Hi all. I will be as brief as possible - please be patient.
I have at the back of my 1930's semi a 14' x 10' flat roof extension - my neighbor has the mirror image on his side so the flat roof is twice my size. It is in good shape - felt with shingle on top.
I am cutting a 7' x 4' hole and building a 150mm upstand (kerb) around the edge to support a new roof lantern.
I understand that I need to dress up the side of the upstand and cap it with lead flashing before attaching the lantern on top.
My question is : how do I weatherproof the old and new felt? Do I push the new felt under the old by a few inches? What about the four external corners - any tips there for dressing?
I have looked and waited for professional help but I need to move things on if possible. I have done a lot of building work and have many tools but have never attempted roofing...
The construction detail is here:
Cheers and thanks for looking!