Thread: Exposed OSB

Do you identify exposed OSB in this area, undera ledger of a covered deck. The house was built in 2003.

Thanks

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That might be an OSB rimboard product, although looking at the nailing pattern perhaps not.

OSB Rim Board – LP

I probably would. It's such an easy fix in most cases. Usually, there will just be some siding over it that is caulked/sealed to the bottom edge of the ledger. Of course this is on the presumption that the ledger itself is properly flashed, which it appears to be from below.

The appearance of nails and the blue 16"OC line looks like OSB, It appears to be properly flashed and no evidence of moisture in 6 years, is there a problem ?

In New England we can have a few days of rain where everything is just damp or wet, even if it is not out in the open. So around here I would at least recommended covering OSB just because of how it can weather poorly.
I make the same comment if it is under a bay window or other bump out. I don't get dramatic about it though. Just a good homeowner tip.

Looks to me like that might be the wall sheathing nailed to the sill plate with the ends of the floor joists on it, is there even backing for that ledger to be nailed to?

Or maybe this was along the side with the first joist serving as as the back-up? There is a hold-down strap, so it could be.

it is wrong in my world. no weather resistant membrane on an exterior wall as required by code.tar paper, tyvek or equal should have been installed behind the ledger board.

That's just OSB wall sheathing. Not OSB rim board. Rim board wouldn't have the nail lines painted on it. It should be covered.
R703.1 MRC Exterior walls shall provide the building with a weather -resistant exterior wall envelope.

I hope you don't mind the new guy jumping in but I agree with door guy, OSB is not designed as an exterior grade siding. The fact that it is under a deck may even be worse due to the reduced air circulation to help keep it dry. Covering it with house wrap or tar paper is not a permanent solution either. It should be covered with exterior grade siding material, preferably matching the rest of the wall above.
BTW, the ledger does not appear to be bolted to the house, only nailed. Jerry also brought up the question of what the ledger is actually attached to. Is there blocking behind the OSB? if so what is the blocking attached to and by what means? Lastly the flashing visible from below appears to resemble aluminium. If it is, and the lumber is ACQ or CCA treated, that flashing may already be compromised.
One more thing and I will shut up. I thought the rule was we had to use our real names here. Whats up with door guy?

Originally Posted by Steven Stafford

One more thing and I will shut up. I thought the rule was we had to use our real names here. Whats up with door guy?

Steven,

It is a preferred rule, not cast in stone, and is done for common courtesy among ourselves.

There are some who have been asked to contact Brian and have Brian change their usernames to their real names, some have refused (not doing so is the same as refusing, for those who just got their feelings hurt ) - those include (just a sampling of some): doorguy, deckexpert, inspector3500, etc., not that I am poking them in the eye with this or anything (which I actually am doing because they deserve it).

Another new guy jumping in - for what it's worth - this is how I typically address exposed OSB under a fireplace bump out:

Observation and recommendation:

The underside of the fireplace bump out is sheathed with Oriented Strand Board (OSB). This type of sheathing is generally not rated for exterior exposure. (OSB without an exterior APA rating should not be left exposed continuously to the elements for more than 90 days)

As is, this material is susceptible to moisture-absorption from the atmosphere and possibly from contact with accumulated snow. This moisture exposure could result in premature structural failure of this sheathing.

This exposed sheathing should be sealed against moisture exposure. Methods to accomplish this are scalable and include, but are not limited to:

- Sealing the surface with several coats of polyurethane and sealing all exposed edges with a high quality exterior caulk.

- Installing house wrap (Tyvek or a similar moisture management material) over the exposed sheathing, and vinyl, metal, or pressure treated plywood cladding over the house wrap.

The detail of how to finish the base of a fireplace bump out is the choice of the builder. The local authority having jurisdiction (building code enforcers) likely approved this as acceptable and therefore the current owner is not obligated to modify this, nor will they likely be willing to. Home inspectors are advisors - not enforcers.

As an inspector of existing dwellings, I have had the opportunity to observe failed OSB sheathing in this location. Failed sheathing can fall free from the home and make the home susceptible to moisture and pest intrusion and damage.

I recommend that you consider protecting this exposed sheathing from the elements.

Couple of things here, since we are all fixated on the OSB, it appears that the floor joists are not treated, The rim/ledger seems to be just nailed to the sheathing wall studs.We are talking about the roughly 6" of exposed osb that's been there 6 years and looks virtually new. Maybe that deck not only has a roof but is enclosed as well. I'm not sure I see any evidence of water runing down on the floor joists between the deck boards. Depending on the enclosure around the deck both below and above the floor joists this maybe more of a crawl space and not fall into the strict guidelines of exterior space. Based on the rust on the nail heads, covering the OSB would be prudent but insureing that the other items are noted is important as well.