roof design query / regs
Right. 1992 part A tells me my shallow pitch roof can be just purlins
and sheathing (if I'm wrong then the diagrams are misleading but please someone tell me). This fits in well, since my roof is smaller in this direction anyway. Assuming 0.75kN/m2 loading (snow etc), SC4 timber can do 4 metres at 63x200mm spaced every 900mm. My question is: Can I therefore use e.g. 63x100 every 450mm. This would have an effect on point loading, but could I do this ... or similar ? TIA, Simon. |
roof design query / regs
|
roof design query / regs
I think you are confusing your purlins and your rafters, and sheathing
and laths. The tables and diagrams in the approved docs are quite self explanatory. What are you trying to acheive? dg |
roof design query / regs
I think you are confusing your purlins and your rafters, and sheathing
and laths. The tables and diagrams in the approved docs are quite self explanatory. What are you trying to acheive? No, purlins are defined as beams that span across the roof slope, rafters down. A purlin is not necessarily supporting rafters. The diagram in the 1992 regs for roof 10-30 degree pitch, shows only purlins and sheathing. There is no table for rafters at this pitch - it is like a flat roof. All I am trying to acheive, is to design my roof ! The table I was looking at had separate tables for imposed loads 0.75 and 1.0, and columns for dead loads up to 0.75. I appreciate the bending force rule though, I had forgotten that ! Cheers, Simon. |
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