Wet OSB under siding -- maybe

Hi! A friend is helping us with electrical work, and recently did the rough-in for a bunch of external light fixtures and outlets. That meant that he cut through our new siding, and the Tyvek and OSB walls underneath. Before we had the rough-in inspection, it rained a few times, and water came into the house through the openings around the electrical boxes. I am not concerned about water that came into the house, because I can see whether it dried. But I wonder whether water got between the Tyvek and the outside of the OSB and whether I should be concerned about mold development. Should I be? How do we dry that out? He wants to install the external fixtures now, but I wonder if that means that we would be cutting off the needed airflow to any wet areas. Thoughts???????
Thank you!

 

The tyvek is vapor permeable so it allows the osb to dry to the outside. Your only VB should be directly under your drywall, thus everything to the outside will dry to the outside.

The additional concern is proper flashing around the new installs. Siding needs to be pulled back and flashing overlapped such that any water entering is directed back to the outside.

My only other concern would be just how wet did the wall cavity get? If it is soaked in there, even though the tyvek will allow moisture to move to the outside, it is a slow process. Sealing up a LOT of water would not be good. If your siding is vinyl, it comes off very easily allowing more osb to be opened up, everything dried, new insulation if needed, and closed back up, 2 hr job, and when done, a lifetime of satisfaction it was fixed right.

PS, welcome to the forum

Bud

 

Damp siding should be able to dry out from the inside in new construction.

 

Thanks, Bud!
I wish I knew how wet it got...but I can't tell, because any water that entered did so by going through the openings around the new electrical boxes. The siding is HardiPlank, so it's not easily removed, unfortunately.
From what I can tell, it did not get so wet that the water soaked through the OSB to the inside wall, but it could be wet on the external side. Our friend has now covered up the openings with duct tape until he installs the fixtures...so now no air is coming through that way.
I hope you and airman.1994 are right and that there is enough circulation to let the OSB dry out.
I'll talk to our friend about the flashing.
Thanks!

 

With a one time event, you should be fine; mold develops most often with repeated moisture infiltrations. To that end, make sure everything is sealed/flashed correctly so you don't get any more water in that space.