Sure, just hang the joists from the top of the SIP walls.


That would depend on the complexity of your roof.

Right, but can I hang joists from the ceiling of the SIP roof? The attic floor would be up in the cathedral ceiling created by the SIPs roof, not at the height of the walls.

we typically balloon frame the walls and hang from inside of wall panel

I was afraid that is what you were really asking. %^) It would definitely have to be engineered. You could connect your ledger to the splines and/or the skin. Bill Chaleff has written about just using a tight fastener schedule and attaching to the skin. Look the article up, it's in the learning center. And, you could also have 2x material embedded in the panel, and connect to that. Either way I'd say it's probably doable(but I'm not an engineer!)

Not an engineer either, but it seems like it would be too much of a concentrated load and as others have pointed out  - not all OSB mfgs. use 2x splines. The skins have a limit before the will delaminate, I would never rely on skins to support floor load and pull out values in OSB are poor.
If you transfer the load to the walls like normal, it would not be a problem.

It sounds like you want to 'hang' a floor system from underneath your roof panels. Are you thinking about 'living space' or just storage? If you thinking living space, I don't think it would work. Even if you upsized the panels, and added the required 2x splines to carry the loads. You still have the problem of how do you attach this floor system to the roof panels. I think the critical load points here are the mechanical attachments (screws?), not the load capacity of the roof panels. This does NOT sound like a good idea to me.

Hmmm, but they could if they desired. And, I wasn't talking about 2x.


Would they be better with steel? And, can steel SIP manufacturers embed structural members within the panels?

I also agree with Wes. It doesn't sound like a good idea, but I'm on the side that it can be done.

Non-living space. Probably not even storage. Just running HVAC and electrical. Effectively it's just a drop ceiling to bring the height of the room down a bit. Sounds like I'm probably better off using trusses and framing with SIPs panels on top?  That's the direction I was leaning anyways, relying on the OSB skin to carry any sort of load doesn't sit well with me.

If you are using this idea strictly as a way to hide mechanicals, lower the ceiling, AND you have some type of structural spline elements (2x's, i-joists, etc.) at 4-8' on center, then I would have no problem with hanging it from the roof panels. But 1/2" OSB just doesn't have enough 'meat' to carry the loads.

Makes sense.  Anyone know of any PU SIP manufacturers that use structural splines?

AC Tech uses structural stiffeners in every 2' wide panel.

JC;

 

you may think my motives are obvious, but you are wrong and no our steel panels are not designed to hang a concentrated load from the ceiling
if you read the earlier post istated that we hang from balloon framed walls

For what's worth, I went with traditional roof trusses and dropped my panels (8.5") on top.  Talk about a strong roof.  The attic area is used for storage.  Two things.  I needed a crane to get my panels up.  Also, hitting a 1.5" wide truss with a 10" screw through an 8.5" panel was, um, intersting.

EPS panels I assume?  The PU roof panels I've seen are around 6" thick, still probably no easy feat hitting the truss!

EPS indeed.  Many frustrating holes drilled and filled.  Since I built this house myself along with a few friends, I was more comfortable having the truss engineers design to code the truss system.  Not only that, there was no need in my plans for a cathedral ceiling.  I did have them design (and I installed) a "tray" ceiling in the master bedroom.

I am also concidering sips to replace an existing roof , cathedral ceilings. Is it possible to have the panels come with finished with tongue and groove wood, over the plywood for the inside ceiling?

danashouse,
don't know of anybody who makes panels with t&g 1x's. However, 4x8 panels with T-1-11 wood siding in lieu of osb is easily done and makes a really nice looking ceiling.

Insulspan is a company that has applied 1 x T & G over the skins of the panels and shipped them out that way. It never made sense to me that 4 foot wide panels would have T & G applied to them before hand. Seems it would cause issues with the set and then you'd have to run batts to cover all the seams, which is not what you want to do to with a T & G ceiling. Now what we have done, is to pre-assemble roof sections on the ground and apply finishes to it and set the entire roof section. Works out real slick. The biggest roof sections we've done like that have been 20 feet wide and a diagonal length of 20 feet ( 22 ft with the overhang ). Saved a bunch of money at the finish.

The Panel Guy