Solid timber joist sizes are provided in the bs 8103 3 span tables.
Roof joist span tables uk.
Rafter spans can be extended slightly beyond what the rafter tables suggest when there is a cantelever extending beyond the supporting wall.
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.
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.
This should be compared to the table.
This is the distance between joist centres.
Click on a span to generate a full calculation you can adjust the exact span.
Solid timber strutting to be at least 38mm thick and be a minimum of three quarters of the joist depth.
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.
Timber floor joists shall be adequate for the spans and loads and be correctly installed.
Surveyors span tables for designing roof rafters.
They also tell you what the maximum spacing should be between each section or timber member.
Floor joist span tables for surveyors floor construction.
This span table is to the format and methodology given in bs 5268 7 2.
Joist spans 2 5m to 4 5m provide strutting at mid span.
Span tables for solid timber joists.
Joist spans over 4 5m provide 2 rows of strutting at third span positions.
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.
Permissible clear spans for flat roof joists to bs 5268 7 2 find the column for your dead load and spacing and the row for your timber size to find the permissible clear span in metres.
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.
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 up to 2 5m no strutting required.
If your old joists do not meet the requirements set by the table they are either supported.
