But a gable roof also requires some form of horizontal.
Gable roof roof bracing.
A standard triangular roof known as a gable roof is framed using rafters which are diagonal members that support the roofing materials.
What makes a gable roof what its higher pitch than ordinary roofs.
In the attic go to the gable end and examine the area where the triangular wall meets the rectangular wall below.
This higher pitch is going to mean that bracing your gable roof is important.
Gable end walls need to be well connected to the wall below and to the roof structure or ceiling diaphragm.