As times are hard I've decided to re-tile my own roof instead of getting some overcharging twit roofer in. I don't pretend to know everything about roof tiling but it can't be that hard. Anyway I've made a start and bought the tiles. I got them at B&Q, 2,760 boxes of the little blighters. Oh, and 800 bags of grout. Not sure about the adhesive though. Should I get the waterproof type?