I'm in the planning stage for a project and am considering using SIPS to reduce my build time. I've got a preliminary sketch of a 4/12 roof and I am wondering if if SIPS manufacturers could produce this roof? The suite above is meant to be a 7' wall (also SIPS) with a vaulted ceiling to give the interior more headroom. I could easily stick frame it but I want to reduce the overall build time and increase the r-value of the structure without lowering the interior ceiling. Can SIPS be used with out a truss system in this design?

BooUrns;

Yes, we have done many complicated roof systems and having built over 90 SIP homes and commercial buildings, have never used trusses.
SIPS mfg.s can produce it, but we prefer to field cut and install to allow for foundation conditions and errors.

Boo,
Your design is only a problem if you reject all notion of any load paths in the form of posts or beams. If interior support elements can accommodate the many(ten) different point loads, the roof is a relatively straight forward SIP roof. I personally don't agree with Mr Kavala about site cutting. You said you wanted to reduce your build time and site cutting will seldom do that. In fact using 3D design combined with CNC fabrication is the best way to ensure that complex roofs go up quickly and fit together properly. Good luck,
Al Cobb

Al;

I don't have a problem with the CNC fabrication, the jobs I have seen done are excellent. Provided the foundation is perfect, therein lies the problem.

I recently consulted on a Sure tight project and was impressed with the precission

If I may, the CNC fabrication was done on my roof (not as complicated but still...). The panels were spot on, however, Chris makes a great point about all the other factors in building. I would suggest that using SIPs for the walls would speed up the build process but it would slow down (rightfully so) to get the roof just right. BTW, that is pretty cool lookin'

Thanks for the replies.

I would prefer to go with a contractor that can produce the upper structure in shop and deliver to site ready for assembly. I wasn't sure if SIPS could be used in this type of application without a truss support as most of the SIPS roofs I've seen were straight runs.

Now to find some local manufacturers for pricing.

BooUrns,

I would build the main body of the roof upper roof out of SIPs and stick frame the smaller sections of the upper roof as "cosmetic" overlays. If you want the cross vaults, the support framing alone will be very complicated and time consuming to build not to mention the panel installation. the lower level roof is not a problem.

That's how I figured it would work out as well. I want a cold roof on top of the SIPS so I would have ended the panels at the wall line on the main roof (only the furthest bump out would require an additional section). I would add the soffits on while integrating the cold roof lattice.

I'll run it by an architect I know and then goto the city for development permits.

Thanks for the input guys.

BooUrns,
Anything can be done, but is it practical. For a roof like this you will definetly want to have a structural engineer do some loading, Architects are not engineers and would most likely not know the answers. I am neither an Architect or an Engineer, but a builder that has built many SIP's roofs, some more complicate than others. While I am a huge advocate for SIP's, I might consider conventional framing with a closed cell polyiso insulation sparyed insulation. Pretty costly stuff here in MA, cost around $1 bd/ft or $6 sq/ft for 6" of foam R-36 depending on who you talk to. I used this for one section of the house I just finished building. I was concerned that I would have thermal bridging occuring through the framing members, but when shot with an IR camera I was pleasantly surprised to find none and I mean none. I couldn't believe that there wasn't any but the IR camera doesn't lie. SIP's on the other hand, do have thermal briging issues at the seams, especially if you are using an solid wood splines, if done, over purlings or beams this is not the case.
As for site cutting the panels, for me this is counter intuitive. The main reason I like SIP's are the reduced time, waste and mess on the job. Sometimes you have no choice but to cut them on site, but this is typically the result of a change or mistake in the framing below.
So the answer is YES this can be done, but the question remains is this the best, most cost effective approach? By the time you are done adding all of the structural elements needed for the SIPs and installing them, I don't believe you will have saved any time. Two days for either roof with a good framing crew or a good SIP's installer. The only difference is you won't have to go back and insulate. Spray foam insulation is a dirty job and definetly left to the professionals.

Tom Pittsley
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www.eebt.org