Skillion roof beam?

[cammo1]

Hi , this is my first post here as we are planning a small renovation on a workers cottage in Brisbane. I have read the forum for a while now and have a query on the design of a roof.

It is a 6 m long skillion roof that will extend from the rear of the house. It is 7 m wide that will be split into an additional room and a deck. Ok my query is the design of the rafters and how they sit. The plans call for a pitching (intermediate) beam in the middle of the span and the rafters sitting on this beam and on the top plate at the end. At the end I was planning on birdsmouthing the rafters, but am unsure on the attachement to the pitching beam.

The plans call for framing anchors on each rafter, but what about the way they sit on the beam? should they be birdsmouthed in the middle, wedged or the beam angled to suit the fall of the rafter (al la an underpurlin). Or could the rafter sit on the edge of the beam with a framing anchor taking the weight.

I hope this is reasonably clear and thanks for your time.

Cheers

Cammo

[silentC]

Not sure what the requirements would be but if it was me, I'd set up the ledger, pitching beam and top plate so that their forward edges are in line, then I'd birdmouth the rafters around all three. The framing anchors are for tie down and I think I'd like to have good contact on top of the beams for load bearing.

Someone else may know whether it's necessary or not.

[ausdesign]

As silent said.
The reg's require full support of the rafter whether it be by b'mouthing, timber wedges etc. - max. cut out one third the depth of the rafter.
I definitely would not angle the beam as this reduces its loadbearing capacity, all be it small - depending on the amount of rotation.