Roof ridge offset for overlap shingles on roof edges

Hi All:
So I finished most of the modelling for a house, and I want to realistically texture the roof shingles. To do so, I want all ridges to have an offset from the edge so I have a face on each side to texture the ridge shingles texture. The roof is created…is there a simple way to offset the edges approx. 6" on each side of a peak I want to apply that texture to? each method I try is cumbersome and imprecise.

Attached image of my model highlighting an edge I want to offset, and an image of what I am looking to model:

Thanks in advance