Roof Vaults
. . . if the roof is a flat Roof Garden, it can be built just like any Floor-Ceiling Vaults. But when it is a sloping roof, according to the character of Sheltering Roofs, it needs a new construction, specifically adapted to the shape which can enclose a volume.
Problem:
What is the best shape for a roof?
Background & Research: Not Included on the site—Go read the book!
Solution:
Build the roof vault either as a cylindrical barrel vault, or like a pitched roof with a slight convex curve in each of the two sloping sides. Put in undulations along the vault, to make the shell more effective. The curvature of the main shell, and of the undulations, can vary with the span; the bigger the span, the deeper the curvature and undulations need to be.
Usage:
Leave space for dormers at intervals along the vault—Dormer Windows, and build them integral with it. Finish the roof with Roof Caps. And once the vault is complete, it needs a waterproof paint or skin applied to its outer surface—Lapped Outside Walls. It can be painted white to protect it against the sun; the undulations will carry the rainwater . . .
pg. 1036