Minimum roof pitch

[mmarcley]

In building a dormer, I need max height at the low end and therefore need absolute minmum roof pitch. How low can I go?

[Jerry Peck - Codeman]

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.