Stains on Stucco - dirt or water damage

[Tom Cissell]

I need help from inspectors experience with stucco. The stucco has stains on it on all side. Most look like dirt. When I tap on it the stucco seems solid. The worst area is under the double window in back. To a lesser extent the other windows such as in the second picture. How should I write this up? Thanks in advance.

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[Jerry Peck]

Almost looks like a flashing tape problem where the modified bitumen or other "sticky" backing is failing ("failing" for lack of a better term) where the sticky backing is being washed down.

I recall having seen some where the sticky backing was actually oozing out from underneath. I think someone posted some photos of that same thing (the sticky backing oozing out) here a number of years ago, but I don't remember who posted the photos.

[Steven Turetsky]

Hi Tom,

The photos show clear indications of water seepage. I recommend that the entire system be tested by a Moisture Analyst/Building Envelope Inspector to determine if there is damage to the substrate/structure beneath the surface, and why the system failed.

Simply rapping on the stucco to determine if there is damage will only hurt your knuckles. While the stucco may feel intact, the only way to test the system is to test for moisture content and resistance beneath the stucco. All window (bottom) corners, floor lines, kick outs, doors, etc, etc should be tested.

[Mark Reinmiller]

The staining is dirt or mold accumulation caused by water running down the trim above the stains. The staining by itself does not mean that there is a problem, but if there are problems they happen to show up most often at these locations (because of the extra water flow and because these are common areas where flashing or the WRB are not properly installed. If the house was built in the early 1980s or earlier there is a better chance that the stucco is ok then if newer. Anything in the past 25 year or so is suspect.

I have evaluated dozens of buildings where the wall sheathing (almost always OSB) is badly deteriorated or completely gone and the stucco seems fine.

[Tom Cissell]

Hi Tom,

The photos show clear indications of water seepage. I recommend that the entire system be tested by a Moisture Analyst/Building Envelope Inspector to determine if there is damage to the substrate/structure beneath the surface, and why the system failed.

Simply rapping on the stucco to determine if there is damage will only hurt your knuckles. While the stucco may feel intact, the only way to test the system is to test for moisture content and resistance beneath the stucco. All window (bottom) corners, floor lines, kick outs, doors, etc, etc should be tested.

Thanks. Will do.

[stanley frost]

I agree with Steven. Another problem may be where the second floor stucco terminates at the trim. If the contractor sealed the gap between the bottom of the stucco and the trim there is
no way for any moisture that penetrates the stucco to drain out.

[John Kogel]

I think that is moisture coming from the interior, condensing on the cool back of the window flange and bleeding down over the stucco. Throw on some soot and algae and you got a stain.

The framing and sheathing should certainly be checked, especially is the sheathing is OSB or some kind of fiberboard.

[Tom Cissell]

I think that is moisture coming from the interior, condensing on the cool back of the window flange and bleeding down over the stucco. Throw on some soot and algae and you got a stain.

The framing and sheathing should certainly be checked, especially is the sheathing is OSB or some kind of fiberboard.

Thanks guys. I have advised the client to have a moisture intrusion test and have shown them a video from CBS Philly about homes with similar stains that needed extensive repairs.

[Mark Reinmiller]

Thanks guys. I have advised the client to have a moisture intrusion test and have shown them a video from CBS Philly about homes with similar stains that needed extensive repairs.

I missed that report. I think Kevin Thompson was interviewed for that. We have worked together on several large projects with stucco problems. I see these problems all the time.