Building Construction Handbook, Eighth Edition

A graceful interruption to the routine of a pitched roof, derived

from thatched roofs where the thatch is swept over window

openings. Other suitable coverings are timber shingles, plain tiles

and small slates.

Main roof pitch >† 50 °. Eyebrow pitch >† 35 °.

Transition curve should be smooth with span to height ratio > 8 : 1.

Less is possible, but may prove impractical and disproportionate.

Possible profile ~

transition curve

window

wallplate

or double

rafter

normal support

30 ° to curve

60 °

A † B is a line through the centre of the window opening.

A † D radius is positioned to clear the window head.

C † D radius is established near window base in continuity to A † D.

A purpose made gluelam beam can be used to create the transition

curve, effectively extending the wallplate to receive the eyebrow

rafters. The curved beam for an intermediate eyebrow may be

supported on joist hangers to double trimming rafters each side.

Eyebrow Dormer Window