Moisture staining on the common wall. Any one see this before?

Moisture staining on the common wall between the house and garage. I noticed some of the stains were right in line with the wall studs.

I checked the roof in this area (where the garage roof meets the wall of the house) and it appeared to be fine. No visible flashing - vinyl sided.

I checked the stains with a moisture meter before going into the house and one of the stains in the drywall was at 20%. It started to rain while I was doing the inside portion of my inspection. When I was packing up to leave I checked the same stain that was 20% and found it to be 50%.

I recommended a licensed roofer evaluate and repair as needed. The buyer contacted me and said the roofer didn’t find any issues.

This has to be coming from the roof. Anyone have experience with the same type of issue - stains in the common wall nothing visible in the attic or on the ceiling?

I suggested removing the drywall in the garage to trace the stain to the leak. Any other advice is appreciated.

Have a blessed day!


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Was the staining only located on the bottom sheet or in other locations as well? Did you by chance check other areas to see the percent moisture to compare readings?
Was the garage a conditioned space?
Lots of questions but not many answers yet.

First question… is the garage a ‘conditioned space’?

Looks like condensation to me… or perhaps wet things hung there or leaned against the wall to dry…

certainly not a roof problem

I agree Bill, this is not a roof leak. :slight_smile:

In that part of the country I suspect the kids leaned their snow sleds or other wet toys against the wall.

No it was not a conditioned space.

Yes I always compare non stained areas with the stain. If I remember right before the rain my meter was showing 20% at one of the stains and 12% or so on a non stained area over a stud (just like the stained spot). About two hours later I checked the 20% stain and it showed 50%.

Yes there were stains on the panels above but not a lot of consistence (see over all pic below.

Thank you for your thoughts so far.

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I highly doubt the roof is leaking, might be water entering in back of siding, but like others said, looks like wet items placed against the wall.

Certainly just cannot place a moisture meter on a wall and make any determination with regard to its origination without destructive testing, or possibly a thermal imaging camera if there was a delta-T or you make one with heat. Regardless, even then holes would be needed in the wall if the stains enlarged to actually see what is going on.

Almost impossible to see from afar but those stains appear consistant with where a cripple stud would be between the studs and if so moisture traveling down the dry wall would not indicate moisture until it stopped at the cross stud which would make some sense to me. Other wise I like everyone else is just guessing

It does look like they placed wet items against the wall and maybe this is where some of the stains came from.

I was going to just note the stains in the report and not make an issue of it. It was raining so I decided to check a few of the spots before leaving and sure enough one of the spots was wetter.

I told the buyer it wouldn’t take much to remove three sheets of drywall and take a closer look. This would be cheaper than paying for an IR inspection.

I told him to give me a call if he can get permission for me to go back and take another look. It has been raining here for two days.

I will post more info if I have it. Just thought someone had a similar issue and could say yep been there done that…

Good night

I think this is a good guess. It has to be a leak if it got wetter after raining (soft rain) for two hours. Maybe my meter or my eyes are playing tricks on me.

See it almost everyday in unconditioned garages. Condensation. Rarely anything other. You are getting the differences from the surface moisture (humidity) due to the cold temperature. You see the staining primarily where something was touching those sections of wall. You see it again at the small white wire thingy above those stains.

Thank you all!