Cause of wood damage?

[palmettoinspect]

This is the OSB wall sheathing behind the vinyl siding chimney chase in contact with the perimeter concrete block wall. Is it just moisture “wickingâ€

[Bain]

It's difficult to know what's going on with just one photo. Do you have an exterior angle?

Lots of times, when the J-channel is installed directly on top of the deck flooring, water seeps beneath the J-channel and causes what your photo depicts.

[palmettoinspect]

Nope no other shots. However there is "J" channel trim installed on top of the deck as you described. Thanks

[Tom Raymond]

I've modified your pic. Is this what we're looking at?

Click to Enlarge

72.41 KB

If so, the OSB is being soaked by the run off from the deck flashing. It should have been covered.

Tom

[Erik]

Flashing should have been on top. To catch the water before it goes behind the ledger.

[hausdok]

Flashing should have been on top. To catch the water before it goes behind the ledger.

Well yeah, unless they're doing something like this:

Click to Enlarge

79.86 KB

or this:

Click to Enlarge

34.81 KB

ONE TEAM - ONE FIGHT!!!

Mike

[Erik]

Mike, I am not a fan of your first diagram I don't now how many times I have seen the space between the flashing and ledger full of Leafs. Allowing the moisture to accumulate and rot the ledger. Second one I what I like to see.

Nevertheless from what I can see in the picture. I don't like the fact that the OSB is setting or in contact with the concrete foundation. But it appears the water is coming from the behind the flashing. I would look to see if the flashing was installed properly. If it is start looking at roof, window, and door terminations.

I have seen OSB exposed under a deck that was flashed properly and it was fine by the time I got to inspect it twenty years after it was installed. I don't think the fact the OSB is exposed would be why it rotted. Something else is going on.