I Beam Roof Rafters

Floor live load of 40 psf between the kneewalls.

I beam roof rafters.

Floor beam span tables of residential structural design we will now look at roof rafter and beam design. Here we have a wood framed gable roof. Trusses use webs of 2x4s within the truss structure to support the roof. They are ideal for long spans including continuous spans over intermediate supports.

Rafter spans can be extended slightly beyond what the rafter tables suggest when there is a cantelever extending beyond the supporting wall. If you re framing a gable roof on a new house or building a shed or even a doghouse with a gable roof you ll need to cut a number of roof rafters. Conventional framing the first thing to understand is how a roof framed with wood i joists differs structurally from a traditional stick framed roof. In addition wood i joists are typically stocked and readily available.

Our roof rafter calculator tools are handy for calculating the number of rafters needed rafter length calculator lineal feet of rafter board feed in ridge and sub facia and the total board feet in the roof. If your project had a rafter length of 8 or less a safe and strong method is to use 2x8 framed 16 on center. Straight gable roof framing is assumed for selection table. Ceiling joist span use this table to determine the maximum lengths of ceiling joists based on species of lumber joist spacing and joist size.

It is always better to have a large rafter rather than be concerned with a sagging roof. Continuing on from part 3. Roof dead load of 12 psf asphalt shingles. 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.

Structures such as sheds or barns can be frames with rafters every 24 again make sure to consult local codes. Roof rafter slope between 8 12 and 12 12. Rise and run means that a 6 12 pitch roof has 6 of rise vertical for each foot of run horizontal. A rafter beam is usually larger than a 2 4 large homes may have rafters that are 2 12 or more.

The roof rafters provide integral structural support to the roof. Before you cut your boards you ll need to measure the width of your building and calculate the exact length of each rafter. Attic and floor dead load of 10 psf. Let s consider a basic gable wood roof framing design.

I joists are used extensively in residential floor and roof framing. A truss on the other hand is only made up of 2x4s and is often pre fabricated in a factory. The image below shows a cross section of our simple 12 x 13 house from the joist span tables section of this tutorial.