Hi all, would really appreciate any advice you can give with a bit of a problem!
I've just about finished laying a slate patio, but haven't yet grouted.
The tiles are 600x600x~12mm. I've laid them on a bed of mortar (4:1 sharp sand/cement with a splash of plasticizer) on top of well cured concrete slab. I coated the backs of the tiles with a SBR/cement slurry before bedding them down.
Everything seemed fine at first but now i've noticed that a dozen or so tiles have become loose, and just lift off the bed. The bed is well bonded to the slab, just not to the tile.
This patio gets full sun in the afternoon, so my guess is that the recent cold mornings followed by hot sun in the afternoon has caused enough expansion to de-bond them.
I'd rather not have to hack up the bed and re-lay them, so i'm wondering if I can bond the tile to the bed? As a test i lifted one, marking its orientation, cleaned the back and painted the back and the bed (generously) with SBR slurry, and dropped it back in place. It seems to have stuck fast, but i don't know if this will work for the long term. I would expect that the cement in the slurry should form a decent chemical bond and once grouted it should be fine.
Any advice would be appreciated