Building components · Frame Members
Hip Rafter
Explains why a hip rafter is a structurally distinct member rather than an ordinary rafter in a corner.
Educational reference entry. What this element has to do, and whether any particular arrangement of it is adequate, depends on the whole assembly, the loading, the exposure, local requirements, the manufacturer's instructions and qualified professional design.
Overview
What a hip rafter is
A hip rafter runs diagonally from the wall plate at an external corner up to the ridge, forming the arris where two roof slopes meet outward. The shortened rafters on each slope frame into it.
Because it collects those members from both sides, it carries considerably more than an ordinary rafter and spans a longer diagonal distance to do so.
Boundaries
How it differs from nearby elements
The distinctions that keep this entry from being a restatement of its neighbours.
- It is not an ordinary rafter. It carries load from two slopes and spans a longer diagonal, which makes it a heavier member with a different job.
- It is not a valley rafter. A hip is an external corner where slopes turn away from each other; a valley is an internal corner where they turn toward each other and where water collects.
- It is not a ridge board. The ridge runs horizontally along the apex; a hip runs diagonally down from it.
Terminology
Common names and aliases
These names describe the same element. The library keeps one entry per component so that a trade term or a regional name never becomes a second, thinner page.
- hip
- hip rafters
Dependencies
What it depends on
What has to be right elsewhere for this element to do its job.
- Support at its foot, where the load from two slopes arrives at a corner of the structure below.
- How the jack rafters on each side frame into it.
- Whether it is supported part-way along its length, since its diagonal span exceeds that of a common rafter.
- The geometry of the roof, since the hip's angle is set by the pitches and the plan shape meeting at that corner.
Considerations
Topics that genuinely apply here
Subjects worth discussing about this element. These are discussion topics, never measured values, ratings or performance claims.
A hip concentrates load from two roof planes at a corner, and the structure beneath that corner has to accept it.
Hip geometry involves compound angles, and setting them out is one of the more demanding parts of a cut roof.
The hip is an exposed arris on the roof, and how the covering is finished along it is a weathering matter for the covering system.
Materials
Commonly formed from
Material families this element is commonly realised in. This states common practice only — it is not a statement that any of these materials suits this component in a particular building, which depends on the whole assembly and on qualified review.
Assemblies
Building systems this element is met in
The role this component fills inside each assembly. A role describes what the element does there — it is not a statement that this component suits that system in any particular building.
Junctions
Interfaces this element takes part in
Junctions where the condition between this element and another governs how the construction behaves. These name the junction and the subjects it raises; they are not details, arrangements or approved ways of building.
Jack Rafter to Hip
Where shortened rafters frame into a hip, delivering the load of two roof slopes onto one diagonal member.
Raises: Structural transfer · Buildability · Weathering
Where it is met
Application contexts
Building contexts where this element is commonly encountered. Association is not recommendation: appearing here does not mean the component suits every instance of that context, or any particular one.
- Pitched Roof
Related elements
Neighbouring components
Typed relationships to other elements. There is deliberately no generic “related” category: an edge that cannot be classified does not exist.
A narrower form of
Clarifications
Commonly misunderstood
- That a hip rafter is the same size as a common rafter. It carries more and spans further, so it commonly is not.
- That hips and valleys are mirror images structurally. They meet different loads and, more importantly, valleys collect water while hips shed it.
Conversations
Questions for qualified professionals
Questions worth asking someone with the project in front of them. This page cannot answer them.
- What is supporting the hip rafter at its foot, and can the corner beneath accept that load?
- Is the hip supported at any point along its length?
- How do the jack rafters connect into the hip?
- How is the covering finished along the hip, and what does that depend on?
Go deeper
Related Build Design Hub guides
Planning guidance behind the decisions this element involves.
Preparation
Related planning checklists
Owner-side preparation before the conversation where this element comes up.
What this entry does not do
- No section, span, angle or capacity is stated here.
- Roof structure alteration, including anything affecting a hip, requires qualified structural design.
Structural Frame Members
The columns, beams, joists, rafters, plates and bracing that make up a load-carrying frame, identified by the position each occupies.
Browse all frame members entries →