I'm really torn about SIPS. Why would I wrap a 500 year (potential) frame with a 50 year wrap? (Correct me if I'm wrong, but don't all glued boards degrade pretty quickly if wetted?)
Also, SIP's are supposedly stand alone for structure. It is NOT elegant to design a stand-alone structure, with another stand-alone structure wrapping it.
Am I missing something?

I do not know anything about the lifespan of SIP's but 50 years sounds about right. I have never used them and if I can help it never will.
It is certainly a quick and easy way to enclose a frame. And for most frames I have seen they are also necessary since I doubt that a 4' knee brace on a 8' or longer post is hardly enough to stiffen any timber frame sufficiently.
Why are they being used instead of proven methods hundreds of years ago? My guess is the cost and speed of assembling a frame/house. It also protects the frame as compared to a German style frame with exposed timbers which needs some care to maintain its beauty.

As to glue degrading when getting wet. Why or how would the panels get wet after installation and being covered with exterior wall covering? If built right they should never get wet other than under occasional high humidity levels. But then they will dry out again. That is if the installation was done correctly.

SIPs for TF enclosures typically lack the same amount of structrual elements. They will have significantly more plywood splines and less dimensional lumber. We pay about 1.00 per sq. ft less for the SIPS used on TF vs the strucural SIPS.

As far as the OSB getting wet is concerned. Thats more a problem of building practices. There isn't a good reason why SIPS or any wall structure should get wet from external sources. My guess is.. It will last at least as long a traditional 2x6 wall with the exact same OSB exterior sheathing.

More than likely if they were installed correctly they will last longer since they are less likely experience the same types of leaks and condensation/melting frost running down the inside of the OSB of a traditional wall.

At the end of the day... there are only two kinds of SIPS. The ones that got installed right and the ones that didn't.

Pegs_1,

does not SIP stabd for structual insulating panel? How can there be one that is not structual and one that is?
Like I said I have never used them but since you brought it up I had to ask.
I agree with you otherwise.

Enrico

I was having lunch with some timber framing students and an very experienced timber framing contractor who as been building frames for 20 years or more. A student asked him about brace placement and how many braces should be in a frame.
His reply was that every rectangle, in the frame, should have two opposing braces. That's why you see things like this in old buildings:



Next, we need to discuss terms, if a panel isn't structural then it is not called a SIP. SIP stands for Structural Insulated Panel. If a panel isn't structural then it's called something else.
Some clarification of terms or the proper use of terms helps everyone understand, what is what.
A panel that has sheet rock on one side and then foam and then osb is a "curtain wall" panel, according to my supplier.
A SIP is called a sip because it is a Structural Insulated Panel.....
A curtain wall panel is not a structural panel, but it is an insulated panel.
And these terms may change from one supplier to another, so we need to be careful about what we call panels that are not structural.

Jim Rogers

EH,

How do you enclose (or infill) and insulate your timber frames?

As for the SIPs, I hope they last longer than 50 years. (but I'm not saying they will - how can we know?) I decided not to use plywood or SIPs in my roof system because I just didn't feel that either, in that particular service, could outlast the slate above it or the timbers beneath it. As for my walls, the SIPs with prefinished window openings and electrical boxes were just too tempting to pass up (and I was resigned to some sort of sheathing to get the added stiffness). It went fast, but screwing the SIPs to the frame felt like taking a magic-marker to an oil painting.

20% of my house walls are infill (sans SIPs). That's why I am so keen to learn more about the way you do it EH.

-Thomas

BTW,

When we put the SIPs on my house, the installation procedure required nailing a 2x3 bottom plate around the house (cantilevered somewhat beyond the foundation), over which a grove in the bottom of the SIPs slid. The mfg'ing tolerances of the SIPs (and the pre-existing roof overhang in places) made fitting the SIPs over the supplied 2x3's somewhat trying at times. The guys helping me asked if we really needed that 2x3 btm plate, since the SIPs were also being screwed on 6" centers to the side of my 8x8 timber bottom plate. In our application, the 2x3 was clearly redundant, but I said "yeah, we absolutely need that 2x3, it's there to keep the insulation from sliding out after the OSB rots."

-Thomas

Jim,

that's what I was saying with only two braces between each bend at 8' height or more. This would not be sufficient for me. Yet, I see it all the time. So those frames must rely on the SIPs.

That Sips are what they are was clear to me but when pegs_1 brought up the structual and not structual SIP I had to ask.

Thomas,

check out the German Timberframe thread. I explained the wall detail there.

Enrico