Does anyone have any good online references to design of cathedral ceilings? I don't mean vaulted or raised ceilings (i.e. with scissor trusses), but true cathedral construction. I can see lots of stuff on ventilation issues, span tables etc for normal attic construction, but surprising very little on load and stress design for cathedral ceilings. I've checked the Internet sites of various manufacturers (APA, truss, etc), and would prefer something I can download for free (I'm cheap), but would also be interesed if anyone can recommend a good reference book.

One question for example, is in the absence of ceiling joists or collar beams to tie together the ends of the rafters, how do you account for the forces that would cause the sidewalls to spread? I saw reference to ridge beams as a structural replacment for ceiling joists, but don't understand how that would counteract the spreading forces to the sidewalls.