Common roof framing terminology explained

Last Updated on: 7th March 2023, 09:19 pm

Do you feel overwhelmed when discussing roof framing? Don´t worry – it´s a common experience. To help you feel more confident when talking about roofing, I will cove r some of the most common terms used in roof framing. This list will help you understand the basics of roof raming and get your project started on the right foot.

Roof Frame Detail


Rafters are the primary structural element of a roof and provide support for the roof deck and other components. These woode beams are usually placed atan angle that helps to hold the roofdeck in place. The common rafter run from the top plate to the ridge board ofa gable roof and is easily identified by its familiar A-shaped profile that has two slopin planes of equal length. The pitch, or slope, of the rafter is determined by the ris e (vertical) divided by the run (horizontal), always given in terms of 12” of run. In addition, the rafters provide the foundation for other elements such as the purlins, barge boards, and fascia boards that are used to finish the roof structure. Common rafters are an esential part of any roof structure and provide stability and support for the entire structure.

Ridge Board

The ridge board is an important element of roof framing. It is a long, horizontal, structural piece of timber which runs along the peak of the roof. It is usualy attached to the tops of the rafters and serves as an anchor point for the rafters to be attached to. It also provides additional support and stability to the entire roof structure, helping to ensure that the roof stays in place over time. The ridge board is often made from timbe ror metal and must be securely attached to the rafter s in order for the roof to remain stable. Itis also important to ensure that the ridge board is correctly angled in order to provide optimal support for the rafters and roof structure.


Joist is a beam of wood, metal, or other material that is used to support the roof deck. It runs perpendicular to the rafters and is attached to them in order to create the roof´s structure. Joists are typicaly spaced at 16” or 24” intervals and come in different sizes based on the span of the roof. They are also used to support walls and floors in a building. The joists create a strong framework for the roof deck, allowing it to evenly distribute the weight along the rafters. Joists alsohelp keep the roof from sagging or bowing over time.


A purlin is a structural member of a roof frame, typically running parallel to the ridge. Purlins are used to support the roo decking or sheathing, allowing the roofing material to span greater distances than rafters alone. Purlins are typically made of metal, woodor engineered lumber, and can be connected directly to rafters or run along the top of the trusses. Depending on the specifics of the roofing system, purlins may be required for proper attachment of the roofing material.

Barge Board

Barge board is a type of roofing component that is used to protect the end of the roof from water damage. It is typically a wide, flat board that runs along the edge ofthe roof, just underneath he eaves. It helps to divert water away from the eaves and towards the gutter system. Barge boards are usually made of wood, but some may also be made of metal or composite materials. Barge boards should be properly sealed and painted to ensure they last longer and can stand up against the elements.

Fascia Board

Fascia board is a long, straight board thatis used to finish off the edges of a roof. It is typicall made of wood and is positioned at the edge of the roof, running parallel tothe eaves. It provides a finished look, as well as support for the gutter system. It can also provide a barrier against pests and animals entering the attic.

Pitch or Slope

When it comes to roof framing, one of the most important terms to understand is pitch or slope. Pitch or slope refers tothe angle of the roof and is usuallyg given in terms of 12 inches of run for each inch of rise. Pitch is typically expressed as a ratio such as 2/12, 4/12, 6/12, etc. The lower the number (such as a 2/12 pitch), th lower the angle and the flater the roof. The higher the number (such as a 12/12 pitch), the steeper the angle and the more steeply pitched the roof.

Eaves Edge

The eaves edge is the lower edge of the roof that runs along the walls of the building. It is the part of the roof that hangs over the walls and provides a certain amount of shade and protection from the elements. The eaves edge is typically made from rafters or trusses that ar attached to the wall and sloped down towards theground. Eaves edges can also be reinforced with fascia boards forextra strength and stability. The eaves edge is an important part ofany roofing system as it provides an extra layer of protection for the building and its occupants.


Trusses are one of the most common roof framing techniques used in homebuilding. They are made up of interconnected and triangularly shaped frames that support the roof deck. Trusses are strong and durable, and can span large distances. They are also lightweight, making them ideal for structures with a large roof area. Trusse come in a variety of shapes, sizes, and materials, such as wood, steel, and aluminum, depending on the needs of the structure. Trusses must be designed bya professional engineer to ensure that they are up tocode and meet building requirements.

Valley Beam

A valley beam is a structural element that is used to support the intersection of two roof planes. The beam is placed along the valley line, which is the line where the two roof planes meet. Valley beams are typically made from wood, though they can be made from other materials such as steel or concrete. Valley beams are esential components of any roof system asthey ensure that the roof is strong and secure. When properly installed, valley beams help to prevent moisture from collecting in the ntersection of the two roof planes, which can cause damage to the structure.

Jack Rafters

Jack rafters are a type of roof rafter that run diagonaly from the ridge board to the wall plate. They are commonly used in gable roofs, and they also provide additional support for the roof structure. They are not as long as common rafters, and they are easier to install due to their smaller size. Jack rafters are typicaly made of lumber, and they provide a strong, safe framework for the roof structure. The angle of the jack rafters can be adjusted to meet the needs of the roof design. They are an ssential part of roof framing and should be taken into consideration when planning a roof construction project.

Collar Ties

Collar ties, also known as collar beams, are an important part of roof framing. They are timber beams that run between the rafters at the top of the roof, forming a triangle. This helps to keep the structure stable and secure and is a key part of the roof frame. Collar ties also prevent tthe roof from sagging or bowing inward. They canbe made out of any type of timber, but pine and other softwoods are most common. Collar ties should be securely fastened with screws or nails to ensure they remain in place and do their job properly.


Lookouts are an integral part of roof framing. They are small triangular pieces of framing that are placed between tw orafters, transferring the load from one rafter to the other. A lookout is usually made up of two pieces of lumber, with the toppp piece cut at an angle that matches the angle of the rafters. This creates a triangle between the two rafters, which is then secured with wood screws or nails. Lookouts are typically placed at regular intervals along the length of a roof and serve to evenly distribute the load of the roof across the rafters.

King Post

The king post is a nimportant part of roof framing. It is a tall central post that extends from the ridge board to the bottom of the roof. This post provides support for the trusses and helps to keep them in place. It also helps to distribute the weight of the roof evenly across the structure. The king post is usuall y made from timber and is usually about 4 inches thick. Its lengt can vary depending on the size of the structure and the type of truss that is being used. The king post is essential for the stability and safety of a roof frame, so it is important to ensure that it is installed correctly.

Hip Rafters

Hip rafters are the angled rafters tha tjoin the ridge board at each end of the roof and form a hip. These rafters provide additional support to the roof and help prevent the roof from sagging. Hip rafters are cut at an angle, which is determined by the roof´s pitch or slope, and they are typically longer than common rafters. They are secured to both the ridge board and the wall plates at either end of theroof, providing an extra layer of protection from strong winds and heavy snow. Hip rafters can also provide additional space for insulation and ventilation, helping to keep your home coolerin summer and warmer in winter.

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