Leveling a basement slab...

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ToolGuy

ToolGuy

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Basement slabs are never completely level, as anyone setting large tiles on one is sure to find out. I used over 10 bags of Jiff-Set on my most recent basement tile job, just filling the dips as best I could. But the tile really needed a perfectly flat surface, as the edges had no bevel at all (cut square) and the grout lines were only 1/16". I did the best I could with what I had, but still ended up with a lot of edges sticking up. So the question is, if you really need to get the basement slab perfectly flat, how would you accomplish it?
 
ToolGuy said:
Basement slabs are never completely level, as anyone setting large tiles on one is sure to find out. I used over 10 bags of Jiff-Set on my most recent basement tile job, just filling the dips as best I could. But the tile really needed a perfectly flat surface, as the edges had no bevel at all (cut square) and the grout lines were only 1/16". I did the best I could with what I had, but still ended up with a lot of edges sticking up. So the question is, if you really need to get the basement slab perfectly flat, how would you accomplish it?
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Thats a big problem for most people that dont set tile day in and day out. Self levelers like you used is the way to go. After that I would suggest using a large notched trowel. 1/2 inch square notch is nice for this but you need to make sure the thinset isnt mixed to thin or youll find the tile will settle. With rectified edges like the tile you used, you can use a marble thinset. The gritty mixture will reduce or totally hault settling all together.
I once did 500 square feet of marble on a slab that the homeowner didnt want to level. The slab in some rooms dipped 5/8 from the center of the room to the corner. The room being 10x10 ! It took forever to get right, we used 1/2 inch trowels and in some cases used a 1/4 inch trowel to "butter" the back of tile to float it and create that flat "glassy" look. Ill try to find the pics of that one.
If the floor is as bad as the one I tiled, I would suggest leveling it from one end to the other.
 
The job is already done, but there will be a next time to be sure. I used a 1/2 notch and had to butter some tiles to get 'em even. The customer is exstatic with the finished floor, but my trained eye is not satisfied. Of course, I keep that to myself. I spent 2 days filling the slab and it still wasn't flat enough for these tiles, or my rather high standards. Maybe next time I just have to spend 3 days filling. :eek:
 
I've run into this a few times. For slight out of level situations, I do what both of you have done: 1/2" notch to get max flexibility when setting the tiles.

I have also had situations where the out of level was too much to correct with a big notch trowel, so I dammed the area and leveled it before I set the tile.

With a 1/16" grout line, it's going to be difficult any way you do it. My bathroom floor has narrow grout lines and there's absolutely NO margin for error with marble tile. I've got some ridges. :eek:

Wider grout lines work out better, but don't look right with some tile/marble.
 
as gc's but do dec conc enhancements ourselves,,, residential flatness is always suspect,,, you might consider gypsum self-leveling mixes but downside's the owners rarely go for the long $$$ as most h/o's are cheap.

when we run into this work, we either use scarifiers & grinders to level OR we don't take the work.
 
You could have pumped out Self Leveling Compound and had a perfectly flat, and level surface to tile over.
 
I have this issue with a downstairs bathroom with concrete slab subfloor. It's surely out of level, just looking at it with the naked eye you can tell. We're going to lay 16x16 tiles.

Can someone give me some more specific tips on using this self-leveling stuff?

Brands? Techniques? Other tips?


Thanks!
 
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