SIP Panel Layout for a Roof

I am having an old barn frame moved and rebuilt as living space this summer. We will be doing a lot of the work ourselves.

For the roof we are planning to do SIP panels to get the required R-38. However, I am not sure of the panel orientation.

The barn is an English style with principle rafters spaced about 12 ft apart. Purlins run about 4 feet apart with vertical sheathing.

We plan to re-use the sheathing as the visible ceiling under the SIPs. These boards will have to be installed from above before putting down the SIPs. This means we won't easy have access to the lower spine joints on the SIPs.

We could run panels from ridge to eave, about 20 ft, but then the middle panels would only be resting on the purlins.

Or we could run panels horizontal and put the butt joints on the rafters (using 12 foot panels) and line the long edges up over the purlins (using a mix of 4 and 8 ft wide panels).

Any thoughts or other ideas?

I have read a little about the "wrap and strap" ideas, which I am planning to use for walls (in part because we will have a lot of small windows). However the added strength o the SIPs on the roofs seems to be worth it.

Thanks.

I would discuss your ideas with your panel company supplier. He may have some suggestions of what will work for you.

Jim Rogers

Personally I would want to install it with panels landing horizontally. If you can do it with 4x12 panels thats a large enough panel. Anything bigger gets harder to slide into place even with a crane. The sip company should have an engineer that can stamp it. He should be best able to tell you the possible orientations.