jack-rafter
- Noun:
- A short rafter: In architecture and construction, a "jack-rafter" is a type of rafter that is shorter than the common rafters, typically used in a roof frame where a hip or valley meets the main roof slope. It does not extend the full length from the ridge to the eaves, but instead connects to a hip or valley rafter.
- (A short rafter used in roof framing.)
- (Short rafters used in complex roof structures.)
"Jack-rafter" in roof framing: Jack-rafters are a key component in hip and valley roofs, where they provide structural support without spanning the entire roof slope. They are often paired with hip rafters (which run diagonally) and common rafters (which run straight from ridge to eaves).
- The roof design required twenty jack-rafters to fill the gaps between the hip rafters. (Short rafters used to complete the roof frame.)
"Jack-rafter" as a technical term: In architectural carpentry, the term distinguishes shorter rafters from full-length common rafters, and they may be further classified as "hip jacks" (attached to a hip rafter) or "valley jacks" (attached to a valley rafter).
- A valley jack-rafter connects the ridge to a valley rafter, while a hip jack-rafter connects the wall plate to a hip rafter. (Two subtypes of jack-rafters.)
Rafter (n): a beam that supports a roof.
- The common rafters were spaced 24 inches apart. (Standard roof beams.)
Hip rafter (n): a rafter that runs diagonally from the ridge to the wall plate at the corner of a hip roof.
- The hip rafter forms the external angle of the roof. (Diagonal roof beam.)
Valley rafter (n): a rafter that runs diagonally where two roof slopes meet to form a valley.
- The valley rafter supports the roof where the two sections intersect. (Diagonal beam at a roof valley.)
- Short rafter: a rafter of reduced length.
- Cripple rafter: sometimes used interchangeably, though "cripple rafter" may refer to a rafter that does not connect to the ridge or wall plate (e.g., between two rafters).