Meta Description: Learn about five common types of roof rafters—common, hip, valley, jack, and cripple rafters—and how each supports roof framing.
Roof rafters do more than create a roof’s shape. Together, they form a structural framework that carries roof loads to the walls or beams below. The names of rafters describe their positions, spans, or roles in that framework. Understanding the difference between common, hip, valley, jack, and cripple rafters can make roof plans easier to read and help homeowners communicate with builders. Actual rafter dimensions and connections depend on the building design, local code, material, and expected loads.
How Rafters Work in Roof Framing
Rafters are sloping structural members, often made from dimensional lumber or engineered wood, that support the roof deck and roofing materials. In many conventional roofs, rafters run from an exterior wall up to a ridge board or ridge beam. The ridge is the upper line where opposing roof slopes meet.
Rafters transfer loads—including the weight of roofing, sheathing, and framing, plus applicable snow, wind, and maintenance loads—to supporting walls, beams, or other structural members. A roof’s shape and layout determine which rafter types are needed. A simple gable roof may use mostly common rafters, while a hip roof or one with intersecting sections requires additional members.
Rafters are not interchangeable simply because they look similar. Their span, spacing, species, grade, size, bracing, and connections all affect performance. Building codes and approved plans govern those details. The International Residential Code (IRC), as adopted and amended by local jurisdictions, includes provisions for conventional roof framing. Local requirements may differ, so code compliance should be confirmed with the building department or a qualified design professional.
The Five Common Types of Rafters
Common Rafters
Common rafters are the primary repeating members on many pitched roofs. They usually run from an exterior wall to the ridge, perpendicular to the ridge line. On a basic gable roof, common rafters are installed in opposing pairs, with one rafter on each side of the ridge. Their repeated pattern supports roof sheathing across the roof plane.
On a conventional roof, common rafters are typically cut to the same general profile and spaced at regular intervals. Their layout sets much of the roof’s structure and influences the placement of sheathing edges. The distance between rafters is commonly specified on the plans; it should not be assumed from appearance alone.
At the lower end, a common rafter may have a birdsmouth cut—a notch that seats it on the wall’s top plate. The notch and the rafter’s connection must follow the approved design and code limits. At the upper end, rafters may meet at a ridge board or connect to a structural ridge beam, depending on the roof system. These arrangements are not equivalent: a ridge beam is designed to carry loads, while a ridge board generally provides a nailing surface and helps align opposing rafters.
Hip Rafters
A hip rafter runs diagonally from an outside corner of a building toward the ridge or another roof intersection. It forms the sloping edge where two roof planes meet at an exterior angle. In a hip roof, the roof slopes down on all sides rather than ending in vertical gable walls.
Hip rafters often extend from the building corner to a ridge or ridge intersection. Common rafters on adjacent roof planes connect to or are supported by the hip rafter, depending on the design. Because the hip gathers framing from more than one roof plane, it can carry substantial loads. Its size, support, and connections need to be determined as part of the complete framing design.
Hip rafters are sometimes confused with hip beams or other engineered supports. A rafter’s role depends on the load path and framing plan, not just the diagonal appearance. Roof geometry, span, materials, and local snow and wind conditions all affect the required details.
Valley Rafters
A valley rafter lies in the inside corner where two roof slopes meet. Valleys commonly occur where a main roof intersects a cross-gable, dormer, or addition. Unlike a hip, which forms an outside corner, a valley creates an internal line that channels rainwater down toward the eaves.
Valley rafters typically run diagonally from a roof intersection near the ridge toward the building’s exterior. Shorter rafters from the adjoining roof sections meet the valley rafter. The valley’s location and angle depend on the roof pitch and the geometry of the intersecting sections.
Valley construction calls for careful attention to both framing and water management. The framing must support the intersecting roof planes, while the finished valley needs appropriate underlayment and flashing for the roofing system. Poorly detailed valleys can be vulnerable to leaks, but flashing does not replace the structural support required by the framing plan.
Jack Rafters
Jack rafters are shorter rafters that do not run the full distance from the wall to the ridge. Their names often describe where they connect: hip jacks meet a hip rafter, valley jacks meet a valley rafter, and cripple jacks may fit between a hip or valley and a ridge or other framing member. Terminology can vary among regions and construction drawings.
On a hip roof, hip jack rafters run from an exterior wall to the diagonal hip rafter. On a roof with a valley, valley jack rafters may run from the valley rafter toward a wall or another support. Their length changes along the diagonal member, so they are cut to fit their particular positions.
Although shorter than common rafters, jack rafters are still structural components. Their end connections and bearing conditions matter, especially where several members converge. Plans may specify hangers, fastening patterns, blocking, or other details. Installers should follow those specifications rather than relying on a generic connection method.
Cripple Rafters
Cripple rafters are short framing members used where roof geometry leaves a gap that a full-length rafter cannot span. They may appear near hips, valleys, ridges, or other framing intersections. The exact meaning of “cripple rafter” can vary by trade and drawing, so the plans should be used to identify each member’s intended location and support.
In some roof layouts, a cripple rafter fills a short section between a diagonal rafter and another framing member. It helps carry sheathing or roofing loads in an area where the standard rafter layout does not continue. Its purpose is therefore related to the specific roof intersection rather than a single universal shape or span.
Because the term is not used identically on every project, a builder or designer may label these members differently. If a plan calls for cripple rafters, the framing schedule and details should clarify their size, placement, and connections. They should not be omitted simply because they look like small infill pieces.
