So I'm currently giving the house a bit of a makeover and have decided to put new tiles on the bathroom floor, the room is small with the total area tiled approx 1700 x 1200mm. I had thought I'd done my homework after reading up around the web and decided I'd need a membrane or backer board as the bathroom floor is plywood, probably 18mm and according to what I'd read it wasn't a great idea to tile directly onto this. I lifted the current tiles this morning which have been down since we've been in the house (15 years) and they had been tiled directly onto the plywood, no cracks, all very solid etc.. They were like a 300 x 300 x 7mm terracotta sort of tile. Anyway I called in this afternoon to a local tile outlet to purchase some Ditra membrane and explained the situation. They seemed to think with it being small, never had any previous problems I wouldn't need the Ditra and that some sort of S2 flexible adhesive would be grand. Not familiar with the actual brand or what S2 means as I'm a joiner, not a tiler but on their website I've noticed the Mapei brand. They were waiting on a new batch coming in so I wasn't actually able to get it today. What's your thoughts on this? Go ahead with a flexible adhesive? The new tiles are porcelain and 600 x 300 x 9mm if that makes any difference. I mean I'm happy at not having to use Ditra as it's one less step however I do like to do a good and complete job and would rather not have a future headache. One part of me thinks OK, I've never had any bother with the old tiles but at the same time it sort of goes against what I've been reading.