DIY Doctor UK DIY Forums

I have an extension with a flat roof which can be accessed via a door from a bedroom. The roof is a normal felt on joists type. When built it was covered in tiles for pedestrian use but these have become badly damaged by frost. It will probably be impossible to remove these without damaging the felt, so I am considering laying new slabs on top. What slab/tile would be suitable? Can you advise whether my idea would work. What compound should I use to level the damaged tiles?

I helped tile a flat roof once,I remember he used a very stodgy mix to stop the tiles floating out of position,I would be worried about the weight adding to the existing tiles