I've recently purchased a house in Philadelphia which has a pretty humid basement split into a finished part, and an unfinished (workshop) part. The finished part has a slate floor that seems in reasonable condition, but it is requires some grouting. In a few places there are loose tiles and a few small parts where a layer from the corner of a slate tile has come off.
I suspect the previous owner may not have a performed any recent maintenance or sealing. I'm probably going to get a specialist, but what should I be looking for in terms of products and approaches to sealing this floor? I'd prefer to keep a more natural look. Given the hot and humid weather here in Philly I suspect I'll need to wait until spring or fall to do this work as the basement is my office space.