With a scientific calculator (calc set to degrees):Ĭonvert roof pitch to degrees- Degree measurement= inverse tangent of (rise/run)ĭiagonal measurement = Span/cosine of roof pitch in degreesĮnter all lengths in inches for easy mathĮnter pitch in degrees or inches, and press "pitch"Ģ0 "feet" - 1.5 "inch"/ 2= 9 feet 11 1/4 inchĢ0 "feet" - 1. Total rise= (rise/run)*Span (measures from bottom of birds mouth plumb cut to bottom of ridge plumb cut)ĭiagonal measurement=Square root of (span^2+total rise^2) Span= (total roof width-ridge thickness)/2 With a regular basic function calculator (should work with most basic cell phone calculators): ![]() Rule of thumb if the side of the triangle you know falls in the denominator divide by the appropriate trig function if in the numerator multiply by the appropriate trig function.įor a simple gable (example 5/12" pitch, 20' outside of wall to outside of wall, 1 1/2" thick ridge). Lets say we have a 30° rafter with a run of 60"ġ)Identify what trig function to use based on the picture above and what we know about our roof,in this case we need to use the cosine function.Ģ)Make cos(30) a fraction by putting a 1 under it turning it into a improper fraction.ģ)Use the rules of proportion (cross multiply and divide) to solve for the length of our rafter.Ĥ)Cross Multiply-60*1=60 (I know its silly to include multiplying by 1 but its just for those who may not understand proportion) It has a wide range of applications including being used as a wood truss calculator, roof truss calculator, floor joist calculator, scissor truss calculator or. What confuses a lot of people about trig is that they don't understand when to multiply and divide. This free online roof truss calculator is a truss design tool that generates the axial forces, reactions of completely customizable 2D truss structures. Its just basic right angle trigonometry,you would need to use the cosine function to find the length of a rafter knowing only the angle of the roof and the span of the rafter.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |