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I had to repair cast iron pipe in the basement. This left me with a 2ft x 3ft hole in my tiled basement floor. We cut along the grout lines, so I just need to replace the tile and concrete.

Well, I have poured the concrete, but I was not able to get the concrete perfectly level.

On two corners across from each other, when I lay a tile down along those corners I notice the tile is not flat. It it is about a 3/16" inch gap.

I'm inclined to to get some Quikrete leveling sealant to bring everything up to level.

My buddy was mentioning that we could just use the mortar that we are using for the tile to fill the gap.

I'm concerned the tile will crack even with the mortar under it if we don't level it. But is 3/16" of an inch anything to worry about?

What do the tile experts here say?

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2 Answers 2

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Check the manufacturer's specs on the thinset you are using (or just call their tech support to verify).

Generally, if the variation in the floor is 1/4" or more then using your thinset mortar is usually not recommended for fixing it.

Even though you say it is 3/16", in my opinion, it would make life easier to just use an SLC

Ultraplan Easy

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    +1 for the pic.. Self levelers are nice, maybe overkill for such a small area. A couple of coats of thin set or one coat of a medium bed mortar would fill 3/16s
    – HerrBag
    Apr 23, 2013 at 3:39
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    Yeah, you would likely be fine using just your thinset if you don't want to buy extra stuff for a small area. I prefer the ease of SLC, but then again I've usually got extra of that kind of stuff in my workshop or garage somewhere. However, if buying an extra product medium-bed mortar versus SLC, I'd go SLC :)
    – ryanwinchester
    Apr 23, 2013 at 3:43
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    My advice, from personal experience with levelers is 1) buy a "gauge rake" to spread it around with. Using a squeegee will give horrible inconsistent results. 2) as in the picture buying "spiked" sandals is another good idea so you can walk over areas that have already been spread without getting the material on your shoes and causing massive gaps to appear. 3) spritz the floor with a descent amount of water prior to dumping the leveling compound to give yourself more work time. Concrete will immediately begin to suck the water out of your mixture and can cause it to set too fast.
    – TugboatCaptain
    Apr 23, 2013 at 6:35
  • I appreciate everyones input. The SLC looks great and it is not super expensive. But it will add some time to the job. I'm going to check the thinset specs then toss a quarter in the air to decide :-).
    – RDotLee
    Apr 23, 2013 at 11:45
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If you just have 2ft x 3ft there's no problem using usual (not thin-set) mortar to level the surface - it will be cheap (likely cheaper that self-leveling concrete) and quite easy to do.

Thinsets indeed can crack if it's too thick and also they are not very strong - don't withstand compaction as well as ordinary mortar and so there indeed is a chance that you have tiles cracking after thinset applied too thick. How much thick is "too thick" is typically specified by the thinset manufacturer and I seriously doubt that 3/16" (which is less than 5 millimeters) would be a serious problem - that is likely within spec. The problem is you might have hard time applying the thinset so that the tiles perfectly match the uneven surface - it's much easier to do if the surface is even, although my tiling experience is quite limited and I guess there're ways to use the thinset on uneven surfaces and have good results.

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  • Thanks for your input. Between your answer and the previous answer you have given me some good information to think about. Much appreciated.
    – RDotLee
    Apr 23, 2013 at 11:47

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