How To Attach Roof SIPS to ICF walls
Last Post 16 Dec 2011 06:08 PM by cmkavala. 21 Replies.
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LbearUser is Offline
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06 Dec 2011 11:16 PM
I am trying to find some info on how a SIPs roof would attach to an ICF wall. Also, how hurricane/tornado proof are SIPs?

Being that truss style roofs utilize a "hurricane strap", what does a SIPs roof offer?

Lastly, is it true that a 12" foam SIPs for a roof is R-58?
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07 Dec 2011 08:29 AM
ICF walls and a SIP roof is the ultimate. Your typical hurricane tie only has a hold down strength of 200-500#, and the last couple ICF houses we used Simpson Strong-Tie LTA2s with a hold down of 1210#.

What insulation does the SIP have, if it has the typical EPS foam it would be closer to 48 for an R-value. EPS is what I would use.
Brad Kvanbek - ICFconstruction.net
JellyUser is Offline
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07 Dec 2011 10:54 AM
So would you anchor a pressure treated plate to the concrete in the top of the ICF wall, and then through-screw the SIP panel in place?
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07 Dec 2011 01:34 PM
With the LTA2s there is no plate, they embed into the concrete. LTAs are made for trusses, but I would think they or something other Simpson or USP connector would adapt to SIPS.
Brad Kvanbek - ICFconstruction.net
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07 Dec 2011 06:59 PM
Posted By ICFconstruction on 07 Dec 2011 08:29 AM
ICF walls and a SIP roof is the ultimate. Your typical hurricane tie only has a hold down strength of 200-500#, and the last couple ICF houses we used Simpson Strong-Tie LTA2s with a hold down of 1210#.

What insulation does the SIP have, if it has the typical EPS foam it would be closer to 48 for an R-value. EPS is what I would use.

With a SIP roof, I am wondering how the LTA2 would be secured to the SIP roof. Since all you have is 12" foam and 7/16" OSB. That is not enough "meat" or strength there to nail or screw to. The foam portion is basically zero when it comes to pull out strength, not enough OSB there to prevent pull-out.

Am I missing something?
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07 Dec 2011 07:46 PM
It would depend on the SIP manufacturer but they do or could install splines to attach a LTA2 or another embed hold down. Or are the SIPs going over trusses? this is where a SIP guy should way in.
Brad Kvanbek - ICFconstruction.net
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08 Dec 2011 09:43 AM
Yes surely a pro will weigh in, and one of them may even post a detail illustrating it for you. But I know one way it's done with steel SIPs is akin to what I described with the PT plate. Can't see why it would be different with OSB panels.
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08 Dec 2011 01:41 PM
Posted By Lbear on 06 Dec 2011 11:16 PM
I am trying to find some info on how a SIPs roof would attach to an ICF wall.

Being that truss style roofs utilize a "hurricane strap", what does a SIPs roof offer?

Typically what I have seen is that long screws with large heads or washers, i.e. SIP screws, are screwed completely through the SIP into a 2x wood plate that is anchored to the top of the ICF wall.  The wood plate is shimmed as needed to match the roof pitch.

http://www.r-control.com/downloads/...Screws.pdf

http://www.trufast.com/products/sip_nail/index.html

This link shows a detail for what I described above:

http://www.greenbuildingtalk.com/Fo...fault.aspx


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08 Dec 2011 01:53 PM
Posted By Lbear on 06 Dec 2011 11:16 PM

Lastly, is it true that a 12" foam SIPs for a roof is R-58?

A 12" SIP using the standard EPS foam core and OSB skins will be ~R45 @ 75F.  That's 11" of EPS at R4/inch plus ~R0.5 for each of the OSB skins.

I have seen claims of R53 for a 12" SIP using NEOPOR graphite added EPS foam from one manufacturer.

To get a higher R value than that will likely require the use of Polyiso foam which has an aged R value of ~6.0 per inch.  I'm not even sure if SIPS are made that thick with Polyiso.

BTW, Polyiso is short for polyisocyanurate
AltonUser is Offline
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08 Dec 2011 05:49 PM
It is more likely that a SIP with a 6" core of Polyurethane will have metal skins since this is common.
Residential Designer & Construction Technology Consultant -- E-mail: Alton at Auburn dot Edu, 334 826-3979
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08 Dec 2011 08:25 PM
Posted By arkie6 on 08 Dec 2011 01:41 PM
Typically what I have seen is that long screws with large heads or washers, i.e. SIP screws, are screwed completely through the SIP into a 2x wood plate that is anchored to the top of the ICF wall.  The wood plate is shimmed as needed to match the roof pitch.

http://www.r-control.com/downloads/...Screws.pdf

http://www.trufast.com/products/sip_nail/index.html

This link shows a detail for what I described above:

http://www.greenbuildingtalk.com/Fo...fault.aspx



What are the ratings on these SIP screws? Are they IBC accepted?

