Joist And Rafter Roof

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

Joist and rafter roof. Continuing on from part 3. The image below shows a cross section of our simple 12 x 13 house from the joist span tables section of this tutorial. They are important load bearing structural elements that hold up both the weight of the ceiling materials for the floor below as well as the weight of any objects or people that may be housed within. The joists might then be covered with osb or plywood to form an attic floor for storage.

Rafters attached to ceiling beams. 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. Roof supports which are angled are known as rafters. The are similar to trusses in this regard.

Builders aren t bound by standard rafter spacing measurements. 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. This board forms the bottom member of each rafter and of course the ceiling of the space below. Here we have a wood framed gable roof.

The roof loads are carried to the top plates of the bearing walls where the floor joists acting in tension keep the rafter ends from spreading out. Continuous ceiling joists or collar ties span from rafter to rafter. Floor beam span tables of residential structural design we will now look at roof rafter and beam design. Rafter and roof joist spacing is only one part of a complex roof design that works together to form a structure that meets building codes and can hold up the weight of the roof and roof load.

In unfinished space an attic insulation is typically laid between the joists. Consult local building codes for snow load capacity and reference the span tables for joists and rafters published by the american wood council awc as a general rule roofs that have a high human occupancy rate should be framed with rafters every 16. A joist is a horizontal structural member used in framing to span an open space often between beams that subsequently transfer loads to vertical members. There is no need for bearing posts under the ridge board which is nonstructural.

Understanding the difference between them is essential for those working in the construction trades while basic knowledge is useful for homeowners if repair and maintenance issues arise. Ceiling joists can be on both low sloped roofs and high sloped roofs and help to prevent racking and spreading of your rafters or walls which could lead to sagging. Let s consider a basic gable wood roof framing design.