Curb-mounted skylights are designed for low-pitch and flat roofs, but they can also be installed on some standard pitch roofs. Some installers prefer using curb-mounted skylights even if the type of roof doesn’t call for one to be used. The “curb” is a frame usually made of 2-by-4-inch lumber that is attached to the roof. The skylight is then attached with screws to the curb. Think of it like a shoebox: The curb is the box, and the skylight is the lid that sits on top.
The roof pitch (defined as the angle of the roof) range for curb-mounted skylights is flat to 60 degrees of pitch or 0:12 to 20:12.
Deck-mounted skylights have a lower profile because they attach directly to the roof-deck. Deck-mounted skylights are the choice for new construction or for installing new skylights in existing homes.
The roof pitch range for deck-mounted skylights is 14 degrees to 60 degrees or 3:12 to 137:12.