Roofs of the world
Fifteen roof forms on the same small house (from flat and lean-to to mansard, sawtooth, the Chinese curved roof and thatch), with a common pitch control.
The rules it illustrates
Thatch a third, tile a quarter. Raise a thatched roof by a third and a tiled roof by a quarter: the rougher and more absorbent the covering, the steeper the roof must be.
A pediment is the end of a roof. Put a pediment only where the roof actually ends in a gable, on the short sides of a building, never along its length or stacked one above another, because the pediment represents the gable of the roof.
The hip-and-gable: nine ridges. Combine a hipped lower roof with a gabled upper roof, the triangular gable set back from the end of the building; count one main ridge, four gable ridges and four hip ridges: nine in all.
The mansard: a storey in the roof. Break the slope of the roof on all four sides: a steep lower slope, nearly a wall, which holds a storey of rooms lit by dormers, and a shallow upper slope, often invisible from the street.
The flat roof as a garden. Make the roof flat and use it: a garden and terrace that gives back to the building the ground it covers, drained inward and kept watertight by a continuous membrane.
Name a roof by its slopes. Classify a roof by how its planes meet: one slope (shed), two meeting at a ridge (gable), four meeting at hips (hip, pyramid), a hip below a gable (hip-and-gable), two pitches each side (gambrel, mansard), or a curved surface (barrel, cone, dome).
Where it appears in the book
In the chapters The Roof.