Five Common Types of Rafters Used for Roof Framing

Roof framing relies on specialized wooden members that transfer loads from the roof to the walls. Understanding the five common types of rafters helps builders plan correct cut angles, spacing, and connections. This article explains common rafters, hip rafters, valley rafters, jack rafters, and cripple rafters, highlighting how each functions in typical roof layouts and how to install them properly in the context of modern American construction.

Common Rafters

Common rafters run from the ridge line down to the exterior wall plate, forming the main slope of a roof. They support the deck and sheathing and carry loads from above. This is the broadest class of rafters in simple gable and shed roofs. Key role: establish the primary roof pitch and shape.

• Usually spaced 16, 24, or 24 inches on center, depending on structural needs.
• Cut with the bird’s mouth notch to seat securely on the wall plate.
• Integral to standard rafter tails and overhangs, often paired with ridge boards and ceiling joists.

In practice, engineers may adjust sizes for wind, snow, or seismic loads. Ensuring proper alignment with the ridge and walls minimizes flutter and provides a stable base for sheathing and roofing materials.

Hip Rafters

Hip rafters run from the exterior corners of the building up to the hip line where two roof planes meet. They carry loads from the intersection of roof planes and contribute to the roof’s overall stability with a diagonal orientation. Key role: transfer corner loads into the interior framing while shaping the hip edge.

• Typically cut at precise angles to meet the ridge beam or hip ridge, depending on the roof design.
• Often longer and heavier than common rafters, requiring accurate layout and support.
• Connection points must be well braced to resist wind uplift and lateral forces.

Architects sometimes use a combination of hip and common rafters to achieve the desired aesthetic and structural performance, especially on complex pyramidal or cross-hip roof layouts.

Valley Rafters

Valley rafters descend from the ridge along the intersection where two roof planes meet, forming a V-shaped channel that channels water away from the roof. They work with common rafters on each side to create a strong, watertight system. Key role: support roof intersections and help manage load transfer where planes converge.

• Often require careful nailing patterns and potentially gusseting at valley joints for added strength.
• Varying thickness and length depend on the valley angle and roof pitch.
• Exterior trim and flashing are crucial to prevent leaks at valley joints.

Proper installation reduces the risk of localized sag and ensures the valley maintains its shape over time, especially in areas with heavy precipitation.

Jack Rafters

Jack rafters are shorter rafters that connect the hip or valley to the exterior wall plate, filling the space between longer rafters. They help shape the roof and provide continuous support for the sheathing around corners and intersections. Key role: fill in-between structural members to complete the roof framework.

• Cut to precise lengths to fit between hip/valley lines and wall plates.
• Require careful measurement to maintain consistent roof pitch along the eave line.
• Commonly used in complex roofs with multiple intersecting planes.

Correctly sized jack rafters prevent gaps in the roof deck and contribute to uniform load distribution across the roof plane.

Cripple Rafters

Cripple rafters are shortened rafters that sit between the wall plate and a hip, valley, or ridge line, helping to form the upper sections of roof planes. They are essential for creating attic spaces and maintaining consistent roof geometry in stepped designs. Key role: fill space above late-cut rafters to complete the roof geometry.

• Hewn or manufactured from standard stock, depending on the design needs.
• Cut with appropriate angles to meet the intersecting member and the ridge or hip line.
• Often require careful calculation in rafter tables to ensure proper bearing and load transfer.

Using cripple rafters accurately preserves headroom in attics and ensures a continuous, tight roof deck across complex layouts.

Rafter Layout Comparison

Understanding these five rafter types helps builders design robust roof frames that resist weather, distribute loads evenly, and optimize attic space. When selecting materials and planning cuts, consulting rafter tables and local building codes ensures safety and compliance in the American construction context.