Five Common Types of Rafters Used for Roof Framing

Roof framing relies on the right choice of rafters to create a durable, safe, and efficient structure. This article explains the five common types of rafters used for roof framing, their best applications, installation considerations, and code and load implications to help homeowners, builders, and designers make informed decisions.

Rafter Type	Typical Use	Key Feature
Common Rafter	Standard gable and simple roofs	Straight run from ridge to wall plate
Hip Rafter	Hip roofs	Diagonal member forming roof hips
Valley Rafter	Intersecting roof planes	Channels water where planes meet
Jack Rafter	Partial span between hip/valley and wall	Shortened, supports eaves or hips
Ridge Rafter	Roof peak	Central spine that common rafters meet

What Is A Rafter And Why It Matters

A rafter is a structural member that spans from the ridge or hip to the wall plate and supports roof loads. Choosing the right rafter type impacts structural integrity, roof geometry, and water management, affecting long-term performance and maintenance needs.

Common Rafter

Common rafters run from the ridge board to the top plate at regular intervals and are the backbone of most simple roof systems. They form the repetitive structural pattern that supports sheathing, underlayment, and roofing material.

Common rafters are typically spaced 16 or 24 inches on center and sized based on span, roof pitch, and snow or wind loads. Engineered lumber or solid-sawn members are used according to structural calculations and code requirements.

Installation considerations include correct birdsmouth cuts at the wall plate, secure ridge connections, and consistent spacing to prevent sagging or uneven roof planes. They are straightforward to install, reducing labor costs on simple designs.

Hip Rafter

A hip rafter forms the external angle where two sloping roof planes meet. It is a long, diagonal member that supports adjacent jack rafters and transfers loads to the corner posts.

Hip rafters are typically larger in section than common rafters because they carry combined loading from both roof planes. They require precise cutting and layout because their length and angle vary with roof pitch and plan dimensions.

Builders must account for bearing at corners, potential trimming for eaves, and correct nailing patterns. Hip roofs are more wind-resistant and shed water well, but hip rafters add complexity and material cost compared with gable roofs.

Valley Rafter

A valley rafter runs along the internal angle where two roof planes intersect and channels roof runoff into the valley. Valley rafters support valley jack rafters and must resist concentrated loads and accelerated water exposure.

Because valleys collect water and debris, valley rafters require careful flashing detail and often stronger materials. Valley areas are prone to leaks if sheathing, underlayment, or flashing is improperly installed.

Valley rafters are often supported at intermediate points where loads concentrate, and roofers should ensure underlayment and valley flashing are integrated with the rafter layout to maintain a watertight roof system.

Jack Rafter

Jack rafters are shorter members that run from a hip, valley, or ridge to the wall plate, often filling irregular spans. They provide support where full-length common rafters are not practical, such as adjacent to hips or valleys.

There are two main types: hip jacks that run from the wall to a hip rafter and valley jacks that run from a valley rafter to the wall or ridge. Their length varies, so cutting angles and birdsmouths must be carefully measured.

Jack rafters can complicate installation because of many different cuts and lengths. Pre-cut or engineered solutions can speed installation and ensure proper load distribution when dealing with complex roof footprints.

Ridge Rafter (Ridge Board And Ridge Beam)

The ridge rafter joins the tops of opposing rafters at the roof peak. A ridge board provides alignment, while a structural ridge beam can carry significant loads if rafters do not bear on opposing walls.

In simple designs, a non-structural ridge board is used for nailing rafters together. For open-span or vaulted roofs, a structural ridge beam is required to support roof loads and prevent spreading of walls under load.

Selection between ridge board and ridge beam depends on span, rafter bearing conditions, and whether ceiling joists act as ties. Structural calculations or engineered designs should guide the appropriate choice to meet building code and performance demands.

Materials And Sizes For Rafters

Rafters are commonly made from solid-sawn lumber, glued laminated timber (glulam), or engineered lumber such as LVL. Material selection affects span capability, stiffness, and cost.

