We are having a new SIPs home erected right now and I am concerned about panel bowing and sound transmission. Our location is Minneapolis, MN in the city. The walls are 6" OSB-EPS. Conventional joists for the roof. Marvin Integrity windows. I understand that sheet rock clips should be used at the intersection of interior walls and SIPs. What about SIPs-SIPs corners and SIPS-ceilings? Anything special to be done there? How do you keep SIPS walls from bowing way from kitchen countertops (16' of counter along outside wall)? I have heard that SIPs are quiet and read that they are noisy. This is a small house on a small lot with busy road 500 feet away. The windows are ordered so I don't think I can Hi Hat now, or can I? Thanks

Markoch,

I'm a little confused (but I'm getting used to it). Are your panels bowing, or did someone tell you they will? They are not supposed to bow (none of mine have) and if they are bowing, contact your supplier and tell him about it. As long as they are protected from long term exposure to moisture, SIP panels will retain thier strength and straitness. The panels get thier structural strength from being straight.

Normally, drywall clips are used where you have trouble placing a drywall nailer. If the interior wall stud is glued and screwed to the SIP wall, you have a stud attached to the panel which gives you a nailer, and I really don't see any need for a clip there, or for that matter, at any SIP to SIP junction.

I've had people comment that my house was the quietest house they've ever been in. I've heard other people say that SIP homes transmit alot of noise. If you are concerned about noise, my suggestion would be to fir out the front wall (for a dead air space) and use Quiet Rock drywall on the front wall and side walls. You can also purchase a foam tape that will stick to your firring strips to also reduce vibration and noise.

At least, IMO

Steve
GrandCountySIPs.com

Posted By markoch on 06 Mar 2011 12:05 PM
We are having a new SIPs home erected right now and I am concerned about panel bowing and sound transmission. Our location is Minneapolis, MN in the city. The walls are 6" OSB-EPS. Conventional joists for the roof. Marvin Integrity windows. I understand that sheet rock clips should be used at the intersection of interior walls and SIPs. What about SIPs-SIPs corners and SIPS-ceilings? Anything special to be done there? How do you keep SIPS walls from bowing way from kitchen countertops (16' of counter along outside wall)? I have heard that SIPs are quiet and read that they are noisy. This is a small house on a small lot with busy road 500 feet away. The windows are ordered so I don't think I can Hi Hat now, or can I? Thanks

I think the bowing is an isolated case and the poster is not disclosing the whole story, I have installed all types of SIPs and never saw that condition, I can only conlude that it is releated to improper installation

6" walls are noticably better than 4" for sound transmission, hi-hats are as shallow as 7/8" or you could use a 5/8" RC-1 channel, then extension jambs on the windows. But I don't think that you will have a problem with 6" walls
Good insulated glass windows have much to do with keeping sound out as well as window coverings

Thanks for the reassuring remarks.


I had heard about the bowing on the Building Science web site and it is also mentioned on page one of my blueprints from the SIP manufacturer. It is mainly an issue in northern climates. Maybe it is more pronounced with 4" panels and my 6" panels won't do it


Here is a typical quote from a 2010 article.

Another issue that has surfaced as a potential concern is panel bowing. This movement is a result of volume changes. As moisture levels rise or fall, the associated expansion of one skin or the other can cause the panel or wall assembly to bow.

The greater the span of the wall panel and the thinner the foam core, the greater the potential for bowing. The good news is that avoiding the conditions that lead to panel bowing is largely controllable. This would
include avoiding thin panels that span great distances (greater than 12 ft), sudden forced heating and dehumidification when the exterior of the wall assembly is at elevated moisture content, and back ventilating the cladding to ensure a controlled and lower level of moisture.

markoch;
"volume changes" sounds like a nice way of saying the OSB is swelling, get the building up quick and minimize exposure to water and you will be OK

Yes panels can bow.
I've dealt with this issue on a number of occasions and it was never an installation issue. It has been a function of pushing the limits of design as well as improper detailing of exterior cladding. The lack of proper control over bulk water and/or the lack of back-venting where needed can elevate the moisture content of the SIP skin. This change of moisture level (volume change) will cause expansion.
If the SIP expands on one side only, it will bow. Let it dry back out (or cool back down for the metal version) and it will straighten.
It's largely an aesthetic issue unless it creates cracking on finish materials. The use of thicker panels will help, the use of embedded lumber or similar at panel joints will help. The use of interior walls designed to act as shear walls will stiffen the exterior wall and greatly reduce the movement should your exterior detailing fall short.

All interior partitions should be attached to the exterior SIP by attaching with panel screws that penetrates the SIP and attache to the stud that adjoins the exterior wall.

Noise in SIPs can occur in two forms. Airborne noise or contact noise.
Panel thickness has little to do with performance. Properly installed SIPs that create an airtight structure will create a noticeably better performing shell as it relates to airborne noise. This is where you need to realize that windows, doors, and truss roofs may be your weak link when discussing (airborne)sound. Contact sound can only be reduced by adding mass and creating a disconnect between the SIP and either interior or exterior cladding (like firring the drywall or adding stone on the outside.
SIPs perform very well in the real world of sound until exposed to high energy low frequency sounds. (One area used to establish STC ratings) This high energy low frequency sound is seldom experienced outside most homes unless you live next to the tracks, under the flight path or your neighbors kid enjoys rap music from his 20gazillion watt stereo with the base turned all the way up.

Al

As someone in a Northern climate looking at SIP (PUR specifically), is the lack of framing in PUR SIPs cause for concern relative to bowing?

Brain