I'm in the process of fitting my own conservatory (lean-to) and have an original concrete base which slopes away from the house and is below the level of the new floor. I wish to install a floating wooden floor. I will be laying a damp proof membrane over the existing concrete and inserting insulation slabs between the floor joists.
The span of the joists is 2100mm. Would 47x100mm joists at 400mm centres be sufficient to support the floor?
I intend to run a joist along the dwarf wall and original house wall, which will support the joists with hangers. As this is below the dpc, will I need to fit a barrier between the dwarf wall and the timber?
Is there a need to install cavity closures around the dwarf wall opening for the door, as I intend to line the reveal with Upvc?
Anywhere timber needs to be protected from the possibility of rising damp should have a DPC. Its not a bad idea to close a cavity on a dwarf wall even if only for strength, but when it is closed a vertical DPC should be inserted to stop damp travelling from the outer skin to the inner.