Solid-sawn lumber (e.g., 2×8, 2×10, 2×12) is typical for residential framing, but engineered options allow longer spans with less depth. Glulam or LVL can reduce the need for intermediate support in open-plan homes.

Local building codes and span tables determine minimum rafter sizes for given loads and spacing. A prescriptive approach using code tables is common for straightforward roofs; structurally engineered solutions are recommended for complex or long-span conditions.

Load Considerations And Roof Pitch

Rafters must carry dead loads (roof materials and framing) and live loads (snow, maintenance) including wind uplift. Roof pitch influences rafter length and loading patterns, with steeper roofs shedding snow but increasing wind exposure.

Designers use span tables and structural calculations to size rafters for combined loads. In regions with heavy snow or high wind, increased member size or closer spacing is often necessary to meet code requirements.

Connections—such as hurricane ties and proper nailing schedules—are as important as member sizing in resisting uplift and lateral forces. Ridge, hip, and valley conditions can create load concentrations that must be detailed appropriately.

Cutting, Layout, And Common Field Practices

Accurate rafter layout includes calculating run, rise, and rafter length using geometry or framing calculators. Precision in birdsmouth cuts, valley and hip angles, and ridge connections prevents misalignment and structural problems.

Common tools include framing squares, speed squares, and digital layout calculators. Pre-fabricated roof trusses offer an alternative to stick framing and reduce field cutting, but rafters remain essential for custom or small-scale roofs.

Good practice includes marking each rafter for its location, creating templates for repetitive cuts, and verifying plumb and level at ridge and wall plates during installation.

Building Code, Inspection, And Durability Considerations

Local building codes specify minimum rafter sizes, spacing, and connections based on load maps and wind zones. Compliance ensures safety, insurance acceptance, and passing inspections.

Durability concerns include moisture control, proper flashing at valleys, ventilation to prevent condensation, and treating exposed members in unconditioned spaces. Pressure-treated sills and metal flashings extend service life in vulnerable locations.

Inspectors often check for correct birdsmouth seating, ridge bearing, nail patterns, and tie-downs. Professional framing or engineered plans reduce the risk of failed inspections and rework.

Cost, Labor, And When To Choose Each Type

Common rafters are economical for simple gable roofs; hip and valley rafters add material and labor costs. Jack rafters increase cutting complexity but are necessary for many roof shapes.

Engineered lumber may cost more upfront but can save on labor and allow longer spans without intermediate supports. Truss systems can be cost-effective for repeatable designs but limit attic space and future modifications.

Decisions should balance aesthetic goals, structural requirements, and budget. Consulting with a structural engineer or experienced framer helps align choices with site conditions and long-term performance.

Maintenance, Repair, And Retrofit Tips

Regular inspections of rafters should focus on rot, insect damage, flashing failures, and loosened connections. Prompt repairs to leaking valleys or compromised rafters prevent widespread structural damage.

Retrofitting for increased loads—such as adding solar panels or insulation—may require reinforcing rafters or upgrading connections. Engineered beams or sistering new members are common reinforcement techniques.

For historic or exposed rafter installations, ensure repair materials match structural capacity and appearance, and use compatible fasteners and flashing to avoid galvanic corrosion and water intrusion issues.

Resources And Tools For Planning Roof Framing

Useful resources include local building codes, span tables from the International Residential Code (IRC), manufacturer literature for engineered lumber, and framing calculators. Professional software and slab-to-ridge calculators speed layout and reduce errors.

Online guides from reputable construction associations and manufacturer tech notes provide detail on nailing schedules, connector requirements, and load calculations. Engaging a structural engineer is recommended for non-standard roofs.

Training courses and trade-school resources help framers stay current with best practices, code updates, and new materials, ensuring safer, more efficient roof framing projects.

Key Takeaway: Selecting the appropriate rafter type—common, hip, valley, jack, or ridge—depends on roof geometry, loads, budget, and desired performance. Proper sizing, connections, and detailing ensure the roof meets structural and weatherproofing demands for years of reliable service.