Follow-up question: how to attend to the detail where roof join?
The flat- roofed extension in question will be attached to a dormer
bungalow. The joists for the flat roof will share the wall plate with
the first floor joists of the dormer bungalow. The top one or two rows
of tiles will need to be removed.
How to join the roofs? A neighbour (who has built his own house)
suggested taking the flat boarding up to the existing rafters, then
removing the bottom row of (large, interlocking conrete) tiles to be
retained, continuing to board up the rafters for a foot or so,
fibreglassing the lot, then putting the edge of the roof underdrawing
back over the sloping bit of the glassed board, and replacing the
bottom row of tiles. That is, no separate flashing material but
continuous fibreglassed board. Does the team agree, or have