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Yellow stain on exterior stucco wall after rain

Yellow stain on exterior stucco wall after rain

Old 01-02-03, 04:51 PM
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Question Yellow stain on exterior stucco wall after rain

I just moved into a newly constructed house with exterior stucco.
After rain, I noticed that there are yellow stain left on the exterior stucco wall (after the wall dried). It seems to seep out of the stucco wall at various places. Some are close to the edge of windows or lintel, some are just on plain wall.

Anyone can tell me if this is a problem? I am still in the warranty period. I want to know more about it before I talk to the builder. Any reference will be greatly appreciated.

Old 01-03-03, 07:27 PM
Join Date: Aug 2000
Location: USA
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Stains on stucco

From your description, the stains appear to be migrating from beneath or from an adjacent material. This may be due to paint pigmentation from windows, improper sealing or lack of flashing around windows, rust migration from lintels, moisture penetration behind the stucco, failure to use noncorrosive material beneath stucco, or some other reason. You need to talk with both the builder and the stucco contractor. You might also want to consult with an independent stucco contractor for another professional opinion. Whatever action you take should be done quickly and before the warranty runs out.

If you have synthetic stucco, one of the most common complaints has been moisture trapped beneath the stucco. Improper flashing, caulking, installation of foam board beneath. Water enters at joints between sections of the material and dissimilar materials, improperly sealed bottom edges, window and door flashings, poor caulking and gaps around decorative trim.

Because there are many sources of moisture penetration behind stucco, it is important to have the situation investigated immediately and appropriate action taken before moisture penetrates to the interior of your home. If stains are a result of acid rain, mud splashing, etc. on the surface, rather than moisture penetration from beneath, cleaning and keeping stucco sealed will minimize future staining.

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