Hip/valley rafter length and jack rafter lengths for a standard square-corner, equal-pitch hip or valley.
Cut the hip/valley rafter at — ft with a —/12 pitch.
Pull pitch from the roof calculator, or override it manually. Assumes a square (90 deg) corner with equal pitch on both intersecting roof planes.
Run the roof calculator first to prefill pitch with the active project roof pitch.
Common rafter run is the horizontal distance from wall to ridge for the roof plane framing into this hip/valley.
Cut the hip/valley rafter at — ft with a —/12 pitch.
Cut at
Included: hip/valley rafter length, jack rafter lengths.
Not included: labor, verification against manufacturer or local-code specifics beyond the reference table used, material waste from cutting.
Diagonal across a square corner formed by two equal-run roof planes.
Shallower than the common rafter pitch, since the hip's run is longer for the same rise.
Length reduction between consecutive jack rafters, one on-center spacing's worth of common rafter length.
Cut length. The theoretical run reaches the hip's centreline, so half the hip's diagonal (45 deg) thickness comes off before it is projected onto the slope. The run listed beside each jack is its layout position and is deliberately not shortened.
Enter roof pitch (or chain it from the roof calculator), the common rafter run for the roof plane framing into this hip/valley, jack rafter spacing, and how many jacks to list.
The standard case: a square (90 deg) building corner with equal roof pitch on both intersecting planes. This covers the large majority of real hip and valley framing. Irregular hips (unequal pitch or non-90 deg corners) are not supported.
Not yet -- this calculator covers rafter lengths and the jack rafter common difference. Compound cheek-cut angles are a planned follow-up.
The hip/valley rafter runs a longer horizontal distance (run x sqrt(2)) to reach the same ridge height as the common rafters, so its unit pitch per foot of its own run is shallower.