Swell of OSB with Repeated Wetting

[dcarr82775]

I am looking for information on Oriented Strand Board swell characteristics as well as nail performance due to wetting. I need to decided what to due with some houses where the OSB shearwalls have water damage.

Thanks

 

[KootK]

This won't answer your questions but may be useful for background information if you don't have it already: Link

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[jayrod12]

Remove it and replace it. Regardless of the fact that it generally requires removal of significant finishes.

Provided you fasten in the patch pieces around the perimeter sufficiently you aren't necessarily required to remove the entire damaged sheet but just the damaged portions.

I would not be trying to determine what extent of capacity is remaining. I've always just assumed once wetted to the point of swelling then the whole sheet is useless.

 

[Ron]

dcarr82775....in tests that I've run on OSB edge swelling, it can be as much as 20 percent. I have not run tests on overall volume change, just edge swelling. I have seen the gap close between boards that were supposed to have the typical 1/8" gap at all edges when constructed. This was from water intrusion behind stucco.

All fasteners are affected by moisture intrusion to OSB...nails, staples, screws. Depending on the level of moisture intrusion, I've seen head corrosion with some section loss, to full shank corrosion with complete section loss.

Our "rule of thumb" is that if the OSB is stained, it gets removed, since the volume changes are not generally recoverable.

 

[dcarr82775]

Thanks Ron. I have seen 20-25% for thickness swell in a document so that is in line with your tests. I am hesitant to simply say remove and replace since it is litigation. I try to leave things alone unless I really think there is a problem. The only areas I am concerned about structurally are the shearwalls. I have to think the nail capacity is significantly degraded, but no idea by how much

 

[Triangled]

ww.apawood.org has often been helpful to me.
APA-EWS
been awhile since I looked at it, but as I recall, reduction in shear value is significantly more for wet osb

 

[Ron]

dcarr82775.....at the very least, you have to consider in your analysis that the wood is now in "wet service" (moisture content above 16%). That alone will reduce the shear wall capacity.

Further, any loss of section on the fasteners greatly compromises the shear capacity of the shear wall since the fastener shear controls in this case.