RAFTERS make the depth of the pergola (on an attached, rafters run perpendicular from thehouse). Rafters typically are oriented perpendicular to East/West, as this enables to pergola to create the most shade.

In this photo you can see the rafters that have the contoured tails. Purlin run across the top of the rafters.

The overall depth typically includes an 24-inch overhang on the front and back for a freestanding pergola; on an attached pergola, the front typically has a 24-inch overhang off the front. This determined by measuring from the center of the front/back posts or columns to the end of the rafters. We can make the rafters shorter, such as 18-inches instead of 24-inches. If a Craftsman-style simple cut rafter is desired, then the overhang of the rafter can be even shorter.