Posted By ReadyToRetire on 11/18/2007 8:31 AM
All,

When I thought of SIPs, I envisioned OSB clad panels.  Having worked with wood, the problems were fairly evident, but they seemed to be significantly outweighed by the advantages.  Thanks to this forum I'm now aware of steel clad SIPs, but I have no experience working with sheetmetal, so problems and solutions are far less obvious.

I've bought and read Morley's book, which discusses OSB/SIP construction.  But I've not found a similar book for Steel/SIP construction.  Is there one?  Has anyone compiled a realistic list comparing OSB and steel skin SIP techniques for residential or small commercial construction?No one has done one yet, but unlike OSB all steel SIPs are not created equal or generic, they come in a variety of widths 24" to 48" and a vary in available lengths. The interlocks are all different, some companies pay royalties to others for patent infrigements on the interlocks. Some require the seams to be stitch screwed together others are ingineered without joint fastening.
So it would be difficult to make a "standardized" manual when there are so many variables. Most OSB panels are generic, ther a few that have some uniqueness to themselves

If it matters, I am considering building in the Eastern half of Virginia where the heat load exceeds the cooling load but without the real cold of the Northern states.  And there are humid summers with rain -- but not to the extent that the South-Eastern states have.  I live in Northern Virginia and have had minor problems with termites, carpenter ants, and carpenter bees, and significant, but not major, problems with humidity based rot in plywood soffits.  So steel has a *real* attraction.


My questions:

Thermal bridging at edge caps:  During the summer, this would be a seemingly minor efficiency issue.  But, during the winter, it could lead to condensation on each door or window penetration similar to that along Aluminum window frames. 

My rule of thumb is, if you are north of the Mason - Dixon Line then you should start using thermally broken base, top & window/door buck channels
Does this limit how far North steel skins are practical?

No, ther are no limitations, many steel sips houses have been built in Calgary and other parts of Canada

Is there an accepted solution that's not too unsightly?

There is no change in the appearance of the structure

Fondation connections:  The construcion technique for OSB SIPs seems to naturally form a layered water barrier -- a 2x plate that is straddled by the skins to form a lap on the outter surface.  My understanding is that the 2x plate is replaced by a steel channel into which the SIPs are placed. 
When water gets beyond the siding, it would seem to naturally pool in that channel with no way to dry.  Why is that not a problem? 
Channels have weep holes to let out any moisture if it gets in 
Do I need a house wrap just for that joint?
It is not neccessary , you could seal the joints with a self stick tape if you wanted .
Does the channel have an even greater need for a flat and level foundation than a plate?
No, we get some pretty ugly slabs in Florida, we simply use a self expanding foam under the channel - this will float out any irregularities.

What fasteners are used and is any unusual tooling required?

Fasteners:
For plate anchoring - wedge anchors or wedge bolts
For panel to channel attachment - #10 x 3/4" tek screws
For roof attachment  - Trufast HD and LD SIP screws, with washer

Tooling:

A Refrig Panel saw is recommended, blades are cheap about $5.00 each
Magnetic level
cordless and corded drills
magnetic hex driver

If you are building more than one we would reccomend a Muro automatic feed gun with strip screws, It will pay for its self in 2 jobs


Connections between panels:  My understanding is that the steel skinned panels that fit together forming an inner and outer lapped joint at the skins and a tapered, mating joint in the foam.   
Is the joint slid together or snapped together?
That varies with the MFg. ours are a friction fit, others have a snap connection, others are screwed together.
The joint would seem strong in tension, but how does it do in compression:  Does a steel/SIP wall withstand racking as well as a nailed, spline-joined OSB/SIP would?
I have not compared the racking test of one against another, I can tell you that with the 3 different steel SIP companies I have used, they all have tested out at triple the strength of wood framed walls, they all can be used as shear walls. We can e-mail you the test data including impact testing 
OSB skins, with their nailed splines, allow forming door and window openings by inserting partial panels.  Without the nails to hold it in place, what keeps a steel skinned, partial panel from sliding down?
We normally don't insert partial panels, unless the window/door is too large, in that case we would place one screw at the top seam to hold in position until - the next panel is installed and the openig channels installed

Mounting cabinets:  OSB skins allow an easy to understand solution of scabbing on a 1/2" ply or OSB sheet instead of drywall where the cabinets will mount.  How are cabinets mounted onto steel skins?
A 4" x 18 ga. flat stap - stitch screwed to either steel skin or furring  ( these are available at any metal stud supplier)

Dry walling:  A real side benefit to OSB SIPs seems to be not worrying about hitting studs with DW screws -- you hit OSB no matter where you shoot.  Steel skins seemed to suffer a corresponding problem with having to fir out to allow electrical service because there were no chases in the panels.  But, in a recent thread, Chris Kavala noted that you could mount drywall directly to the steel skin in areas where you didn't need to run wiring. 
What screws are necessary to mount DW on a steel skin?
Same as a wood drywall screw
Are they available for a auto feed driver?Yes

Electrical wiring:  A tall base molding with an internal chase and outlets in that molding (and no switches in those wall sections) would seem to eliminate the need to fir out. You could do that but, most people like the conventional placement.
But to wire an OSB house, electricians have likened it to doing a remodeling job, needing to use cut-in boxes and fishing wires. This difficulty has driven up the cost of electrical, we have had a few electrical inpectors not like the fact that the wires were concealed
 But:
How do you wire the doorbell?
You are correct, but the chase also provides aconvienent chase for 1/2" water pipes on an exterior wall, that can be problematic with OSB

Isn't is also much easier to fish wire thru a 1-1/2" air space to add a recetacle later than thru a solid OSB wall?
Is there an accepted way to mount and wire the internal switches for outside lights? Use a surface mouted pancake box attached to skin and back feed wires to fixture from interior chase

Can household wiring be run within the door opening and surround?  (Would it meet code?  If so, then I could add a small key shelf with a thicker base, mount the switching and chase in it, and mate it to the door molding.)

