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.

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. Continuous ceiling joists or collar ties span from rafter to rafter. Trusses and rafters have many common parts including the sloping rafter boards and a bottom joists that form the ceiling of the space below. Roof supports which are angled are known as rafters.

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. Ceiling joists and rafters shall be nailed to each other in accordance with table r802 5 1 9 and the rafter shall be nailed to the top wall plate in accordance with table r602 3 1 ceiling joists shall be continuous or securely joined in accordance with table r802 5 1 9 where they meet over interior partitions and are nailed to adjacent rafters to provide a continuous tie across the. 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. 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. 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. 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. 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.

Joists attach to beams lying parallel to each other and being aligned horizontally.