Hi All

 

Has anyone manufactured panels using 9mm OSB for their skins. The reason I ask is that 12mm  OSB is hard to obtain in my part of the world and costly to import.

 

I would like to know what sort of problems may I be in for , and how does this  structurally compare with a 12mm panel ?

 

 

Many Thanks

 

Tonya

 

Hello Tonya,

Be careful! The strength of SIPs are directly related to the strength of the materials they are made from. OSB that is APA rated structural I has a strength measurement (modulus of rupture) of about 19.5 MPa (mega pascals), or about 2,800 psi (lbs. per sq. inch). The area (sq. inch) is measured as the cross section area of the OSB sheet, so if a sheet of OSB is say, 8' wide and 7/16" (11.1 mm) thick the area would be 42 sq. inch and the estimated point of failure would be about 117,600 lb force, or as commonly reported in the industry 14,700 lbf per linear foot. If the SIP is to be made from OSB of the same specification but is only 5/16" (7.9 mm) thickness then the cross sectional area for the same 8' wide sheet of OSB is now only 30 sq. inch. resulting in an estimated point of failure of 10,500 lbf per linear ft. (more than a 28% decrease). Most manufactures use a load limit (factor of safety) of about 1/3 of the point of failure (4,900 and 3,500 lbf per linear ft. respectively). (In reality there is a lot more to this factor of safety thing, but it gets a bit technical).

A note of prudence would be appropriate here. Estimated point of failure values are no substitute for testing and verification. In short quality demands basic and continuous testing.

Most manufactures base there span tables on data measured or derived from the type of information we have just discussed; hence my warning, be careful, if you do not change your span tables to reflect the change in the materials you construct your SIPs from, you could be headed to-ward's a rocky shore!

Good luck,

Matt B. Phelps, P.E.
SIP Engineering and Testing, LLC
mphelps@apec-llc.com

Depending upon what part of the world you are from, cement skins may be a better choice for you and your customers.

North America seems more accepting of temporay building components that burn, off-gas, mold, mildew, swell, etc.

Last I checked, modern OSB does not off-gas anything harmful.  Please correct me if I'm wrong.  Can't argue with the rest, but with proper design and construction you can keep OSB dry, which eliminates mold, mildew, and swelling.  Then you're left with burning, of course.

OSB has been know to off gas fomaldehyde , it would be best to see the manufacturers Material Safety Data Sheets to be sure what they are using

http://www.epa.gov/iaq/formalde.html

rmortman,
I would say you are mistaken. Remember the FEMA trailers??
One of the problems is that sometimes you have to look at who is doing the testing and who is paying for the results.
After the wax melts they put on it to give it the small amount of moisture resistance it has (to get it through the building process exposures) there is off gassing. People and pets do experience health issues as a result.
Of course it is covered by sheetrock--everyone knows that solves everything. LOL

I didn't follow the FEMA problem closely, but I had assumed it was particle board and MDF used for interior furnishings that was the problem.  I thought exterior grade structural OSB uses a phenol resin that contains formaldehyde but did not off-gas appreciably.  Perhaps they weren't using exterior grade OSB?

Anyway, I'm not arguing for OSB.  I think it's a questionable material to be using.  But it's cheap, and sometimes that's important.  Myself, I'd be looking at fiber cement or MgO skins.  Or, OK, metal, but only to make Chris Kavala happy.  (I haven't seen much on pricing of cement and MgO skins... I'm sure they're more expensive, but by how much?)