Tile over concrete slab WITH pitch

[Wally3433]

This forum is awesome!

I would like to install some ceramic tile over a basement slab, and pitch that tile to a drain in the middle of the room that is 13' x 15'. The drain is not in yet, I will be installing it, so the slab is not pitched right now. The end use of the room is a laundry room, and we will also be kenneling our three dogs in there from time to time. I would like there to be some pitch to help aid in the cleanup of the floors. A couple of questions:

A. Can I pitch the tiles evenly from the edges to the middle of the room by adjusting my thinset mortar? If so, how do I accomplish this?

B. I have enough room for the pitch, in fact, I have a little over 1 and 1/4 inch drop right now at the door from the existing laminate floor (floating on 3/4 plywood and Delta MS). I was thinking of using some Ditra or even Ditra XL to gain some thickness (slab is stable, so Ditra not really needed). Is that a good idea? Other ideas to make up the thickness?

C. Maybe it would be easier to just stay flat at the perimeter, and then pitch an 8x8 or 6x6 section. But even then, what's the best way to gauge the thickness of the thinset?

D. Floor is full of paint spots, adhesives, etc. So I plan to grind the entire surface, then use muratic acid to further etch the surface. Any other advice?

Thanks!

[Kman]

A. You can't use thinset to build up an area and slope the floor. You would need to use a floor patch for that, and even then there are limitations.

B. Ditra and Ditra XL can only be installed on a flat floor.

C. See A. More on this later.

D. Grinding is fine if you can't scrape the spots up easy enough with a scraper to get down to bare concrete. DO NOT use muriatic acid on the concrete for two reasons: 1. The fumes are very toxic and can permanently injure your lungs. Never use it inside your house. 2. It would leave an oily film on the concrete that you don't want.

Tell us what the purpose is of having the entire room sloped to the drain. The reason I ask is because to have proper drainage, the floor would have to be sloped to 1/4" per running foot. To do that, you'd need a slope of 2 1/2" from the furthest corner to the drain, assuming the drain is centered. So you'd have to build up the perimeter of the room 2 1/2", which is not an easy feat.

If you're just wanting to be able to wash the floor down, it would be best just to tile the floor normally and use a large squeegee to push the water to the drain. If the drain is flush with the slab, you can either leave it as is and tile up the drain, or extend the drain up to the level of the tile.

I wouldn't try to slope the floor as you're proposing simply to allow it to drain on it's on unless I was going to wash it every day. It just wouldn't be worth the extra effort.

[Wally3433]

Kman: I see a squeegee in my future. Thanks for the advice. Flat it is.

What type of thinset should I use, purchasing from Home Depot, and what is the thickest I can install thinset?

I was thinking 18x18 tiles since they looked to be the most cost effective and tend to be thicker.

[Kman]

First, I'd say choose your tile, then choose the appropriate thinset.

Thinset is typically good up to 1/4" application (this is after the tile is installed), but it's often combed out with a trowel that has notches up to 1/2" deep. Once again, choose the tile, then choose the trowel.