I am planning a small addition to a traditional stick-built, two-story house (about 25 years old).  The addition will be roughly 16'x16' outside dimensions, and will be two stories.  The existing house has vinyl siding, wood trim, and an asphalt shingle roof with truss framing.  The addition will need to match as closely as possible.

So the question is -- would it be masochistic to try to do the addition with SIPs instead of stick-built?  I've never built with SIPs before, so I would be hiring an experienced contractor to do the job, but I worry about the number of field cuts and shims that would be necessary to make it match up with the existing structure.  That will add labor costs, even if I'm not the one who has to deal with it.  I'm especially worried about how I'm going to make the roof framing work -- it's not easy to make modifications to a truss-framed roof.  I don't think that's going to be any different with SIPs, though.

Let us know the area that you plan to build in and someone should be able to recommend a SIP company near to you that would take a look at your project and answer all those questions.

I'm near Raleigh, NC.  But -- I don't want a general contractor or builder, because I can't afford the 20-25% markup.  I intend to draw the plans myself with the assistance of an engineer, hire and manage the subs myself, and in fact I'm going to do the interior work (electrical, drywall, trim) with my own hands to save money, since I know how to do those things.  The key sub that I need is a carpentry crew that has built with SIPs before, to get me as far as dry in.  I can take it from there.

I know of one manufacturer in NC so far: Eco-Panels (http://www.eco-panels.com/), though I'm sure there are others not too far off.  I like Eco-Panels because they use polyurethane foam, which I think is my preference.  They also have a clever pre-assembled corner panel that looks quite nice -- anybody used their stuff before?

But I guess I'm not completely crazy thinking I can do an addition to a stick-built house using SIPs?  Ideally I would do walls and roof with SIPs.  I think it makes the most sense to do the floor with traditional framing and plywood or OSB subfloor.

Think about it. What is different from a stand-alone SIP structure and an addition? Basically, it's where the two connect. And, that is not usually a big deal. It all depends on condition of the existing house(plumb, level, etc.). That is where you msy need manual corrections.

Don't fall in love with those premade corners, they are 'fluff'. The real question is how easy is it to field adjust panels? If someone tries to tell you that it never needs to be done...They are lying.

Plumb?  Level?  That's exactly the problem.  The house I'm adding on to was not exactly built to exacting precision, and on top of that the foundation was done badly and everything has settled.  (Foundation is being stabilized and jacked with piers as part of this work, but that's unlikely to really bring everything back to perfectly square.)

So field adjustments are going to be absolutely necessary if I do this.  That's what worries me a little -- the additional labor costs of doing it, plus the reduction in efficiency and strength of the SIP system because of the little adjustments, shims, whatever.  I suppose I can just foam up whatever gaps there are, and it should be OK.  But if I try to butt a SIP roof up against the existing roof, and the existing roof isn't on exactly the slope it's supposed to be on, there could be some big gaps to fill.

Maybe I'm over-thinking this.  As I said, I've never done anything with SIPs before, so maybe the field adjustments are easier and better than I fear.

mortman,

I've never built with SIPs, but I've been reading in anticipation of building my retirement house.  I had a marked preference for factory cut panels, but a recent thread made some strong points in favor of site cutting -- one of those points was the ability to to adjust for site conditions. 

http://www.greenbuildingtalk.com/Forums/tabid/53/forumid/5/tpage/1/view/Topic/postid/37092/Default.aspx

Good luck,
Larry