Flat Roof Rafter Design

The size of rafters for a flat roof depends on the horizontal span of the building the type and grade of timber used and the load on the roof.

Flat roof rafter design.

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. Here we have a wood framed gable roof. 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. Discover the pros and cons to multiple roof designs.

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. While this article focuses on configurations we also have a very cool set of illustrations showcasing the different parts anatomy of roof trusses. If you want to build a flat roof then you will need to build a flat roof truss these are designed to span the space between two load bearing walls and take the weight from the roof onto these walls. This is our ultimate roof rafter guide for people designing and building an off grid cabin or tiny home.

If you look at the rafter span chart you ll notice that 2x4s can be used for rafters on spans up to 11. The rafters in a flat roof serve as ceiling joists for the space below. The image below shows a cross section of our simple 12 x 13 house from the joist span tables section of this tutorial. If your project had a rafter length of 8 or less a safe and strong method is to use 2x8 framed 16 on center.

A flat roof truss is also known simply as a flat truss and is not completely flat but rather slightly sloped in order to allow water to run off of 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. Conclusions about the roof rafter length calculator. They are nailed securely to exterior wall plates and to each other.

There are design differences for each type. Learn the 1 rafter design that will guarantee your roof that is safe and strong for years to come. Just as there are many types of roofs with many roof parts there are many different types of roof trusses this extensive article explains through a series of custom truss diagrams the different truss configurations you can use for various roofs. Floor beam span tables of residential structural design we will now look at roof rafter and beam design.

The pitch and span of your roof will dictate how long of a rafter you ll need use maximum span calculator to help you find your rafter size. Continuing on from part 3.