The main difference between a pergola and a gazebo is the roof. The roof of a pergola is typically an open grid of beams, rafters, and purlins (which run perpendicular to the rafters), usually ...

The total size of the screen house DIY gazebo at the roof is 18 feet by 15 1/2 ... Overlay the plywood onto the 1x6 and nail it through the plywood and roof boards into the rafters with 10d nails.

Double up the rafters. If you're creating a dormer on a roof framed with common rafters, you'll need to double or triple up the rafters on either side of where the dormer will be.

I gave lots of thought to the simple rafter tails in my pergola how-to article in PM's May 2009 issue. That one's a swooping semicircle combined with a miter cut.

Rafters are made from sloped framing boards of dimensional lumber -- usually 2x8s or 2x10s -- connecting the roof peak, known as the ridge board, to the plates of the exterior walls. They are ...