What is a jack rafter?

A jack rafter is specifically defined as a rafter that spans from the wall plate to a hip. This type of rafter is used in roof designs, particularly hip roofs, where it serves to support the roofing materials between the main hip rafter and the wall plate. Jack rafters play a crucial role in the structural integrity of the roof, allowing for proper weight distribution and support for the roof deck.

In roof construction, jack rafters are shorter than common rafters, which extend from the ridge to the eaves. Their primary function is to fill the space between the main rafters and the wall, ensuring a smoother transition along the sloped roof line and providing additional support for the roofing materials. This distinction underscores the specialized nature of jack rafters in roof framing, as they are distinct from other types of rafters used for different purposes.