Please Help! Exterior wall problem. Can someone tell me what causes this?

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  #1  
Old 08-15-14, 11:49 AM
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Exclamation Please Help! Exterior wall problem. Can someone tell me what causes this?

I bought my house 8 yrs ago and now i'm seeing more and more of this around my house. I'm not sure if this is caused by water damage due to a hurricane or if this is caused by some kind of insect. I did have the house inspected for subterranean termites and they said that there's no sign of them. I was told that it might be caused by some kind of worm but i've never seen one. If someone can look at the photos and give me some advice as to what causes this and how to fix it before it gets worse i would be greatly thankful.
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Old 08-16-14, 05:02 AM
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this is severe,,, from what we see on this laptop screen, it appears your very fine home's been invaded by the deadly & prolific stucco weevil worm

not to worry - get rid of the moisture behind the wall & there'll then be nothing to loosen ( paint / parge / ? ) adhesion of the material that's falling off

good luck !
 
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Old 08-18-14, 11:49 AM
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I see this a lot in California. It is caused by moisture but the source is a little unclear in your case. Is this all close to the ground?

Scrape off what is loose
Wash the exposed stucco base coat with a weak solution of muriatic acid
Rinse thoroughly rinse again let it dry
Apply a liquid bonding agent to the exposed basecoat
Use Exterior Stucco Finish to patch it and match the texture.
As much as I am philosophically opposed to painting stucco, paint to match.

Actually paint is part of the cause of your problem but you are stuck with painting now so just do it.
In the future keep the wall dry.
 
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Old 08-18-14, 01:15 PM
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TC, what is it that makes you opposed to painting stucco It's always been my understanding that painting stucco helps it to last longer because it protects it from moisture.
 
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Old 08-18-14, 03:17 PM
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My experience is quite the opposite. All over the world Portland cement plaster and concrete are exposed to the elements without the "protection" of paint.
What I see is that when stucco is painted any moisture that gets behind the paint (and it does!) lets the stucco stay wet. When it is wet some of the soluble material in the stucco leaches out. The salts that are deposited on the surface of the stucco under the paint (efflorescence) are themselves hydrophilic, that is attract moisture and set up a cycle of more damage as the efflorescence blisters the paint and the problem expands and the damage deepens.
Also, it seems to me that paint on stucco lasts pretty well the first time but something about either the alkaline nature of the stucco or the lack of grip of the paint on subsequent coats does not last as long, peels and the cycle continues.
Paints are better now than they have ever been. Maybe paint will last longer now than it used to
I have seen unpainted stucco now almost 100 years old that looks good and painted stucco only 30 years old that has peeling paint and efflorescence, usually around the base.
 
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Old 08-19-14, 04:53 AM
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As ground moisture permeates the masonry construction it wants to evaporate to drier air. In the case of a parged wall with paint, as you have, the moisture is evaporating out in the area closest to the soil grade where it first " senses" drier air and will push the surface coating off the wall and continue to slowly break down the masonry at the area near ground level.

You may have also had a somewhat inferior stucco job done in the sense that fractures such as you have might be associated with shrinkage cracks in the original job due to a hastened drying of the stucco coats.

Is this an area that ponds water or is on the "receiving" side of the worst weather? Are your gutters overflowing at this area or is the condition consistent around the entire house?

If the possibility of removing all the paint exists you may want to investigate potassium silicate paints which typically have better vapor transmission characteristics and don't trap moisture as "tightcoat" has stated.
 
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Old 08-19-14, 05:08 AM
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The majority of my stucco painting experience stems from fla which sees a lot of rain. I do agree that poorly painted or use of cheap coatings on stucco doesn't fare well. Every masonry repaint failure I've seen has always been caused by poor prep and/or the application of the wrong coatings. Here in tenn, most of the stucco failures I see are caused by moisture getting in cracks and freezing during the winter. I understand there can big a big difference between climates and how that affects paint/construction.
 
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Old 08-19-14, 09:34 AM
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Time was we stuccoed right down to or even below the grade. Now days weep screeds let us terminate the stucco above the grade. I see less of this kind of problem where weep screeds are installed properly.
Calvert' explanation of the cause and effect is a good one.
Also I think that with the advent of pumps for stucco application that the stucco near r bottom of the wall is not worked and compressed as well as it was in the olden days. Plasterers don't like to squat or stoop so a pass or two with the Darby is all the base gets. So the stucco is not as dense at the bottom in modern stucco as it was when we put it on by hand. I think this because the stucco on houses where it was put on by hand seems to hold up better than newer stucco applied with a gun.
I am not faulting modern materials or modern ways. Simply stating one man's observations over 40 years.
 
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Old 08-19-14, 12:19 PM
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I wasn't questioning your facts so much as trying to understand them. I've only made stucco repairs occasionally although I have painted miles of it, more than half was 1 coat of stucco applied directly to cinder or concrete block. I always liked to drag my putty knife along the bottom so I could paint down to the bottom [sometimes below] of the stucco. Most [if not all] of the stucco I've painted has been hand troweled on. I don't recall painting stucco anywhere other than in the S.E.
 
 

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