Often asked: What Is A Rafter In Construction?

What is difference between rafters and trusses?

Trusses and rafters are both assembled ahead of being installed onto the roof. Trusses are assembled in a factory using pre-engineered structures and joints. Rafters contain two main outer beams which support the roof structure. On the other hand, trusses come with multiple beams which add more support.

What is the meaning of Rafter?

A rafter is a long board that supports the peak of a roof. If your bedroom is in the attic of your house, you can lie in bed staring up at the rafters. Rafters are a type of beam, a heavy supportive board that holds up whatever is above it in a building.

What is the difference between a rafter and a joist?

The main difference between Joist and Rafter is that the Joist is a horizontal structural element transferring load from flooring to beams, typically running perpendicular to beams and Rafter is a structural members in architecture.

What are rafters called?

Principal rafters are sometimes simply called “principals”. Common rafter (minor rafter): being smaller than a principal rafter. A “principal/common rafter roof” or “double roof” has both principals and commons. (Also called major/minor, primary/secondary).

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What are the 3 types of trusses?

Common types of roof truss

  • King Post truss. A king post truss is typically used for short spans.
  • Queen Post truss. A queen post truss is typically a vertical upright with two triangles either side.
  • Fink truss.
  • Double Pitch Profile truss.
  • Mono Pitch Truss.
  • Scissor Truss (also known as Vaulted Truss)
  • Raised Tie Truss.

Should I use trusses or rafters?

It is certainly true that trusses are more commonly used than rafters. They’re more economical to build and offer the same or greater roof strength. There’s a lot to like. However, trusses don’t give you the opportunity for creativity in home design that rafters allow.

What does purlin mean?

A purlin (or historically purline, purloyne, purling, perling) is a longitudinal, horizontal, structural member in a roof. In traditional timber framing there are three basic types of purlin: purlin plate, principal purlin, and common purlin.

What does eave mean?

1: the lower border of a roof that overhangs the wall —usually used in plural.

What does arresting mean?

: catching the attention: striking, impressive an arresting image.

What size rafters do I need for a 12 foot span?

Max. Live Load 20 lbs/ft2 (956 N/m2)

Maximum Span (ft – in)
Nominal Size (inches) Rafter Spacing, Center to Center, OC (inches) Lumber Grade
2 x 6 24 13′
2 x 8 12 21′ – 7”
16 19′ – 7”

What prevents rafters from spreading?

Rafter ties are installed between opposing rafters, and they should be installed as close as possible to the top plate. Rafter ties resist the outward thrust that rafters exert on the exterior walls. They help keep walls from spreading due to the weight of the roof.

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What is a roof support called?

A timber roof truss is a structural framework of timbers designed to bridge the space above a room and to provide support for a roof. Trusses usually occur at regular intervals, linked by longitudinal timbers such as purlins. The space between each truss is known as a bay.

What do roof rafters sit on?

In a sloped roof, common rafters run from the peak of the roof down to the top of the exterior walls of the building. At the peak, the rafters are nailed to a ridge board, and at the top of the wall, rafters are attached to the horizontal top plate of the wall framing.

What are the main parts of a rafter?

A common rafter has three basic parts you need to become familiar with:

  • Plumb cut, typically called the ridge cut, at the top end of the rafter.
  • Birdsmouth, which consists of two cuts – a horizontal seat cut and a vertical shoulder cut.
  • Tail cut, which may be cut plumb or square, depending on how the eaves are detailed.

What is a four sided roof called?

A mansard roof, also known as a French roof, is a foursided roof with a double slope on each side that meet forming a low-pitched roof.

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