After inspecting the roof of my new house, what I first thought was just paint, is actually a hard coating that has been applied to all the tiles, probably 30 years ago or so. It has bonded so strongly to the concrete tiles that removal also removes the top layer of the tiles themselves. The overall problem is that the coating has cracked and allowed a huge amount of moss to grow on the roof. The only options I have are to clean and re-apply a similar coating to achieve an acceptable finish, however, given that the roof is now 80+ years old, I have decided to bite the bullet and replace it, though replace with a clay plain tile, rather than the original concrete. The questions I have are as follows: 1. There are many specifications for new roofs, and many of them run as follows, from the inside: a. ply b. rafter c. Insulation d. Ply e. vapour permeable membrane f. baton g. tile I am wondering what the best option to ask for with regards to both inner and outer ply, membrane and what insulation to opt for. 2. What are the best ventilation options for this roof? The roof is simple; 3 sides, no gables or flat roof parts. advice is appreciated.