I'm designing a new home and most likely will be building with SIP walls and roof using attic roof trusses. I'd like to have exposed rafter tails but am not sure of the best way to build it. I'd appreciate hearing from anyone who has had some experience with this idea. The house will be 26' x 42', roof pitch will be 10/12. Is it a good idea to use the same or greater than wall thickness panels on the roof?

Typically roof sips are 8, 10 or 12". It usually depends upon your span. In your case you can use any core size, the main factor is what r-value you would like. For the exposed tails, I have used no-1 4x material for joist. Cut your sip's flush with the wall and run the joist as long as needed.

Hope this helps
If you need a detail just ask

Similar to what san diego described, we use 2x splines, stop the SIPS at the wall and let the 2x's fly by to form the overhang. This works for exposed or enclosed overhangs, either.

What if you don't want the rafter tail to be the same depth as the panel? As in a 10" panel with an 8" rafter tail. Perhaps a detail would be helpful. Thanks

On the house I'm building, we ran the panels two feet past the wall for the overhang, then attached faux beam tails to the underside with panel screws.



Joey
ecohammer

Badger,
We notch back rafter tails and gable end fly rafter supports all the time. If have a 10" panel and you want a 6" exposure, simply notch the spline back before you install it.

Justv started our install on sun the 10th. Im building on the rafter tails and gable end overhangs next week. I had insulspan double the depth of the subfacia relief from 1.5 inch to three inch so we can build a ladder on the ground and mount it to the subfacia and sheathing. Ill send some photos next week after its done. First picture is jan 9 pm next is jan 3 pm. Stressful week, but awesome!

pics

If you are using 'attic roof trusses' and they are going to bear on the the top of your SIP wall, then the truss tails can overhang the wall to create your exposed rafter tails and the roof SIPs would just sit on top of the trusses like super thick roof sheathing. You would have to insulate and sheath between the truss tails because there will be a gap between the wall and roof SIPs. It would look similar to what 'Eco-Hammer' has done in his photos except his are separate added peices and yours would be integral to the truss.

You choose the thickness of your roof panels based on the insulation value you need for your climate and also for spanning capability.

ps: Why use attic roof trusses with SIPs, when the SIPs create a cathedral space you can inhabit with just a ridge beam? If I was doing the exposed rafter tail look with SIPs, I would do what 'Eco-Hammer' did in his photos.

Brawler, NICE PROJECT!

I would prefer to have the rafter tails appear to be just under the sheathing, not have a 10" thick roof above them. As to your question about using trusses and a SIP roof; the house will be 26' x 42' with a 16' x 8' bump-out on the south elevation. I wasn't sure if the SIPs with a ridge beam would span the 26.'

Badger,

Oh I see, your house is a little more complex than what I was visualizing. Thanks for posting the drawings. Without knowing all the particulars of your project, you could still forgo the trusses if you used 'intermediate' beams along with a ridge beam, but I don't know if they would interfere with headroom and such. What you are envisioning solves the problem too.

If the rafter tails are just under the sheathing then 'Brawlers' method sounds best.

Badger. Just an FYI, you may, or may not, be aware that there is an R-Control SIP manufacturer about 20 miles up the road from you, in Smithfield. You can find their location and contact info on the
R-Control website.

Good luck with your project.