How to install new tile over this?

Old 09-04-19, 05:59 PM
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How to install new tile over this?

We have old Saltillo tile over this loose sand/concrete mixture the has lots of voids. I’m afraid removing and pouring concrete will be prohibitively expensive. 930 SF total, half of the floor is concrete slab with carpet, half is Saltillo, the surface of the Saltillo is about level with the slab. We would like to install 6” x 36” wood look tile. We have had 3 tile installers out with different solutions and I don’t know which would be best:
1 Install ‘membrane’ over Saltillo then tile
2 grind Saltillo flat and level and feather out over existing slab
3 demo Saltillo and pour some type of leveler into the existing “mud bed”

my question is
1 what is the stuff under my Saltillo and does it need to come out?
2 are any of these 3 the best or some other method?

I know that large format tiles require an exceedingly flat floor and don’t think the first 2 options would work?
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Old 09-05-19, 06:34 AM
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Welcome to the forum.

If the existing tiles are loose, bust them out with a good SDS and start from solid. Tiles don't last if not installed on a solid surface.
Generally with the old houses I've been working on over the years, I tend to lean towards pull what you can out of loose and safe, leave what is solid and not in the way alone.
For most tiles, an SDS hammer drill with a blade chisel will lift the tiles and take you no time at all to get down to solid.

Word of caution with the self leveling, it does not dry 100% flat in shallow fills. You will end up with raised areas. It will also run into any hole or dip it can and will cause you some hate there.
Old 09-28-19, 05:51 AM
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I would do option 3.

its more work, but if you old tiles are on a loose base as you say, it could be a disaster if you then lay new tiles on top.

6 x 36 tiles will need a very flat and stable surface. You should do this right.

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