I Beam Roof Rafters

Rise and run means that a 6 12 pitch roof has 6 of rise vertical for each foot of run horizontal.

I beam roof rafters.

Continuing on from part 3. 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. Conventional framing the first thing to understand is how a roof framed with wood i joists differs structurally from a traditional stick framed roof. Roof rafter slope between 8 12 and 12 12.

Because i joists are straight and true it s easier for builders to avoid crowning and maintain a level framing surface. I joists are used extensively in residential floor and roof framing. It is always better to have a large rafter rather than be concerned with a sagging roof. 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.

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. They are ideal for long spans including continuous spans over intermediate supports. Trusses use webs of 2x4s within the truss structure to support the roof. The image below shows a cross section of our simple 12 x 13 house from the joist span tables section of this tutorial.

The roof rafters provide integral structural support to the roof. Floor beam span tables of residential structural design we will now look at roof rafter and beam design. Ceiling joist span use this table to determine the maximum lengths of ceiling joists based on species of lumber joist spacing and joist size. Kneewall weight of 40 plf.

Rafter spans can be extended slightly beyond what the rafter tables suggest when there is a cantelever extending beyond the supporting wall. A rafter beam is usually larger than a 2 4 large homes may have rafters that are 2 12 or more. A truss on the other hand is only made up of 2x4s and is often pre fabricated in a factory. Attic and floor dead load of 10 psf.

Attic storage load of 20 psf live load outside the kneewalls. If your project had a rafter length of 8 or less a safe and strong method is to use 2x8 framed 16 on center. Roof dead load of 12 psf asphalt shingles. Straight gable roof framing is assumed for selection table.

Let s consider a basic gable wood roof framing design. Structures such as sheds or barns can be frames with rafters every 24 again make sure to consult local codes. Before you cut your boards you ll need to measure the width of your building and calculate the exact length of each rafter.