Rafter Types at a Glance
| Rafter Type | Typical Location | Primary Role |
|---|---|---|
| Common | Repeated across a roof plane | Supports roof sheathing from wall to ridge or other support |
| Hip | Outside corner between roof planes | Forms the sloping hip and supports adjoining framing |
| Valley | Inside corner where roof sections meet | Forms the valley line and supports adjoining roof framing |
| Jack | Between a wall and a hip or valley, or another support | Fills shorter framing spans around roof intersections |
| Cripple | Short or irregular spaces near roof intersections | Completes framing where full-length rafters do not fit |
How Roof Shape Affects Rafter Layout
A simple gable roof has two sloping sides that meet at a ridge and typically has a straightforward layout of opposing common rafters. A hip roof slopes down toward the walls on all sides, adding diagonal hip rafters and shorter hip jacks. A roof with intersecting wings, dormers, or additions may need valleys and valley jacks.
More complex roof shapes can combine all five types. For example, a main gable roof with a cross-gable addition may use common rafters across both sections, valley rafters where the sections meet, and jack rafters along the valleys. A hip-roof section may add hip rafters and hip jacks. The roof plan and framing details show how these components fit together.
Roof pitch also affects geometry. Pitch is commonly expressed as the vertical rise in inches for every 12 inches of horizontal run. A steeper slope changes rafter length and the angles at roof intersections. A roof’s span, overhangs, and support locations affect the cuts and bearing points as well.
Rafters Versus Roof Trusses
Rafters are assembled on site as part of a roof-framing system. Roof trusses, by contrast, are engineered assemblies made from connected members, commonly manufactured off site. A truss can span between exterior walls and may reduce the need for interior bearing walls, depending on its design and the building layout.
Neither system is automatically better for every project. Rafters can suit custom roof shapes and may allow certain attic configurations, while trusses can provide efficient, engineered framing for many standard layouts. Trusses must be installed and braced according to the manufacturer’s instructions and approved plans. They should not be cut or altered without written approval from the truss designer or an appropriate engineer.
Some buildings use a combination of framing approaches. The decision depends on the design, available space, construction schedule, cost, and structural requirements. A contractor or designer can explain which system matches the plans and local conditions.
What Determines Rafter Size and Spacing?
Rafter size cannot be selected safely by roof type alone. Important design factors include the clear span, spacing, wood species and grade, roof pitch, dead load, live load, and the expected snow and wind conditions. The presence of a ceiling, roof deck, storage area, or heavy roofing material can also affect the design.
For conventional framing, code span tables may apply only when the project meets their assumptions and limitations. Engineered lumber or a structural design may be needed for longer spans, unusual loads, or complex roof geometry. Online calculators and rules of thumb are not a substitute for approved plans or local code requirements.
Rafter connections are another essential part of the system. Ties, connectors, blocking, bracing, and fastening schedules can help maintain the intended load path and resist forces such as wind uplift. The correct details depend on the specific structure and must be coordinated with the roof and wall framing.
Reading Rafter Types on a Roof Plan
Roof plans usually show the roof outline, ridges, hips, valleys, pitch, and sometimes framing direction. A framing plan or detail may identify rafter size, spacing, bearing points, and connections. Common rafters are often represented by repeated parallel lines; hip and valley rafters appear as diagonals. Jack rafters are shorter lines that meet those diagonals.
When reviewing a plan, check the legend and notes because symbols and abbreviations vary between designers. Confirm how a ridge is supported, where each rafter bears, and whether a member is structural or only provides a nailing surface. Questions about unclear or conflicting details should be resolved before framing begins.
Safety and Building-Code Considerations
Roof framing involves fall hazards, heavy materials, and structural work. OSHA construction standards address fall protection and other workplace safety requirements; contractors are responsible for applying the rules relevant to the work. Homeowners should avoid walking on unfinished framing or attempting structural repairs without suitable training and protection.
Permits and inspections may be required for new construction, additions, or structural roof alterations. Requirements vary by jurisdiction, and local officials apply the codes adopted in that area. Before changing rafters, cutting a roof opening, or removing a support, the project should be reviewed by a qualified professional. Even a small change can interrupt the roof’s load path.
For reliable technical guidance, useful starting points include the local building department, the adopted International Residential Code, the American Wood Council’s residential wood-framing resources, and the Occupational Safety and Health Administration’s construction safety information. Plans and product-specific instructions remain controlling for the particular project.
Frequently Asked Questions About Roof Rafters
Are common rafters used on every roof?
No. Common rafters are widespread on pitched roofs, but roof geometry may also require hip, valley, jack, or other framing members. Some roofs use engineered trusses instead of conventional rafters.
What is the difference between a hip rafter and a valley rafter?
A hip rafter frames an outside corner where roof planes meet. A valley rafter frames an inside corner. Both are diagonal members, but they occupy opposite types of roof intersections and support different adjoining sections.
Can rafters be replaced or modified without a permit?
Permit rules depend on the location and scope of work. Because rafters are structural, replacement or modification may require a permit, inspection, or engineered detail. The local building department can confirm the requirements.
Can homeowners determine rafter size from a chart?
Charts can be useful when their assumptions match the project, but they do not cover every roof design or loading condition. Rafter sizing should follow the applicable code, approved plans, or qualified structural guidance.