Stucco discoloration II

Any idea what may be causing these stains ? Moisture? Ineffective kickout flashing? The wall pictured is the only one showing those stains. Any recommendations? Any help would be appreciate it.
This is a commercial building I’m just inspecting for practice.

Moisture staining. Looks like the sidewalks are discolored where the gutters are overflowing, so I’m going to guess that’s your culprit. Lack of kick out flashing is a major problem too, but that’s not what caused this. Hopefully someone who works with more stucco than we have around here will chime in.


I agree with Fred on the staining.


Yep, @fherndon1 has it right.

Poor drainage away from the building and gutter overspill keeps this area wet. Mildew stains and some moisture wicking also observed. Lack of stucco clearance compounds the problem,


Rain hitting that hard surface causing splashing. That is the reason log homes have large overhangs and the logs should be two foot above the ground. I call it the splash zone, which is bad for composite siding as well.


Several possibility’s could contribute to this, such as no drainage path, no kickout flashing BUT more probable …

There was at least one or more locations where concrete slabs, masonry or other flatwork were too close and touching the stucco wall(s). This is a common but improper building practice. There should have been about a 2’ space or gap where they meet to allow any future movement of the flatwork from causing cracks or moisture damage to the stucco walls. Stucco is porous and on drainage systems this can allow moisture to escape from behind the stucco.

Solution if Needed: Stucco industry details have flashing at the base of the wall or, alternatively, a 2” clearance above the hard surface with an integrated weep screed. Install proper flashing and/or weep screed per stucco manufacturer’s recommended repair details and specifications.


Wow thank you guys, great replies and thank you all for the information. Very helpful.

1 Like

Good point on the clearance issue by @bcawhern1 and @dbowers . As built I can’t see if there is a weep screed at the base of the stucco or not. Also, you might want to talk to them about the gutter design. It looks like the gutter on the left drains onto the lower roof right above the spot Brian circled, and the nearest downspouts are probably 20’ away. If they don’t want to relocate the downspout something as simple as a rain diverter at the overflow spot might help.


Yacdiel, are you in Florida where hardcoat stucco applied directly to block walls is commonly run down into the dirt without a weep screed? If so, you might find some valuable insights into Florida-style stucco in the following verbal “screed” written by an old-time Florida stucco man who’s now an engineering consultant and code inspector.

I’d be wary about calling those brushstroke-like stains mildew or otherwise caused by moisture because (1) in the photo there are also diffuse, blackish stains that are no doubt mildew mixed in with those vertical swaths, and (2) the brushlike vertical stains for the most part do not reach down to the paving, suggesting they may have been made by mechanical rubbing and not caused by water wicking/rising damp.

Whatever the answer is, your calling out the blackish stains has you covered by pointing out there’s a moisture problem in that corner, and of course, you called out the missing kickout.

1 Like

Good points, there is another possibility. Those brush like rust stains could be the lathe rusting and leaching to the surface. So many possibilities, so little time :smile:

Right, could be rust from the lathe if it’s stucco-on-frame. That’s a big one in coastal Florida where drainage planes can cause salty water vapor to rust out the lathe!


@dsmith32 I notices these throughout. Could they be from rusting lath? I am in Florida and it was stucco over CMU

images (13)
Maybe this?


No doubt the gutters and no kickout can add to things, but I’d guess the sprinkler head is the main culprit behind it.


Good eye sir!

1 Like

Well, something is oxidizing there. Maybe a fastener head that attaches the lathe.

Minerals in the water?

Not my first thought but possible, I was leaning towards the sprinkler just keeping the materials damp all the time.

There is no lathe. It must be stucco applied directly to the CMUs?

I am not sure how you would know if it does or does not have a lathe. This detail made me think it is possible.

1 Like