Doing a job at the moment tiling onto floorboards, using a flexible adhesive but do i use a flexable grout or a normal floor grout?

Hi graham, Over here we tile mostly on concrete slabs even on highrises. If I did tile over boards I would durrock it first. I am working on modulars homes now and they do not durrock on top of plyboards.(cement board)I was very concerned about this and questioned this. I was told to use flex bond and a flex grout. I feel you still need to use caulk around doors and base boards because I noticed they still crack so I woiuld say yes to you question use flex grout. We use poly blend a custom product.

Thanks for all your replies, i ended up tileing onto plywood and using flexible adhesive & grout, and it looks great.