roof beam sizes

I recently put a timber roof on a conservatory and used 4x3 timber for the ring beam and 5x2 for the rafters hope this helps. John JP's Joinery

Hi dave This will depend on how you frame your roof but assuming your spans are less than 1.8m and pitch does not exceed 45 degrees then 5x2 at 600mm is adequate. Purlins may not be required depending on your end connections. You did mention roof trusses so can I assume there are ceiling joists going in? The lightweight tiling and timber will add to the dead weight onto the walls. So be sure that the walls can take additional loads. Also, make sure you're using C16 structural graded timber. Finally it's sometimes best to get a structural engineer to confirm the sizing and detail for peace of mind. Timber suffers terribly from creep so whilst your roof may look fine after 6months, they may bow after 2years.