Sawtooth Roofs and North Light: Reading Factory Architecture

The jagged sawtooth roofline of the classic mill is a lighting machine. Each tooth holds a near vertical window facing away from the sun, bathing weaving sheds and machine halls in even, shadowless north light that would not glare or fade dyes.

The form spread from English textile mills in the 1870s across the industrial world. Alongside it came the steam powered iron frame, then reinforced concrete and the daylight factories Albert Kahn designed for Ford, with walls of glass.

Once electric light matured, roofs could go flat and halls could go deep, but architects still reach for the sawtooth when daylight quality matters..