I'm in the process of building a conservatory myself and wanted to clear up a few questions i have. It is a Victorian style conservatory with a timber frame and double glazed glass. It will have 2x 14.5ft long walls that join perpendicular to my house (1 dwarf wall and the boundary wall full height) with 3x 5ft dwarf walls at the other end with 135 degree angles. I will access the conservatory from the house by taking out the window at the back of the house and knocking through the wall below. The footings are all dug and i have poured the foundations in and laid the hardcore element of the oversite. The plan is to build a cavity wall and put CavityTherm in the middle and 500mm polystyrene insulation in the floor. I'll lay bricks on the outside up to the damp and concrete blocks on the inside up to the damp. Above the damp will be concrete blocks on the outside, which i will render, and thermolite blocks on the inside. All relatively straightforward so far. I have a few questions on the damp proofing though. My plan is to put sharp sand above the hardcore, lay one large sheet of DPM (1200ga) above this and over the inside layer of bricks and then pour the concrete oversite in. I was then going to lay 1 row of bricks on the inside, lay 450mm wide DPC on this, angle it down to and over the outside brick to allow any moisture that gets through the outside bricks to run off. I'll also take out a bit of the house wall pointing and make sure the DPC is continuous and there is no bridging. I'll the lay the another layer of bricks on the outside to bring it to the same height as the inside wall, then lay concrete blocks on the outside and thermolites on the inside. Once the wall is built, i will then construct the conservatory and do the flashing. Once water tight, i will take the window out and knock through the wall. Once done, i will lay the screed (a little back to front but the only way i can make sure the floor is completely flush with the house floor as i don't want a step). Does this sound like a sensible plan? Do i need to lay a bit of concrete in the cavity above the foundations before adding the angled DPC - i guess it wouldn't do any harm but is it necessary as i would have hoped that it wouldn't be holding much water? Can i simply lay the CavityTherm above this or do i need to put something inbetween? Have i missed anything? Thanks in advance for your help.