# Self leveling cement over Tile Thin-set?



## Bushfire (Dec 1, 2008)

I'm in the process of redoing the floor in our guest bath and I'm ripping up the old floor tile.  Thing is that I'm left with a bunch of thin-set on the hardiboard that the previous owner used.  Can I simply use self leveling concrete/cement to fill all the voids and get me back to a flat surface, rather than having to remove all the old thin-set - a painful and almost impossible job.  The hardiboard has also been laid down with thin-set, so it's a real pain to remove back to the subfloor.

I'm thinking a 1/4 inch or so layer of self leveling concrete will get me back to a level sound surface and all I'll need to do is somehow block off the air register and the toilet drain so they don't "fill" with the leveling cement.   I also plan to hold back the cement from the tub sides so that as it dries it won't crack my tub - is this necessary?

Any help/advice would be greatly appreciated.


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## boostnut (Dec 2, 2008)

I went thru the same thing last year. Make sure to remove any loose existing mortar, vacuum the area then follow the directions on the self leveling mortar. If I remember correctly I had to apply a special "primer" for the self leveling mortar to adhere to. Mix it up thin and mask off the edge of your tub. I just used some scrap plywood to block heat registers and the toilet drains. While you're at it you may consider installing an electric heating grid before laying the new tile. I did it and wouldn't have it any other way.


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## Bushfire (Dec 3, 2008)

Thanks, boostnet.  Yes, I did a little more research and asking at HD and I've got the primer and leveling cement to start work tomorrow.  If I had the money, I'd go with the electric heating, bu this is only the guest bath (kids bath once they are older) and it gets used very infrequently.

Thanks again.


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## mjwendorf (Dec 6, 2008)

No need to use level quick. Just spread your thin set over the old stuff and trowel thin set on the back of your tile.


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## Husker21 (Dec 22, 2008)

mjwendorf said:
			
		

> No need to use level quick. Just spread your thin set over the old stuff and trowel thin set on the back of your tile.



i second that.  when we resurfaced our brick mantle with tile we used thin set to fill in the mortar lines on the brick and level out all the adhesive that i couldn't scrape off.  the mantle was previously surfaced with mirror.  hideous.  i will be posting a DIY thread on it soon.


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## wiringlunatic (Jan 1, 2009)

One other thing. Its not necessary to protect the tub -- with the exception of hydraulic cement, mortar shrinks slightly as it dries, it doesn't expand.


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## wiringlunatic (Jan 1, 2009)

Oh, one more thing.  When raising the floor, get a spacer flange for the toilet, don't just try to fill in an extra 1/2" gap with an oversize #10 wax ring (or worse yet, two rings stacked.)


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