Timber roof joists are still a popular way of constructing flat roofs.
If the roof joists are just supporting the roof construction then they can be easily designed using load/span tables.
However if the joists are supporting point loads, or acting a trimming beams, then the load/span tables won't cover this.
We need the following information to design timber roof joists:
the span of the joists
details of any unusual loadings
details of any point loads the joists have to support
details of any restrictions on the maximum depth of the joistss
All design work is carried out in accordance with BS5268 (The structural use of timber).
The calculations provided will be suitable for Building Regulation approval.