I have removed 9x9 ceramic tile over cement, I was wondering how clean do I have to have the cement from the old mastic to install 20x20 ceramic tile.

Get the adhesive removed to be just a staining and then choose any thinset that lists old cutback adhesive as one of the things it can be spread over. The old cutback adhesive may contain asbestos so wet an area before scraping it with a 4" wall paper scraper. Suck up the water with a shop vac with a hepa filter, and tile away.

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Originally Posted by wayneeford

I have removed 9x9 ceramic tile over cement, i was wondering how clean do i have to have the cement from the old mastic to install 20x20 ceramic tile.

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cutback wouldn't be used to set ceramic tile and I sure hope mastic wasn't used too.

Your going to need to remove the old thinset left by grinding or floating over it with a thinset or and SLC

CERAMICTEC!!! CERAMICTEC!!!

:eek: :eek: :eek:

WHO INVITED THIS GUY?!

Hey Bri, what's up? Welcome, my friend. :)

Grinding and scraping is the way to do it, if you have the right grinding disk it's a non problem