There are several variables to consider when determining the proper rafter size.
Roof rafter span sizes.
This sizing guide for roof rafters will help determine what you need for your small project.
2 are indicated below.
Rafter and joist span faq the lengths and sizes of joists vary depending on the species and quality of the lumber used.
This calculator is to be used as an estimating tool only.
Here the number is 1166 66 inches.
Click the button to calculate the stock size needed for this job.
For heavy roofs or in areas with substantial snowfall or winds call your local building department for code requirements.
Publications calculators software building codes fire safety span tables decks weights and measurement codes standards calculators software.
For example you can span a 1 grade no knots southern yellow pine a greater distance than a 2 grade with knots southern yellow pine.
Input the rafter span on the flat eave overhang and pitch of the roof.
Live load 20 lbs ft 2 956 n m 2.
Usually 400 450 or 600mm but any value can be used up to 610mm max.
This calculator is to be used as an estimating tool only.
Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no.
Dead load weight of structure and fixed loads 15 lbs ft 2.
1 ft 0 3048 m.
Live load is weight of furniture wind snow and more.
Rafter stock size calculator.
Rafter run outer wall this should be measured starting from the center of the roof span and then extending to the very edge of the exterior wall.
Click the button to calculate the stock size needed for this job.
Roof rise this should be calculated from the base of the roof to the highest point of the roof gable the peak.
1 psf lb f ft 2 47 88 n m 2.
Here the number is 941 86 inches.
This is the distance between rafter centres.
Weather you re building a shed roof or adding a dormer to your second story it is important to choose the proper size rafter.
For example in the rafter span table below the highlighted cell in the 40 live load table indicates that 2 x 8 southern yellow pine joists that have a grade of 2 that are spaced 24 apart can have a maximum span of 10 feet 3 inches 10 3 if designing for a live load of 40 lbs ft 2.
