I've been thinking alot about alternatives to SIPS and wondering one thing: when the topic of build-in-place exterior (to the frame) enclosures (i.e. 2x4 or x6 walls with sprayed foam or cellulose) is discussed, why is the spacing always so close? We all don't want our frames made redundant.

Am I missing something? Couldn't we build these frameworks minimally -- frame in windows and doors, add enough for sheathing (4' centers) attach it to the frame for stability, and insulate that? Reduce conductivity, reduce redundancy?

thanks,
matt

I had a frustrating experience where the structural engineer for one of my frames insisted on 12" spacing on the exterior framing (2x6) to meet lateral loading requirements. Like you, I was hoping to keep the stick framing to a minimum to avoid redunancy. The engineer insisted that the 18 knee braces in this 1.5 story, 1000 sq. ft. cabin could not be considered as providing lateral restraint.

I would be interested in knowing how the stick built wall is tied to the frame itself...
Why not at least 2' on center? it would reduce the # of studs, reduce conduction and cost. If you put horizontal strapping on the inside the foam insulation would effectively wrap the studs futher reducing conduction..
Just a humble thought from someone who thinks there has got to be another alternative to sips......

I've fastened stick framing to timberframing with 8" or 10" nails, predrilling helps keep the splitting down to a dull roar,then get out the small sledge hammer, and send the nails straight through the edge of the stud.
I think more than 2ft centers will not support drywall well enough. Also 18 braces for 1000 sq ft and 1.5 storey sounds light to me. I'd think more like 30 or 40(I built a 1.5 storey at 864 sq ft with 48 braces), but then I tend to over-build...
what's the diff between spray foam and sips, anyways?

2x6 24" OC is common practice in stick framing for 1 story structures. 24" provides adequate sheet rock and plywood backing while keeping heat transfer to a minimum.
I have never encountered a 12” spacing for lateral. Usually these problems can be solved with a tighter nailing schedule on the same centers and/or thicker sheathing.
If I were enclosing a frame with stick building I would want to avoid redundant framing, specifically load bearing elements. I would include some typical frame details showing openings with minimal framing (light headers, no trimmers) in the constuction docs so as to get approval from the plan checkers before building and (theoreticaly)avoid debates with the building inspector.
These details could be worked out with the engineer whom you have probably hired to calc the frame. If the stick frame is to impart lateral to the timber frame then the engineer would have input on that attachment as well.

I just finished a 5200 sf P&B colonial with a high-post stick-built barn attached. We framed 17ft 2x6 curtain walls for the colonial frame and used come-a-longs from a second floor joist to haul them up. It went very well. We did go 16" on center because we didn't use sheathing. We applied 2" EPS foam to the exterior and then screwed vertical strapping as a nail-base for CVG 6' spruce clapsboards. We used BIB fiberglass system because it was less than BIB cellulose. With the 2" foam on the exterior, no wind migrated inside the wall cavities. We did a blower-door test on the place when we finished and it pass with flying colors. It was a very very easy place to heat this winter while we finished the interior. They're expecting to heat with 2-4 cords per year! We packed-out the P&B frame with 3/4" pine spacers so that we could easily slide sheetrock behind timbers. We prewrapped these timbers with poly scraps before we applied the pine spacers. We just toenailed the 2x6 studs at the second floor line with 16pgalv nails and used timberlocks at the top plate. We used local materials, changed window locations twice, no formaldehyde, and probably less than the $7 per sq ft panels cost. Plus we got our drainage plane behind the claps!

I'm running the numbers for enclosing a 2000 sq ft structure. I've got no end of 1 inch white pine T & G rendered out of the logs that gave us the timbers. I'd like to lay it diagonally across rafters on 36 inch centers, for aesthetic and stiffening effects. Is there any killer reason not to put a thick nailbase EPS panel (OSB on top side only) on top of that, and then apply roofing. What TYVEK, vapor barrier, roofing felt, etc. is recommended? Would more expensive polyisourethane sandwich panels be worth the cost?

S. Bingham:
Consult your panel company about nail base panel attachment needs. It could work.....
Depending on your roofing material specs you may be able to apply over felt over nail base.
If this complys with roofing shingle warranties that's good, if not you may have to build up a "cold roof" with a spacer and another layer of osb or some other sheet material and then create the roof.
You'll have to pick a panel company and get some details directly from them....
Good luck with your project.

Jim Rogers

On stud spacing, it is not unheard of to specify close spacing to ensure adequate stiffness normal to the plane of the building, where there are very high wind loads. This is for wind against the face of the wall, not for shear loading, (which is what tighter nailing helps).

Joe