Stucco Staining

Stucco Home.

10 Years Old.

No Plumbing in the wall in this area. One piece tub / shower installed at the interior adjacent to this stain.

Is it possible that the lack of Insulation within the wall behind the enclosure could be causing this stain from condensation?

Hi Joe,

The picture looks like most homes here…repaired and painted with an off color. But with a bath fixture next to the staining I can see why it might make you wonder, especially if its the only area with an off color.

Did you put a ladder up against the wall and see if its just the paint?

How long after it rained was the picture taken. Thinning paint job could be part of the problem.

How was the gutter right above the stain? Any holes or maybe being over run?

What direction does that wall face?

Wall is Northern Exposure.

Wall was not previously painted. It is hard coat stucco.

Gutters are clear, free draining and secure to the fascia.

Roof is in good condition. No staining apparant in the Attic.

Last rain was a week ago.

Stain is only in this one framed wall bay. It stops at the band joist of the 2nd floor and picks up again in the first floor wall (Dining Room).

Nothing indicating a problem at the home interior.

It is odd.

One would think that the vapor barrier (most likely installed on that apparent vintage home) would prevent that kind of moisture transfer.

Did you take moidture readings?

No Moisture indicated by contact meter.

Only a stain.

How did you report it, then?

Please let us know when/if you find out what it is from.

Hi Joe,

If is hard to believe thaat the staining is not the result of current or prior leakes around the tub. I would not think that it would be an insullation/condensation problem, The fact that it made it past the rim joist tells me that that is not the case.




That is what I found to be so odd as well.

The Faucet and plumbing is located on the interior wall opposite this area.

Tub is a one piece fiberglass unit. No seams at the tub ledge or corners.

No indication of staining on the walls and ceiling below. No indication of a prior patched repair either.

Hi to all,

Beats me as well then Joe especially as the pipework is not in that wall, I was rethinking the condensation issue especially if the hot pipe was in the wall but as that is not the case I don’t see where the condensation could be being generated.

I am just wondering if the finish coat is either thin or a little porous in that location.



Almost has to be a past or present leak looking at the picture again Joe.

Just the shape of it makes it look like water absorption occurred at some point in time…and Gerry stating the presence of the rim joist which looks pretty clear defined would make you think if water had run down the inside the joist probably would prevent that section from staining…very odd to say the least.

You better do some core drilling…:smiley:

May sound stupid, but where is the duct for the bathroom fan, Joe?

Usually that kind of a “stain” is due to a slight difference in stucco mixture/texture in that location.

At the time of construction, someone came in and either purposefully (plumber) or accidentally (roofer) damaged the stucco there and the stucco guys were able to “repair” it quite quickly (all things considered) so that there is little if any visual or noticeable difference between the repaired area and the area that was not repaired.

However, the repaired area was from a different batch of stucco mix, and since no two batches of stucco are exactly the same–ever–the batch used for the repair has slightly different wetting/drying characteristics.

This is why we endeavor to make enough stucco to completely stucco the home at one time. If we fail in our measurements there, then we at least use the different batch on a different wall. Never put two separate batches on the same wall because they will cure at different rates, possibly creating a crack in brand new stucco between the two batches, and will contract/expand at diffferent rates, also creating a crack between the two batches. It took me forever to explain the concept to the SOTB laborers until I demonstrated it on a 9-square-foot section using four different stucco batches. However, sometimes a picture truly is worth a thousand words, especially when one doesn’t understand those words because they are in a foreign language.

Ultimately, if the two batches of stucco mixture are too different, resulting in their wetting/drying/expanding/contracting characteristics being vastly different (all things considered), then the batch/area that stays wettest the longest will blister and slough first. This is why you occasionally see a blister fifteen feet from the ground, waaaaaay too far up to have been caused by absorbing ground moisture. I’ve usually found that the “stain” in your photo occurs near second-floor plumbing, especially if there was a spa tub installed in that location, and near second-floor windows. That’s because the plumber had to do some repair work, or install special plumbing for the spa tub, or a window was damaged by the roofers and had to be replaced, all resulting in damage to the stucco and repair with a different batch a few days or weeks later.

KB Homes here now understands proper stucco installation, courtesy of yours truly about four years ago, which could be the reason that KB Homes here regularly ranks at or near the top in homeowner satisfaction. And the #1 complaint? Stucco cracks. Indeed, they are ugly, but they also are not necessary if one understands stucco. Kind of like pool cracks, except not quite as serious as pool cracks.

With regular homeowner monitoring and maintenance (which should be done with stucco anyway), it should not prove to be a problem. But, again, regular homeowner monitoring and maintenance is key. Advise your client that stucco will crack and that he should walk around the home (or have a stucco professional walk around) at least once a year, note all the cracks, and patch/repair or otherwise seal and weatherproof them.

Just like inside, those exterior cracks usually will occurr diagonally at door and window corners (KB Homes here has learned how to prevent those common cracks, as well) and in large expanses of wall space, like on a two story building. Even if those cracks become long and wide, like from a first-floor window to a second-floor window, it typically will not be a cause for structural concern. It’s just a massive expanse of stucco that cured at different rates, just like a large expanse of concrete (KB Homes has learned how to prevent common concrete curing cracks, as well–Hmmm. I hope they paid me well. Hey, they did. Yahoo!!!). But as I educate my Clients in my reports, a common concrete/stucco crack can become a major concrete/stucco crack if it is ignored. In the case of stucco, ignoring those cracks can allow moisture to penetrate into the wall framing, and we all know what could happen once moisture gets into the walls. Uh-oh.

And why did I take such an interest in KB Homes, while ignoring all the rest? Because I had a KB Home.

No Duct and no Fan.

Bathroom has a window. Very few Builders will add the fan when a window is present.

Any chance that soap/shampoo/conditioner dispencer has a hole behind it?

It looks like the right height and location where the staining starts.

…just a thought.

If that much moisture has worked its way thru the sheathing to stain the stucco from the inside out. There are some major issues.

At least here they do install fans and ducts even with windows; but that’s not to say it is always or often done right. I inspected a condo conversion downtown Columbus last weekend and they had vented the bathrooms to the soffit area; not even to a vent. See picture.


Do a google search and put in stucco troubleshooting guide, there is a good PDf file that you can download with good descriptions about causes and preventions of stucco flaws.

And the Link is…???