#ROOF RAFTER SPAN INSTALL#
If you pick Yes, you will also need to declare how much per time unit the contractor would charge you to install the trusses, as well as the expected duration of the installation. The rafter length calculator will return the total expenses in the bottom-most field. If you pick No, the only thing left to input is the cost of a single roof truss. In the appropriate fields of the calculator, decide whether you want to include the cost of installation in the calculations. Our tool can also figure out the approximate roof truss cost. Input the roof length, the on-center spacing (the distance between the middles of two neighboring roof trusses) and the rafter calculator will return the number of roof trusses needed. You can input roof pitch in whichever format you prefer ( angle, percentage, ratio), and our tool will automatically tell you the other ones. You can input any of the two values to get the third one calculated. Here as well, our calculator works both ways. After doing that, you will see the rafter length in the bottom-most field. If you decided to include roof pitch in your calculations, you will need to input the run and the pitch of the roof to get the rafter length. Please note that the rafter length calculator works both ways, that is, you can also use it to calculate the rise or the run! If you already know the rafter length and want to figure out any of the other dimensions, simply input the two you know, and you will get the third one.
You can choose the rise of the roof (which is its height) or the roof pitch (which is the slope created by the rafter). Start by deciding what you want the calculations to be based on. In the field above the illustration, pick either "rafter length" or "truss count". To start your calculations, you need to choose one of the two options mentioned above. You can use it as either a rafter length calculator, which estimates the dimensions of your trusses for you, or as a roof truss count calculator, which will allow you to estimate the roof truss costs as well (it even includes the price of installation).
#ROOF RAFTER SPAN CODE#
With the purlin/bracing installed, the long rafter span would be broken up into two shorter spans, thus allowing the rafter to carry additional load.īefore you make your final decision on lumber sizing and span, consult your local building code officials to determine design loads for your area.Our tool has two applications. You can break up a long span of rafters by installing a purlin and bracing on the underside.
When calculating the span of joists or rafters, use the horizontal distance between to vertical supports. The #1 grade material is more expensive than the #2 grade, but if you can use fewer or smaller #1 grade joists or rafters in your design, youĭepending on the availability and cost of various size framing lumber, it might be more economical to use a larger size joist or rafter in your design, because you can typically use fewer of them. For example, you can span a #1 grade (no knots) southern yellow pine joist a greater distance than a #2 grade of the same species (with knots). The lengths and sizes of joists vary depending on the species and quality of the lumber used. To calculate maximum spans additional species of lumber, use the Span Calculator or the Span Tables for Joists and Rafters on the American Wood Council website.Ĭonsiderations when using the Rafter and Joist Span Tables Contact your local building code officials to determine the building code for your area. Some other regions have special wind and seizmic requirements that should be considered when designing wood structures. For example, some regions get large amounts of snow, whereas others do not get any. Before you can determine the maximum spans for joists and rafters, you must know the load requirements for your given area.