Use this table to determine the maximum lengths of floor joists based on species of lumber joist spacing and joist size.
Flat roof joist span calculator.
The truss is a framework consisting of rafters posts and struts which supports your roof.
Size of roof joist 400mm 450mm 600mm 47 x 97 1 84 1 81 1 74 47 x 120 2 43 2 39 2 27 47 x 145 3 08 3 02 2 87 47 x 170 3 75 3 67 3 42 47 x 195 4 41 4 31 3 92 47 x 220 5 04 4 85 4 41 75 x 170 4 50.
Usually 400 450 or 600mm but any value can be used up to 610mm max.
For pitched roofs flat roofs and ceiling joists surveyors and structural engineers utilise data from tables below to help calculate the correct size strength and centres of roof timbers for the required spans and loadings.
Find the column for your dead load and spacing and the row for your timber size to find the permissible clear span in metres.
Span tables for flat roof joists to bs 5268 7 2 imposed loads of 0 75 kn m for maintenance and snow load are applicable where there is no permanent access no fixed ladder or staircase and most areas where the altitude does not exceed 100 metres refer to bs 6399 3.
While every effort has been made to insure the accuracy of the information presented and special effort has been made to assure that the information reflects the state of the art neither the west coast lumber inspection bureau the american wood council nor its members assume any responsibility for any particular design prepared from this online span calculator.
This span table is to the format and methodology given in bs 5268 7 2.
Span calculator for wood joists and rafters also available for the android os.
This is based upon the span of the rafter horizontal span not total rafter length live and dead loads.
1 enter joist details 1 1 span and joist spacing.
To size joists and rafters use the maximum span tables for southern yellow pine.
Also available for the android os.
The full version allows any size.
This rafter span calculator is species specific for douglas fir hemlock etc.
This is the distance between joist centres.
Roof rafter span use this table to determine the maximum lengths of roof rafters based on species and grade of lumber spacing dimensions load and slope.
More roof calculators roof truss calculator how to cut rafters.
The important point to keep in mind when you use your truss calculator is that every truss calculation is completely unique and is based on the size of your roof and its specific dimensions.
Flat roof joist calculator.