Could be done that way, but not sure it would meet code. I prefer to do what we know will work

How do you mount and wire the exterior, wall mounted lights without a chase?  You have a chase on the inside and wires are fed to the backside of the fixtures

Sorry if they're dumb questions, but I don't yet understand the process.
Thank you for any comments and for any references that you can recommend.

Very respectfully,
Larry

Posted By Jelly on 11/18/2007 8:47 AM
I'll tag on and ask another possibly naive question. To mount siding or stucco on the exterior, or shingles on the roof, the steel skin is pierced with screws.
Wouldn't this leave hundreds of spots for moisture to enter the wall (or roof)?.
 Yes, just like nails in a conventional home pierce the barrier and wood, I don't believe that this would allow moiture to get behind the skin, if it did it would be even more catastrophic behind an OSB skin, wouldn't it?
If the foam inside then acts like a drainage plane, taking the moisture down to the bottom of the panel, then how does it get out?The foam is not the drainage plane, the steel skin is , as a precaution, weep holes are put in the base in case moisture would get in somehow

Posted By JohnCujie on 11/18/2007 10:49 AM
I agree that it would be good to have a source, other than the generous Mr. Kavala, to answer basic questions.  I think most questions have to do with interface with the other trades, not solely with the panels. 

Some from me.  What depth firring is used for wiring? 
1-1/2"
Can the skins be pierced for a 2 1/2" deep electrical box?
They can be, but by using the 1-1/2" strips you can fasten a standard 4" square x 1-1/2" box with a 1/2" plaster ring directly to the skin

I assume all boxes on the metal are metal. 
metal is a better for grounding  but plastic is perfectly acceptable and avialable as well in the 4 sq. box
  Is all the wiring in cable? 
it can be, but romex meets the code, even in commercial work
 Regarding exterior stucco:  Can foam for synthetic stucco be stapled on?
No, but screw attachment is common
 If conventional three coat stucco is used, how are paper and wire attached? 
Waver head screws are used and is code accepted

 I know that interior wood trim can be shot onto light gauge metal studs.  Is this also true for this product?
That correct, a standard pnuematic trim nailer will pierce light gage framing 

John

I e-mailed Metals, USA with some basic questions about their product SIPbloc since their website had no mention of it.  One question was could they supply it to my area.  Got a reply from a marketing rep that they would have to research and get back to me.  Doesn't give you much confidence. Do they even manufacture it, or just sell someone else's product?
RE: Metals USA, it is my understanding Metals Usa is no longer producing their panels for  residential use.It is also my understanding that they have scaled back production to just aluminum skin panels for patio use only

Posted By ReadyToRetire on 11/18/2007 12:15 PMI viewed OSB SIPs as interchangeable units from vendors of varying quality and support; I'd misapplied that simple model to steel SIPs.

Posted By ReadyToRetire on 11/18/2007 12:15 PM
Chris,

Thank you for your typically useful answers.

I viewed OSB SIPs as interchangeable units from vendors of varying quality and support; I'd misapplied that simple model to steel SIPs.  And it's good to know that thermal breaks are available -- that would solve the issue on the edge caps.  

Having been bitten more than once, I've become a believer in the KISS principle -- which is one of the advantages that I see in SIPs:  they markedly simplify the shell structure.  So it would be nice to avoid the complexity (as well as the material and labor costs) to build out the chase over the entire surface; but I can understand that it is a trade-off for increased labor and materials in wiring along the external shell.  My wife and I have seen and like the looks of bases with outlets in them, so, for us, that's not a problem. There is no depth behind the base for the outlet or wire? I can see that the OSB approach with set horizontal and vertical chases might not translate well to steel skins.  But:

Are internal chases available as an option -- for example for switches by entry doors?No they are not available on anything I have used

Are there reasons NOT to cut a chase into the core of a steel-skinned SIP? The manufacturing process with steel is different and not practical to do that 

Would there be a structural or durability issue with cutting a vertical chase into the core,No
 cutting a horizontal chase to the edge and across the header section,Yes, your header wether steel or OSB would be compromise if you were cutting the skin to put in the chase installing penetrations from the outside to those chases, cutting an opening the size of a switch box (assuming that it's 5-6 inches from the door opening), and fishing that short stretch?  (It sounds like a lot of cutting, but it would all be internal except for the penitrations at the lamps (which are needed anyway) and the hole for the switch box.)There is no problem with cutting in as many boxes as you want, even close to the door

VERY respectfully,
Larry