Minimum roof pitch
Posted: Sun Dec 06, 2009 8:41 amIn building a dormer, I need max height at the low end and therefore need absolute minmum roof pitch. How low can I go?
Hi Mark,
Depends on the roof covering type.
If shingles, most manufacturers say down to 2-1/2:12 slope with some saying down to 1-1/2:12 slope with special underlayment conditions.
If metal roofing such as standing seam, 5-V crimp or similar styles, most manufacturers say down to 4:12 slope.
If concrete tile or slate, most manufacturers say down to 4:12 slope.
If modified bitumen single ply and other similar roofs, most manufacturers say down to 1/4:12 slope.
Also note that the end of the dormer at the window might not need to meet a 7 foot ceiling headroom.