This is the distance between joist centres.
Timber roof joist span tables uk.
Joist spans 2 5m to 4 5m provide strutting at mid span.
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.
For pitched roofs flat roofs and ceiling joists.
They also tell you what the maximum spacing should be between each section or timber member 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.
Floor joist span tables for surveyors floor construction.
For spans of between 2 5 and 4 5 m one row of strutting is needed at the mid span position.
These span tables apply only to flat roof and roof with a slope of up to 10 degrees.
Timber to be covered these span tables do not apply to timber which is fully exposed to the elements.
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.
Solid timber strutting to be at least 38mm thick and be a minimum of three quarters of the joist depth.
Span tables span tables can be used to determine the size of a timber member of a particular strength class required for a given span.
Notches are not to exceed 0 125 of the depth of the joist and are to be located between 0 07 and 0 25 of the span from the support.
For spans in excess of 4 5 m two rows of strutting will be required positioned at the one third and two third span positions.
Where the joists span over 2 5m strutting is required to prevent joists twisting when loaded.
Timber floor joists shall be adequate for the spans and loads and be correctly installed.
The weight of the timber floor itself consists of the timber joists the plasterboard ceiling underneath it except for suspended timber ground floors the floorboards and the nails or screws used to fix both of the aforementioned coverings.
Solid timber joist sizes are provided in the bs 8103 3 span tables.
Joist spans over 4 5m provide 2 rows of strutting at third span positions.
Proprietary strutting is to be used in accordance with manufacturers recommendations.
Surveyors span tables for designing roof rafters.