You would figure that the engineers who designed SIPs would have created a special bracket that would work when installing these roofs. It's almost as the attachments are an after-thought.


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08 Dec 2011 08:58 PM
Of course the screws are reviewed and specified by engineering, not an afterthought at all. A lot stronger than a hurricane strap - a truss roof on an ICF structure is the weakest link and a real pity when SIPs are available.

Simon, where you at? Give the man a detail drawing...
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10 Dec 2011 12:38 AM
Posted By Jelly on 08 Dec 2011 08:58 PM
Of course the screws are reviewed and specified by engineering, not an afterthought at all. A lot stronger than a hurricane strap - a truss roof on an ICF structure is the weakest link and a real pity when SIPs are available.

Simon, where you at? Give the man a detail drawing...

What about water intrusion due to the screws going through the roof into the foam and then into the ICF wall?

I just didn't think a thin screw like that would allow that much strength compared to a metal tie.
SimonDUser is Offline
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10 Dec 2011 01:15 AM

Ok Jelly, didn't want to leave you hanging.



SIP Fastener Design Criteria

Building Designer PANELfusion, LLC Tampa, FL simon@panelfusion.com "Metal SIP Advocate"
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10 Dec 2011 03:17 AM
Posted By SimonD on 10 Dec 2011 01:15 AM

Ok Jelly, didn't want to leave you hanging.

SIP Fastener Design Criteria



Thanks Simon!

1-So with the above setup, one would meet 140MPH wind/hurricane codes?
2-From what I read, it appears that these screws are needed every 6" OC?
3-How does one make sure that the screw is at the proper angle? (It appears that any deviation from the exact angle would make the screw miss the top plate.)
4-The ICF has to be poured and shaped at a certain angle in order for the SIP to lay across the ICF wall properly. How does one figure the angle and when is it created, during the pour or after?
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10 Dec 2011 08:33 AM
Lbear,

Please note that the top plate was sliced instead of sloping the top of the ICF wall as you and I have been discussing.  Sloping the top of the ICF wall eliminates the need to slice the top plate.  A hat channel properly insulated should be able to replace slicing the top plate.
Residential Designer & Construction Technology Consultant -- E-mail: Alton at Auburn dot Edu, 334 826-3979
LbearUser is Offline
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10 Dec 2011 03:13 PM
Posted By Alton on 10 Dec 2011 08:33 AM
Lbear,

Please note that the top plate was sliced instead of sloping the top of the ICF wall as you and I have been discussing.  Sloping the top of the ICF wall eliminates the need to slice the top plate.  A hat channel properly insulated should be able to replace slicing the top plate.
With slicing the top plate like that, I assume that you lose quite a bit of strength. That 4x8 became a 2x8 when it was sliced like that.


Plus, what are the chances that the SIP screw will hit that J-Bolt? Not much room for margin of error in the above pic. Especially since you cannot see where the screw is going and what angle it is traveling at. I bet there are A LOT of split boards sitting on top of ICF walls because of that. Getting that exact angle right each and every time would prove challenging even for the most experienced builder, especially because you can't see what is happening underneath. If you hit it wrong and the SIP screw goes into the sliced portion where it is only 2" thick (most likely 1 5/8" at this point), the board sitting on top of the ICF wall will split, thereby making that screw hold down useless.

I will study this more but the above picture does not sit well with me. No disrespect to anyone, it just does not look engineered properly. It might be passable on paper but in the real world, I guarantee you that the SIP roof screw does not get embedded properly into that 2x8 each and every time. Most likely they will never notice this defect unless you get some really high winds and then your roof decides to take flight.




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10 Dec 2011 03:24 PM
I try to avoid using wood when concrete and steel are available.  Then again I live in the Southeast where termites are prevalent.
Residential Designer & Construction Technology Consultant -- E-mail: Alton at Auburn dot Edu, 334 826-3979
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10 Dec 2011 04:17 PM
How about cut the ICFs at the roof pitch, an pour likewise, and embed a strap like the Simpson MAB. Drill a hole through the SIP for the strap.
Brad Kvanbek - ICFconstruction.net
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10 Dec 2011 04:41 PM
Thanks Simon!

Lbear, I think it just doesn't look right to you because it is like nothing you have ever seen before. But I can guarantee you from first hand experience in using SIP screws (albeit not in this specific indication) that it isn't that difficult. Measure twice, cut once.... er I guess measure twice, drive once, in this example. Anyway, one can feel it if it is not penetrating properly and if it doesn't bite then the screw will not draw.

I agree with Alton, I would prefer a steel plate of some sort as opposed to wood. I don't see why that couldn't be worked out. But if you were nervous about a 4 x 8 being too thin you could use a deeper profile of lumber. Figuring out the angle at which to cut it is simple carpentry.

As for water intrusion, neo-washers are used and if installed properly will keep water out. But normally the SIP skin is covered anyway by a membrane or felt paper, and then a finished roof (asphalt shingle, metal, clay tile, et cetera).
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