supporting. That part from D to B is what is
generally termed blind valley, because it is con-
cealed in the plane of the main roof. The meas-



FRAMING



107



urement should be taken along the center of the
back of the valley, as shown by the dotted lines ;
and if backed — or, more properly speaking,
grooved, so that the roof boards will have a solid
bearing at aU points — ^then the seat cut should
be made so as to bring the grooves in the plane
with that of the back of the common rafters.
This furnishes a problem in itself that is not so



Section of
Blind Valley




Fig. 60. Intersection of VaUeys — ^Boof Donners.
easily understood as may appear at first sight,
especially where there is a projection of the
rafter to form the cornice.
However, it is not usual to groove the val-
leys, as they are generaUy concealed from view
and otherwise not of enough advantage to war-
rant the extra work required. Where they are
not grooved, they should set proportionately



108 FRAMINa

lower than the common rafter, so that the mider
edge of the roof boards will intersect the center
of the back of the valley. Even then, that part
from D to B would have to be backed or beveled
on one side the same as for a hip, to bring the
center in plane with the common rafter.
