Roof Rafter Or Joist

Use this table to determine the maximum lengths of ceiling joists based on species of lumber joist spacing and joist size.

Roof rafter or joist.

Joists attach to beams lying parallel to each other and being aligned horizontally. Continuous ceiling joists or collar ties span from rafter to rafter. The network of joists connects to the rafters distributing the weight of the roof to the beams the roof joists are attached to and thus to the walls of the structure which eventually connect with the. Rafters are the building components that run diagonally from the wall plate to the apex of a roof structure.

Assuming that your builders have chosen to use wood for your house s frame your roofing joists ceiling joists rafters or trusses will be made from long planks of wood placed parallel to one another at evenly spaced intervals along the length of your roof. Collar ties or ridge straps to resist wind uplift shall be connected in the upper third of the attic space in accordance with table r602 3 1. Rafter spans can be extended slightly beyond what the rafter tables suggest when there is a cantelever extending beyond the supporting wall. Where ceiling joists or rafter ties are not provided the ridge formed by these rafters shall be supported by a wall or girder designed in accordance with accepted engineering practice.

Rafters form the foundation for attachment of the roof boards onto which the final roof covering is fixed. Roof supports which are angled are known as rafters. There is no need for bearing posts under the ridge board which is nonstructural. The major functional difference between the two is that trusses are built mostly with 2x4s in place of the wider dimensional boards.

In a typical roof framed with dimension lumber the rafters rest on the exterior wall top plate at the lower end and bear against a ridge board at the top.