Discuss Re-grouting job shows up cowboy work in the General Off-topic Chat (nothing tile) area at TilersForums.com.
Depends what’s caused the crack. Sometimes they occur when extensions or alternations are done or subsidence.
Provided there is no further movement, I would dot and dab either plasterboard or tile backer board. Depending on weight of tiles.
I'd be chiseling out those cracks and repointing, don't want them ringing me back with cracked tiles.
If the they used thermalite blocks for the extension about as much use as an ashtray on a motorbike for tiling on.
As already recommended dry wall would be the best option.
Reply to Re-grouting job shows up cowboy work in the General Off-topic Chat (nothing tile) area at TilersForums.com
Or checkout our tile courses and training forum or the Tile Blog / Latest Blog Posts