rafter size/grade

hi as this is such a small span or roof i would recomend graded 5x2 timbers which can also be used for the ceiling ,at 16 in centres this is more than adecuete and will keep with building regs ,but it wont hert to contact any building control if you are using one ,you wont need to use purlins ,you will have to use joist hangers on wall side ansd best to birds mouth the fascia end

150mm by 50mm stress graded timber would be sufficient for this span and 125mm by 50mm for the ceiling would be fine. Purlins are only used for big spans where the rafter is likely to sag e.g house roof or large extensions.

I would agree with D&N on the size of timbers to be used, use c24 grade timber. I would also add, just make sure you bolt the ridge plate (top of Rafters)to the wall well using thunder bolts etc. Also the plate at the ends of the ceiling joists. ps why not ask your building inspector?!

6x2 at 400 centres purlins not required c16 or c24 grade timber

6"X2"graded timber

Hi there 5x2 graded timber for rafters and ceiling joist as 6x2 is only used in loadbearing situations and would be cheaper than 6x2. No need for purlins it would be a steel beam you would need to use but that is not necessery as it is only a lean to roof.

Hi, 150mm x 50mm C16 graded timber - any roof work. 100mm x 50mm graded or ungraded timber - ceiling joists. Hope this helps. Matt Norman.