Gambrel roofs are double pitched with a break in the roof slope.
The pitch angle above the break is less than 45°relative to the
horizontal, whilst the pitch angle below the break is greater.
Generally, these angles are 30°and 60°.
Gambrels are useful in providing more attic headroom and
frequently incorporate dormers and rooflights. They have a variety
of constructional forms.
Intermediate support can be provided in various ways as shown
above. To create headroom for accommodation in what would
otherwise be attic space, a double head plate and partition studding
is usual. The collar beam and rafters can conveniently locate on
the head plates or prefabricated trusses can span between
partitions.
Gambrel or Mansard Roof