Five Common Types of Rafters Used for Roof Framing

Rafters form the backbone of most pitched roofs, shaping the overall silhouette and transferring loads to walls. Understanding the five most common rafter types helps builders select the right approach for span, pitch, and architectural needs. Each type serves a specific structural role and pairing it with appropriate joinery ensures durability and proper load distribution.

The following sections describe the five common rafter types, their defining features, typical applications, and practical considerations for installation and compatibility with common roof framing methods.

Common Rafter

The common rafter is the standard, full-length rafter that runs from the ridge line to the exterior wall plate. It forms the main slope of the roof and supports the majority of the roof decking and sheathing. Common rafters are typically consistently spaced and cut to match the roof’s pitch, with birds-mouth notches where they sit on the wall plate.

Key points:

• Used for most simple gable or hip roofs with uniform spans.
• Spacing commonly 16 or 24 inches on center, depending on loads and local codes.
• Cutting involves a precise planing of the top and bottom edges to meet the ridge and wall plate.

Jack Rafter

Jack rafters are shorter rafters that extend from the common rafter to the ridge or to another rafter, filling in the roof slope where the full-length common rafter won’t reach. They help complete the roof shape in complex configurations and can reduce waste by using shorter lengths.

Key points:

• Placed between the ridge line and the common rafter, or between two rafters in non-rectilinear roofs.
• Often cut to match roof pitch and the geometry of hips and valleys.
• Provide necessary support for intermediate sections of the roof without extending full-length rafters.

Hip Rafter

Hip rafters run from the corners of the building up toward the hip intersection where two roof planes meet. They carry much of the load at the roof’s outer edges and create the characteristic diagonal lines seen on hip roofs. Hip rafters require careful layout to align with the ridge and walls, and they intersect with other rafters at precise angles.

Key points:

• Critical for distributing roof loads at external corners on hip roofs.
• Angle and cut complexity increase with roof pitch and building footprint.
• Often paired with jack rafters to complete the hip line.

Valley Rafter

Valley rafters run where two roof planes meet to form a valley. They bear the load of intersecting slopes and transfer it down to the walls, often requiring reinforcement at the valley’s inner corner. Valley rafters must be accurately aligned with both adjoining roof planes to prevent misalignment and water intrusion.

Key points:

• Essential for roofs with intersecting ridges, such as gable-to-gable or hip-valley configurations.
• Valley angles must be calculated to ensure proper seating on both planes.
• Often paired with additional blocking or struts to maintain integrity at the valley.

Scissor Rafter

Scissor rafters are cut the opposite way of conventional rafters, creating a low, dramatic slope when two rafters cross to form a vaulted effect. They are used to achieve a visually appealing ceiling height or to accommodate specific interior design features while maintaining roof integrity.

Key points:

• Creates a vaulted or cathedral-like ceiling without a full ridge beam.
• Requires precise planning for the cut angles and framing members above and below the scissor intersection.
• Often used in conjunction with ceiling joists or temporary supports during construction.

Practical considerations for all rafter types

• Material choice: Southern pine, spruce-pine-fir, or laminated veneer lumber are common, depending on span, local codes, and budget.
• Connections: Metal connectors, joist hangers, and secure nailing patterns improve load transfer and earthquake resistance.
• Code compliance: Local building codes specify allowable spans, pitch minimums, and load factors for different roofing scenarios.
• Insulation and ventilation: Rafter spacing and layout affect insulation thickness and vent placement; plan for airflow to prevent moisture buildup.
• Maintenance: Regular inspections for loose connections, cracks, or wood deterioration help prevent failures in extreme weather.

Choosing the right rafter type begins with the roof design, climate, and structural goals. For straightforward, even spans, common rafters with appropriate spacing are typically sufficient. In complex roof geometries, hip and valley rafters, along with jack rafters, provide the necessary support and geometric integrity. Scissor rafters offer aesthetic benefits with vaulted interiors, but demand precise workmanship and planning.