What are Rafters? its 7 Types, Construction Steps & Advantages


The rafters are a series of sloped structural pieces that will extend from a ridge area to the plate of a wall and used to support the load of the building and is a structural component of a pitched roof.

The rafters are used as part of roof construction and generally laid in series, side by side providing a base to support roof decks, roof coverings, etc. Rafters are made of timber or steel and can be concealed within the roof structure and to fix the roof covering, they may have battens laid on top and perpendicular to them.


As a key component of various types of roof design, rafters can be used and each rafter is built on the job site using dimensional lumber, and to form the rafter, every piece is measured, cut, and fastened together.

The most common form of the rafter is known as the fink or ‘w’ trussed rafter in modern house construction.

How to Build the Rafters?

There are the following steps to build the rafters as given below;

  1. Mark & Cut the First Rafter Ends
  2. Mark & Cut the Seat and Birdsmouth
  3. Make Set of Rafters From the First Rafter
  4. Make the Rafter Jig
  5. Install the Gusset of First Rafter

Mark & Cut the First Rafter Ends:

The first step to build the rafter is to cut one rafter board to length with the ends angled properly. Then to mark and cut the bird’s mouth and a seat on the rafter and to the angle of the roof slope, the ridge end and often the eve end of the rafter will need to be cut.

Mark & Cut the First Rafter Ends

To make 18 and one half degree angle on the board ends, the roof on this shed should be 4 in 12 slopes. To the long point measure from the eve end of the rafter board and that will be the ridge of the rafter.

Mark & Cut the Seat and Birdsmouth:

The second step will be to mark and cut out the horizontal seat and bird’s mouth, and the horizontal cut is called the seat while the vertical cut is called the bird’s mouth. To the start of the vertical bird’s mouth, measure from the eve end of the rafter and place a mark.

Mark & Cut the Seat and Birdsmouth

To placemarks, all the way across the board on the two points use the square, and to mark the birdsmouth angle, place the pivot point of the square where the birdsmouth mark connects the edge of the board.

Flip the square over and place the pivot point where the seat mark meets the edge of the board to mark the seat cut and then to the birdsmouth depth line, mark a line from that point. Then to its deepest cut setting, set your circular saw and cut along the seat lines and birdsmouth.

Make Set of Rafters From The First Rafter:

In this step to make two more rafters use the first rafter and place the first rafter on second and third boards and then onto the second board trace the bird’s mouth, seat, and ridge angles. Cut the second and third rafters out and prepare them.

Make Set of Rafters From The First Rafter

Make The Rafter Jig:

This step is to build a temporary jig on the shed floor to support in the building by making a line on the exact center of the floor and then the overall height of the rafter assembly is marked from the edge of the shed floor and on the rafter plans, this measurement can be found.

make the rafter jig

At the ridge, the rafter ridges should be fully touching each other along the cuts and along the entire cuts, the seats should be flush with the edge of the shed floor. By one half of an inch, each rafter should be overhanging the edge of the shed floor.

Make sure that the rafter is in its exact position and they are snug up against the rafter edges.

Install The Gusset on The First Rafter:

In this step to attach the two rafters together make a rafter gusset and make sure that the gusset does not extend above the top edges of the rafter. Then by using nails, nail the gusset to the rafters and along the edges of the gusset place a nail every three inches.

Install The Gusset on The First Rafter


On both sides of all the rafters install the gussets and by standing it up and lining it up with the edges of the shed floor test the rafter assembly.

Types of Rafters:

There are the following types of rafters such as;

  1. Common Rafter
  2. Hip Rafter
  3. Hip Jacks
  4. Valley Rafter
  5. Valley Jacks
  6. Cripple Jacks
  7. Flying Hip

types of rafters

Common Rafter:

A common rafter is found in all conventionally framed roofs and run from an exterior wall all the way up to the ridge board and used to set the center the ridge board in the span and height.

In between the principals at both ends, this rafter is located and the hip and valley rafters location can be established after the ridge board location has been established.

Hip Rafter:

This rafter runs at a 45-degree angle to the commons and to the ridge board these are placed from the outside corners of the building.

For the corners of a hip roof, these are used.

Hip Jacks:

This sits on the outside walls and with the common rafters run-up to the hip rafter in line.

Valley Rafter:

Valley rafter is placed at inside corners to the ridge and also at a 45-degree angle and at the lowest point of a valley roof this rafter is found.

Valley Jacks:

These jacks run from the valley rafter up to the ridge board and also in line with the commons.

Cripple Jacks:

When a valley and hip are located close together, cripple jacks are used and only go from a valley to a hip rafter.

Flying Hip:

Flying hip goes from where a valley rafter meets a ridge to the end of a higher ridge board and also known as a mystery hip.

Advantages of Rafters:

There are the following advantages such as;

  1. If you need a lot of unobstructed room up there for storage rafter construction is best for it.
  2. To include a specialized ceiling design like a vaulted or a cathedral style ceiling, the rafters are suitable then.
  3. Less advance planning is needed because rafters are stick-built on-site at the time of need.
  4. At the job site, these take a tremendous amount of time to install.



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