Have some black tiles in our bathroom on one feature wall laid on top of the waterproofing.
What I think is efflorescence or white chalky looking grout has turned the black…

I have some existing slate in the kitchen area and I'm wondering if tilers are willing to tile over the top?
Is that generally a done thing?

Did a small re- lay of bricks on a boundary wall.
Within no time, the bricks I re-layed cracked.
Obviously much a rookie here. Very curious as to what would cause this??…