Flat Roof Rafter Layout

Rafter span tables use these tables to determine lengths sizes and spacing of rafters based on a variety of factors such as species load grade spacing and pitch.

Flat roof rafter layout.

For every foot. To lay out a common rafter you need the pitch of the roof expressed in units of rise per foot of run in the gable roof example shown here a rafter with 6 in 12 pitch rises 6 in. If your project had a rafter length of 8 or less a safe and strong method is to use 2x8 framed 16 on center. As a general rule roofs that have a high human occupancy rate should be framed with rafters every 16 structures such as sheds or barns can be frames with rafters every 24 again make sure to consult local codes.

Allow for ridge thickness when determining rafter run to outer wall. The crown will be the top edge of your rafter. Learn the 1 rafter design that will guarantee your roof that is safe and strong for years to come. After you determine the rise span run line length and pitch the next step is to lay out the rafters or mark the cuts on a pattern rafter to create the roof.

The major difference between the warm flat roof and the cold flat roof has to do with the air flow between the roofing timbers known as joists that help to hold up the roof. Using this handy online tool you will have an easy way to determine and figure out the specific rafters needed for the unique slope and dimensions of your roof. Conclusions about the roof rafter length calculator. Laying out hip valley and jack rafters takes experience and skill but if you re building a simple gable or shed roof all you need is the common rafter the basic building block of roof framing.

Print full scale rafter cut templates and birdsmouth templates fold template over rafter to mark or cut through. Half building width minus 1 2 ridge thickness. We will mark the top of the rafter first. This article will discuss a gable roof without valleys or dormers because it s the most common and the easiest for a first time builder to tackle.

Check the rafter material and take note of the crown. This illustration shows an exaggerated crown to get my point across. If you look at the rafter span chart you ll notice that 2x4s can be used for rafters on spans up to 11. See rafter run to outer wall calculator below.

Discover the pros and cons to multiple roof designs. This is our ultimate roof rafter guide for people designing and building an off grid cabin or tiny home. There are design differences for each type. Visit the roof framing page for more information on cutting roof rafters and visit the roof pitch calculator for determining rafter lengths based on rise and run.