Jul 21, 2018
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# How To Work With A Roof Truss Calculator

Roofs can be designed with many attractive styles but the simplest one to build is the open gable. Experts reveal that when roofs are developed by using right hardware, the trusses of these open gable constructions help to distribute the load in even fashion so that the roof can stay stable without any additional support except the walls. In general, the roof truss dimensions are calculated with the help of the Pythagorean theorem because these trusses can be easily reduced to a pair of back to back arranged right-angled triangles. However, the latest roof truss calculator make this task quite easier for professionals and beginners as well.

Before you start working with a roof truss calculator, it is important to understand the roofing terminology. It will help you to perform accurate calculations for all points.

Roofing terminology:

The distance between the outer portions of the wall that support the roof is named as ‘span,’ and half of this distance is called as ‘run.’ While applying the Pythagorean theorem, this run is considered as the base of the right-angled triangle where the height is same as that of the rise of the roof. On the other side, the rafter forms the hypotenuse for this theorem. Note that, most roofs overhang the side walls with smaller dimensions of around 12 to 18 inches and that must be kept in mind while calculating the length for rafter.

Another important parameter in this calculation is ‘pitch’ of the roof that defines the amount of slope for the roof. The mathematicians generally use it as an angle whereas the roofers consider it a ratio. Hence, the roof which follows an estimated rise of 1 inch for the 4 inches horizontal distance is considered to have ¼ pitch. Studies reveal that the optimal pitch is completely dependent upon roof covering.

Use truss calculator to measure rafter length from rise:

Once you measure the roof span, the next task is to determine the rise for a gable roof. This measurement will be completely based on the desired roofing material as well as all essential roofing considerations that an individual is following. This determination also has a direct impact on the overall length of the roof rafters. In order to calculate the dimensions with the help of the Pythagorean theorem, you need to consider the entire truss as back to back, right-angled triangle. The formula used for things calculation is a2 + b2 = c2. Where c represents the length of the rafter, b shows the rise and a is used to define span.

When you are already aware of the rise, you can put all values into the Pythagorean equation in the truss calculator and determine the rafter length for design. For example, in case if the roof rise is estimated to be 7 feet with a span of 20 feet; then rafter length will be equal to 21.2 feet by using truss calculator.

Use truss calculator to measure rafter length from pitch:

In case if you are not aware of the rise of the roof but the estimate about the pitch is clear as per manufacturer’s recommendations or the roofing plan that you are using, it is still possible to determine rafter length with truss calculator. For example, let us assume that the desired pitch is 4/12. It means while considering the right-angled triangle; this ratio shows base dimension to be 12 inches or 1 foot; whereas the rise is 4 inches. Now, using the Pythagorean theorem, the length of the hypotenuse for triangle can be measured as sum of the square root of a and b. That is square root of a2 + b2 or 122 + 42 = 12.65 inches.

In case if you are planning to replace your old roof or want to design a new one for your new home, the roof truss calculators can help you to do quality measurements. These calculators are available to use online as well as offline and can be used by beginners as well. You will be happy to know that a truss calculator can determine the complete cost and material estimate for your structure with specific dimensions. The key inputs used for such calculations are the width, pitch, and roof overhang.

While using a truss calculator, it is important to keep in mind that every truss calculation varies as per the size of the roofing project and the dimensions under consideration. Different types of roof designs have a direct impact on angles of the truss. The truss is actually a framework that is made up of struts, posts, and rafters. Here are some of the most popular types of truss frameworks that designers prefer to use: porch, mono, scissor, parallel chord, room in the attic, cathedral, tray vault, studio vault, and common. While making calculations with the truss calculator, it is important to keep all essential factors in mind.

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