concrete slab prep

[shovelshort]

I've read posts on this forum and read through John's book but I'm still confused on preping my concrete floor for tile.

I'm finishing a roughed in bathroom in my basement (wall not finished yet). I have already had to break out concrete around shower drain to change it from a 5" drain to a 2" drain. I assume all I have to do is fill in around it with regular concrete until it is level with floor.

Condition of floor - 6 year old slab. The guys that poured it must have been drinking Budweiser at the time because it is pretty uneven (nothing drastic). Surface is painted / sealed. There are some small cracks in the floor but nothing where I am putting the bathroom. I can see under slab from where I broke out the concrete and there seems to be some void spaces between slab and gravel.

I'm not worried about where I am putting the shower pan because I plan on placing tar paper down as vapor barrier and using my pre-slope to make up for any irregularities in the floor. Since I am placing tar paper there shouldn't be any problems about adhering to the slab since the paper keeps that from happening anyway.

My problem is with the floor outside the pan. I'm thinking about using a self leveling cement but I don't know if it will adhere to the painted surface and I don't know if tile will then adhere to the SLC. Do I really need to remove the pain/sealant? How? Does mortar stick to SLC' s or will I have to place kerdi to it before?

Remember, I still need to finish framing so I am still open to making any adjustments to layout. Any help?

[Davy]

Hi Shovelshort, can't remember your name.

I would leave out the tar paper, the preslope is normally bonded to the slab with a slurry of thinset. The pan liner will go on top of the preslope.

The paint needs to come up, it's hard to stick to.

[Levi the Tile Guy]

you might consider a crack isolation membran on your floor also.

[muskymike]

Hi Shovel, you could use one of these to get the paint off. Might be able to rent one from a tool rental.

[flatfloor]

Hi Shovel give us a first name please.

Paint and sealer must come off for a SLC to stick. Mortar will stick to SLCs.

[Alohaguy]

Aloha folks,

Greg here.. I'm remodeling my bathroom and have a fun floor issue. The "house" is on concrete slab ( 6" on top of solid rock, no fill ). The new shower is extended through the wall onto a workshop floor that was poured three years ago. The difference between floors is roughly 1 to 1-1/2". ( the workshop floor is sloped slightly. ) I'm planning on a Kerdi / dry mortar bed shower. I know the floor doesn't have to start out level but how much of a floor difference is sane to fill with dry mortar? I tend to think I'd be better off using SLC plus a little aggregate to fill up the difference and mortar up from there. I just hate working with several different materials if one is adequate.

Ideas?

Thanks...

[jadnashua]

Deck mud should work fine from what I read.

[flatfloor]

Aloha to you too

You need to start your own thread so we can give you our undivided attention. We once mixed up a shower project with a meat freezer. Believe me it wasn't pretty.

BTW, no SLCs in wet areas.

[sandbagger]

yes, much better to mix shower projects with beer coolers.

(Better for us than you, of course.)

[Alohaguy]

Doesn't sound pretty.. I have a low tolerance for cold which is why I live in the tropics.. I was reading through the threads and this seemed more on topic than the others.. I'll move over to a new thread..

[gblentz]

Because the slab we want tiled is so unlevel, all we can hope to do is bring it to flat, so SLC is not involved here. But there is some overspray from when the walls and ceiling were primed, and the occasional small blob of paint. Will mortar adhere to this OK, or does the primer/paint have to be removed?

Gregg

[JTG]

Gregg
So SLC is not going to be used. How are you going to get you floor flat for setting tile. As much work as you can do to get it flat prior to setting the tile will be your reward with a much better looking floor in the end. Unless you have set a lot of tile if is hard to try and level as you to along setting the tile.
Get as much of the over spray and paint off as possible. The ideal slab is one that absorbs water when sprinkled on it. If the water beads it means there is a sealer on the concrete and mortar won't stick. If that is the case you call look to putting something like the EasyMat with the self adhesive back down.
Good LUCK
JTG

[flatfloor]

My problem is with the floor outside the pan. I'm thinking about using a self leveling cement but I don't know if it will adhere to the painted surface and I don't know if tile will then adhere to the SLC

I'm confused I thought you were considering a Self Leveling Cement?

[gblentz]

Thanks Jerry. The floor height within the area to be tiled differs by over 1½" from one end to the other... that would be an awful lot of SLC, and would create a cliff of that height entering two finished rooms at the end of the hallway. The best we can hope for is to bring the floor to "flat" by skim coating with mortar, thereby filling in any surface dips. "Leveling" per se does not appear to be an option for us.