slip-sheet", i.e. felt/poly and lath or can I use Ditra in this application?? I just found your site, what a fantastic resource. Thanks for being there. jwd

You don't need any mesh or "slip-sheet" on the concrete. Just before you place the mud in the shower pan, trowel a layer of modified thinset on the concrete.

Thanks RC, I appreciate the input!! As a newbie at this I wanted to make sure I had my ducks in a row. Thanks again. jwd

Hey RC, I hope your doing fine.

What would you recommend to use for making the mud on concrete, something that may be available at HD.

You can buy bags of all purpose coarse sand and normal(type 10 Canada or type 1 USA)portland cement at the Depot.

I find their concrete sand to have a fair amount of small stone in it. Makes it a little more difficult to work with.

You would be better off going to a masonry supply yard and buying bags of masonry sand.

I still use sand topping mix. Just add water.

Thanks for the advice RC,

The closest to masonry supply yard i can find is in Ottawa and i'm in Toronto, So I guess it's the HD for me.

Your right regarding the stones in the bags from HD which they are bit difficult to work with.

As for the portland bag. I gotta get other stuff to mix.

I was very much looking forward to just purchasing one bag, mix some water and BAM! ready for the mud bed.

Any other suggestion ?

Sand topping that Kman suggested will work, however its a little richer in portland. It's about the equivalent to a 3 to 1 mix.
Some add a little extra sand to the pre bag stuff.

Try Bernardi Building Supply. They have locations in Mississauga and Weston
http://www.bernardibuildingsupply.com/home.htm

I'm new to this site, but have enjoyed the topics. I'm doing my first tile job, DYI, and have a couple of questions if someone could help. First, I am replacing a tub&shower unit with a walk in shower...the unit was 30"x60", and I'm on a slab. So, to build a mud pan,what is the differences between doing the mud bed over a slab as opposed to a wooden floor? Next, I would like to keep the plumbing down to a minimum and use the existing drain, R/H drain. What are the problems with doing it this way as opposed to repluming for a center drain? As I said earlier, this is my first attempt at doing tile and would like to avoid as many mistakes as possible, so any additional info and help would be appreciated. Thanks...Ted

Welcome Ted
It's best to start your own thread thats related to your project.

The difference between concrete and wood has to do with how you start prepping the floor prior to installing the mud and liner.

Please go to General Tile Discussions and start a thread for this project under the Showers/Steamrooms heading.