Designing Kitchens and Bathrooms - Suggestion for replacing floor tile

Hi,

I'm trying to update my bathroom, and I've removed the floor tile to find that the floor has a 1 inch or so of build-up (...I'm assuming that it's a leveling agent) from the concrete slab. The bathroom is really small. The tub is not on the build-up only the toilet.

My question is, why would there be such a high build-up of a crumbly concrete-like substance. For the most part, the slab is pretty level through out the home?

While removing the old tile, this build-up has cracks and holes that developed while I was chipping away at the tile. My first thought was to remove the build-up substance, since it was coming apart, and reapply the new tile to the concrete slab. Then I thought that maybe it was built up for a reason.

Where the toilet sits, there is a dug out area where the flange is. I'm assuming that because the build up is so high, the installers of the toilet had to dig up some of the build up to install the toilet.

If any of this makes any sense to you, please HELP ME!!!

That was a shortcut to avoid moving the flange, which should be done. Flange top should be flush to slightly above finished floor level, with no humps or holes as a fudge factor.

The 1" mudbed was likely installed to make a perfectly flat surface to accept the tile. It's done all the time. If its cracked and crumbly, its gotta go so remove it. Evaluate the slab afterwards as to flatness and let us know what you find.:)