Why does stucco leak water into buildings?

We get many calls about stucco and water intrusion. I have one friend (he develops buildings) who hates stucco.
 Stucco has been around for a long time. Think of the beautiful stucco structures that are over 100 years old. The stucco was used initially on full masonry walls. It helps shed water and in some cases provided a sacrificial protective service.
 Really good stuff.
Office building with stucco and brick cladding

Office building with stucco and brick cladding

 So why is it a problem now
 Well, today it’s used it on materials different from masonry. We put it on steel or wood framing.  That’s different but not necessarily the kiss of death.
 Sometimes what looks like stucco is synthetic stucco or nontraditional stucco (I think of stucco being a three coat system).  That’s different as well but not necessarily the kiss of death.
 Sometimes stucco is considered the sole protective weather barrier—not as an integral part of the cladding system, but as the only protective system. And this is almost always the kiss of death.
What should I do if my stucco leaks
 First, find out where the water is entering the structure. Is it entering through the field of the stucco, at roof to wall connections (think of balconies as a mini-roof), or at openings (windows, doors, cable entrances, etc.)?
 If water is entering through the field of the stucco, you have a real problem. You’ll probably have to replace all of the stucco.
If water is entering roof to wall connections or openings, you can remove the stucco in those areas, properly flash and prepare the openings, and repair the stucco.
 If you find structural damage because of the water intrusion, you’ll have to replace the damaged materials.
 What to watch for
 Well, you bought a stucco cladding system to begin with—how do you know you’ll get a proper system the second go around? That is the $64,000 question.
 You may not have picked up on it, but I have used the word system throughout the discussion above. Stucco is an important part of the cladding system and it has to be tied in with the water barrier. If you screw up the water barrier, it doesn’t matter what you use for cladding. Note, there are other parts to the cladding system.
 Stucco is not bad for buildings
 I like stucco. It is pretty, durable, and nearly maintenance free. But the entire cladding system has to be designed and built properly.
 If you need help reviewing or designing a cladding system or if you have questions or comments, send me an email. Also, I’d appreciate any photographs you have of failing stucco or of successful stucco repair projects.