i'm after a bit of advice, i've got a sun room/conservatory in my house (roughly 4.8m x 3.0m), it's basically glass windows all the way round french doors at the front with a flat felt roof (8"x2", ply, 3 layers of felt) on top. see pic
it's been there about 20 odd years and the windows are now rot and beyond repair. i want to replace the windows with upvc, but currently the whole roof is supported by 3"x3" wooden posts which the current wooden windows are built into. This doesn't seem very substantial and because i want to use upvc and these don't have any strength, i need to build some sort of pillars to support the roof and let me build the new upvc frames into.
i thought abouty getting a local bricky in to build some 12" brick piers around the conservatory (4 at the front and 1 other side)
but my question is if he builds these 12" piers there won't be a cavity and damp will travel through the brickwork into the conservatory. is there any way of preventing this?
or is there any other alternative method on the market for what i want, i don't care what i use (although i'm very limited on budget) i.e. upvc cladded support pillars or something.?
any advice wioll be really appreciated.
thanks in advance