Usually 400 450 or 600mm but any value can be used up to 610mm max usually 400 450 or 600mm but any value can be used up to 610mm max 1 2 timber strength class and joist size.
Roof joist span tables uk.
Floor joist span tables for surveyors floor construction.
Span tables for ceiling joists to bs 5268 7 3 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.
Solid timber joist sizes are provided in the bs 8103 3 span tables.
Span tables for solid timber joists.
They also tell you what the maximum spacing should be between each section or timber member.
Solid timber strutting to be at least 38mm thick and be a minimum of three quarters of the joist depth.
Surveyors span tables for designing roof rafters.
Where the tables do not apply or where there are concentrated loads floor joists should be designed by an engineer in accordance with technical requirement r5.
Click on a span to generate a full calculation you can adjust the exact span.
This should be compared to the table.
Rafter spans can be extended slightly beyond what the rafter tables suggest when there is a cantelever extending beyond the supporting wall.
Span tables can be used to determine the size of a timber member of a particular strength class required for a given span.
If your old joists do not meet the requirements set by the table they are either supported.
This is the distance between joist centres.
Ceiling joist span use this table to determine the maximum lengths of ceiling joists based on species of lumber joist spacing and joist size.
Joist spans 2 5m to 4 5m provide strutting at mid span.
Joist spans over 4 5m provide 2 rows of strutting at third span positions.
You need to measure the complete span of your floor joists together with the distance between them the centres and the size of the timbers.
For pitched roofs flat roofs and ceiling joists.
Size of joists mm clear span c16 joist m clear span c24 joist m 47 x 95 47 x 120 47 x 145 47 x 170 47 x 195 47 x 220 1 77 2 40 2 89 3 38 3 87 4 36 2 05 2 67 3 22 3 77 4 31 4 85 assumptions at 400mm centers.
This span table is to the format and methodology given in bs 5268 7 2.
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.
