Dave Plowman (News) wrote:
In article ,
The Natural Philosopher wrote:
Sorry TNP but I don't buy that argument. Purlins are often very
substantial pieces of timber and with a heavy roof they need to be. Very
few roofs have a pitch greater than 45 degrees so if the load is
resolved into rightangle components only half or less is being
transmitted directly down the rafter.

So where else does it go?

Unless your purlins are actually PROPPED all the weight of the roof is
transmitted via the rafter ends. There *is* no other point of support.

Think you need to look at applied mechanics...

Er. no. Thats what my masters is in.

It seems that the 'purlins' in this case ARE propped - at the gable ends.

And the roof is not a trussed roof at all.