Rafter

**Types of Rafters:**
– Principal rafter: larger rafter landing on a tie beam
– Common rafter: smaller than principal rafter, part of double roof
– Auxiliary rafter: secondary type supporting principal rafter
– Compass rafter: curved or bowed rafter
– Curb rafter: upper rafters in a curb roof
– Different types of historical rafters like hip and valley rafters

**Applications and Advantages of Trussed Rafters:**
– Preference for trussed rafters in recent buildings
– Trussed rafters offer cost and material efficiency
– Trussed rafters allow for off-site manufacturing
– Trussed rafters provide ease of construction
– Trussed rafters have design advantages like span limitations

**Historical Evolution of Rafters:**
– Early European roofs featured common rafters on a tie beam
– Evolution to major/minor or primary/secondary roof systems
– Tapered rafters to optimize strength with less lumber
– Purpose and design considerations of historical rafters

**Reinforcements and Supports for Rafters:**
– Strut, principal purlin, collar beam reinforce rafters
– Auxiliary rafter is a rare type of support rafter
– Different types of rafter reinforcements like knee and barge rafters
– Binding rafter, cruck frame, and LVL rafter details

**Materials and Specifications:**
– Rafters traditionally made of pine or cedar
– Longer span rafters use LVL (Laminated Veneer Lumber)
– Maximum length of wood rafters in the US is 20 feet
– LVL offers longer span alternatives for rafters
– Building materials and specifications for rafters

Rafter (Wikipedia)
This article is about the structural beam. For other uses, see Rafter (disambiguation).

A rafter is one of a series of sloped structural members such as steel beams that extend from the ridge or hip to the wall plate, downslope perimeter or eave, and that are designed to support the roof shingles, roof deck, roof covering and its associated loads. A pair of rafters is called a couple. In home construction, rafters are normally made of wood. Exposed rafters are a feature of some traditional roof styles.

Common rafters without collar beams form most of this roof. There is not always a ridge board or beam where the rafter tops meet. Under the midsections of the rafters are purlins which support the common rafters and are supported by principal rafters. This roof ends in an octagonal hip.
A double roof (using a Norman truss), common rafters supported by principal rafters (top chords in this case) and an unusual extra layer of common rafters on the lower half to form a gallerie. Note how the rafter poles for the gallerie tie-in. The Bequet-Ribault House was built c. 1793 near Ste. Geneviève, Missouri. It is one of five poteaux-en-terre buildings that survive in the US.
Rafter and tie-beam joints (Carpentry and Joinery, 1925)
Coyau or sprocket. Labeled A

Definition from ChatGPT:

Rafter:

A rafter is a sloping beam that supports the roof of a building and runs from the ridge or hip of the roof to the eaves, providing structural support for the roof covering. Rafters are typically made of wood or metal and are spaced at regular intervals across the roof structure.

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