I have been looking at the options of counteracting the thrust in low (20º) pitch hipped roofs.
I understand that one of the solutions employed to deal with this is to use ridge and hip beams.
It strikes me that this does not in fact work in timber as even if the beams are designed for 0 deflection the creep over time will still result in the jacks and hip rafters transmitting the full thrust.
If you could calculate exactly how much deflection will take place due to creep and shorten all the rafters in an arc acordingly and only fix them when they are loaded you could overcome this problem but I would doubt whether it was practical to achieve this.
This, I reckon, would also apply in all applications of a ridge beam?.
Following this theory through it would seem more appropriate to counteract the lateral thrust where it is taking place – at the the wall plate. In a vaulted roof construction this is probably best achieved in order of preference by, when possible, tying the opposing external walls together utilizing a perpendicular internal wall, in a masonry structure by using a concrete or steel bond beam (ring beam) and in a stick or SIP construction doing the same with either timber or steel - any difference in the width of the beam and walls being lost into a corbelled soffit.
In an unvaulted roof collars/ties or couples are an alternative but with the exception of couples incorporated into the ceiling, when you are proposing to utilize the roof space, is probably making more work?