Personally, I would use a bull nose ceramic tile to finish off the sills. You can find these in marble and other finishes. The bull nose edge gives that ready made curve downward, that finishes the edge. They're much cheaper also! That's just my opinion!
That's what I'd suggest to use, if you're set on this type of material for the sills!
Just keep in mind, that your home should be set on a permanent foundation if you have any type solid tile surface in your home.
Ceramic, granite and marble are solid surfaces. Perfect installations require no movement at all. Our homes are designed to move... they travel down highways at 55 miles an hour to get to the site. Please keep this in mind!
It can be done easily, but the upkeep, will much greater than a stick built.
Maureen
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