I have ICF foundation and gigacrete EPS panels for the main floor. Ideally I should have had floor trusses hanging on the inside of ICF and set Gigapanels on top of the ICF wall. I cheapened out and decided to set the floor trusses on top of ICF(gigapanels will sit on the trusses). Anyway, I will have the trusses sit 3 1/2" from the outside of the ICF foam. There will be 1/2" sheathing on the trusses and then 3" EPS which will be flush with ICF and Gigapanels. My question is what would be the best option(for moisture management) to sheath the floor trusses? What would be the pros and cons to the following? ZIP DOW SIS exterior gypsum OSB/ply I also have some gables and the same question applies to that as well. Thanks

Anyone?

Ok maybe I am not asking my question the right way.

How about opinions on rim assembly details?

1/2" SIS sheathing with 3" of EPS foam on the outside?

Also, what would be optimal insulation on the inside of the rim board with the above assembly?

Dana? anyone?

Is 1/2" SIS sheathing sufficient for the floor truss rim board from a structural standpoint? Is it approved for this application? What is the depth and on center spacing of the floor trusses? What load will be imposed on the end of the floor trusses by the walls and roof assembly? What type of floor decking will be used?

I didn't know what a gigapanel is until I googled it. After googling it, it appears to be an EPS panel with steel studs every 2'. Can the outer 3" of the panel be unsupported as in your scenario where it is over 3" EPS attached to the rim board? It doesn't look like it can to me. The wall I saw on their website showed what appeared to be 3.5" wide steel stud with ~1" of foam on either side for an approximate overall wall thickness of 5.5". What you have proposed above would result in less than half of the steel stud being supported by the trusses and rim board. This would not be structurally sound because this point is not only supporting the wall, but also the roof and associated loads (get any snow where you are building?). The only way I could see this working is if you set the outside edge of the steel studs flush with the outside of the truss rim board and then attach additional layers of EPS foam to bring the outside of the wall flush with your ICF foam.

Arkie, Thanks for the reply. I forgot to mention that I am going with 8" EPS panels with 3" being on the outside. So the steel tracks sit on the trusses flush with the outside of the rim board. Floor trusses are 20" deep at 19.2" OC. Also these have ribbon notches to accept 2x4 "ribbon board" which is the structural element. The sheathing material for rim board doesn't have to be structural in this case.