We're going to put traditional roof trusses on top of SIP wall in our new second storey.

We plan to use cantilever/energy heel trusses.  These have a better defined load/contact point.  For a scissor truss this load point should be on the inside of the SIP.  This allows the interior slope to start at the wall instead of on top of it or inside it.

Does anyone see a problem with this?  Is there any reason why it should be centered, on the outside, anywhere else?

Thanks

Stoncaveman;

The load should be shared by both the inside and outside skins so that the shear load is shared by both and not just one

Not sure what type of SIPs you are using, but the bearing for the truss would generally be the full width of the top plate. i.e. for a 8 1/4" SIP the bearing surface for the design of the truss would be 8 1/4", the full width of the cap plate on the wall. The connection of the cap plate and any locking plates to the SIP skin, and/or bearing of the cap plate onto the skin of the SIP looks after the load transfer. Just let your truss supplier know the width of the bearing surface and they will adjust the design accordingly.

Geordie

Thanks for the input. The SIPs are 8 1/4" OSB skinned. The design included a double top plate with the cap plate a ripped 2x10 on the top bearing on the OSB as well as the first 2x8 so there is some spreading of the load between the two skins. I'll go back go the truss supplier armed with your comments and see what they can do.

Thanks,