for some applications I'm a fan of SIPs on roofs. large simple spaces that you can cover quickly. let the TF remain below with TG sheathing pre-applied to the frame, set on the SIPs and detail for the type of roof surface you want. depending on lateral load requirements you may be able to get curtainwall panels (OSB only on 1 side) to do the job...
or following tim's lead on not having 2 structures - simplify the timber frame to work with a conventional built roof. use principle purlins, ridge, and plates to hold up 2x rafters (or even TJIs, etc.) at the depth you need for insulation. use a spacer between the timber and the conventional framing, over frame and sheath the outside (add a hi-r or similar if applicable to limit thermal bridging), blow full of foam or cellulose from the inside, then attach interior finishes from below... lets the timber do the work. and combines conventional framing into a logical way to hold up the roof and insulation. but if you want to save $$ and redundancy you will probably leave out common rafters or common purlins, although I've seen it done either way.
Last edited by bmike; 01/21/10 01:45 PM.
