EIFS Failure due to poor installation practices (C) Daniel FriedmanWeather-Related Causes of Paint Failures on Stucco Exterior Walls

  • STUCCO WAll FAILURES DUE TO WEATHER - CONTENTS: Stucco wall paint failures caused by weather conditions. Too hot, too cold, too dry, too wet, too windy, too sunny: conditions affecting the success of a stucco exterior wall application. Stucco exterior cracks, white deposits, stains, efflorescence causes. The role of weather conditions in the success or failure of exterior stucco jobs
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Weather-caused stucco wall coating or paint failures:

This article reviews common weather-related causes of exterior stucco problems and failures when installing modern stucco or EIFS building exteriors.

We include photographs of weather-related stucco failures on buildings useful to assist in diagnosing the probable cause of stucco wall coating failures such as stains, efflorescence, blotching, cracks, and leaks.

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Water & Weather Impact on Inspection of Painted Stucco Surfaces

Stucco before wetting (C) Daniel Friedman

The diagnosis and cure of paint failure on buildings, particularly on wood siding and trim, is quite possible if there is a careful and thorough inspection of the building, its history, its surfaces, and the actual points of paint failure.

It is diagnostic to compare the same coating on the same type of surface at different locations on a building and in areas of failed and not-failed paint.

[Click to enlarge any image]

Water or wet stucco combined with high pH is the problem. It is the combination of painting over a still-wet stucco surface or still damp surface, or a surface that is subsequently exposed to abnormal wetting, along with high alkalinity that causes saponification of an acrylic paint on stucco.

When painting a sufficiently dry stucco surface, alkalinity alone will not cause this problem. - paraphrased from KTA Tator, a Pittsburgh consulting firm.

As our photo demonstrate, the appearance of any painted surface, particularly new stucco, can be significantly different when it is wet.

Stucco before wetting (C) Daniel Friedman

While there is nothing abnormal or "wrong" with a painted surface that looks a bit different when wet, say darker in color, streaks or the appearance of mottled efflorescence or white blooms on a wall after wetting may be telltales of a paint problem, and certainly these inconsistencies mean that a paint failure investigator needs to inspect when the surface is dry. Inspecting in the rain or just after raining or other sources of wet on a building exterior may lead to incorrect conclusions.

White Run-Down Stains on Exterior Stucco after New Paint Job

Below we show several photographs of ugly white stains that appeared quickly after a reader's home's stucco exterior was spray painted in 2010.

Stucco wall stains after painting (C) Daniel Friedman

The reader indicated that the painters applied a Dunn-Edwards exterior flat acrylic paint very quickly, perhaps too quickly, after the home had been power-washed. The stains are most likely not due to a defect in the paint itself (unless it was amended or over-thinned by the painter) and more likely due to improper surface preparation combined with painting before the surface was dry after power washing.

Stucco wall stains after painting (C) Daniel Friedman

The Importance of Weather to Stucco Work and Stucco Paint Coatings

As detailed at STUCCO WALL METHODS & INSTALLATION and also adapted from the printed text Best Practices Guide to Residential Construction:

EIFS Failure due to poor installation practices (C) Daniel Friedman

Moisture, humidity, rain, or wet conditions during thin-coat or EIFS stucco work can lead to a subsequent series of failures of the entire installation.

The home shown in our photo (left) was the subject of litigation. We observed that the final stucco had been applied over wet surfaces and in some cases over surfaces that also had been troubled by soil that had splashed-up on the building during rainy weather.

More about the lawsuit that ensued can be read at "EIFS Lawsuit Mistakes & Photos" found in SIDING EIFS WALL LEAK POINTS

Stucco wall paint failures are also traced to moisture, efflorescence, and failure to adequately clean the exterior and then allow it to dry before painting. See P AINT on STUCCO, FAILURES and also PAINTING in SUN or WIND.

Temperature during stucco work will speed up or slow down the hydration process that cures the cement in stucco. It is best to avoid application in extremely hot or cold temperatures. In hot, dry, and windy weather, frequent misting will be required on the scratch coat or the installer may need to tape polyethylene sheeting in place for proper curing.

Question: minimum temperature for applying stucco systems

2015/12/27 Anonymous said:

What is the lowest Fahrenheit temperature for applying stucco?


Anon: 40° F and for stone facing systems, 50° F and rising. The "and rising" means that the temperatures should be on the way up. Don't apply stucco at these temperatures at a time when temperatures are expected to fall. BASF warns that not only will stucco system materials using controlled set times set up more slowly at lower temperatures, in conditions of cool temperatures and high relative humidity they may not set up at all!

According to typical stucco system installation instructions such as BASF's Technical Bulletin "Cool Weather Application of EIFS, Stucco
and Acrylic Surfacing Systems", we quote this excerpt:

When air temperatures begin to fall in the autumn or when they begin to rise in the spring, special considerations must be given to application of EIFS, stucco and other acrylic surfacing systems. Application of cementitious and acrylic materials is typically restricted to temperatures of 40° F and rising. This minimum is critical to the proper curing and overall performance of the products. Acrylic coatings will not develop physical strengths properly or coalesce to form a film correctly in temperatures below their design standard. (Specialty or stone finishes that are contained within an acrylic matrix tend to be even more temperature sensitive and are restricted to application at temperatures of 50° F and rising.) Application of materials in cool, cold and freezing conditions commonly cause materials to crack, flake, soften or delaminate. - BASF, op.cit.

Stucco effloresence (C) Daniel Friedman

Direct sun tends to dry out the fresh stucco too fast, so installers should try to follow the shade around the building. Also, retardants are available that can be sprayed on the scratch or brown coat in hot weather to slow down the curing.

Sun, heat, and rapid drying conditions can present special stucco application troubles or subsequent stucco paint coating troubles in hot dry climates such as the American Southwest. (Photo at left).

Cold weather also presents problems. Stucco should not be applied under 40°F, and it should not be allowed to freeze within 24 hours of application. Accelerators can be added to the stucco mix in cold weather, but these can weaken the material, and calcium-based accelerators can lead to efflorescence.

Heating the materials and, if necessary, tenting the structure can permit work to proceed in cold, even freezing, weather.

Cool, moist weather is ideal for traditional stucco wall installations. In humid weather, with relative humidity over 70% or heavy fog, misting is not usually required.

Effloresence - white salts, deposits, and stains in stucco systems are often weather related.

It has been observed that efflorescence is usually a seasonal problem associated with cooler weather. Cooler days and nights seem to bring out salts that are not as evident during warmer periods. The cause behind cold weather efflorescence can be linked to seasonal variations in the evaporation of moisture. Under warmer or hot conditions the rate of evaporation may be very high so that the moisture evaporates within the cladding rather than on the surface. In colder weather, however evaporation may be very slow allowing moisture to move to the outer surface of the plaster/stucco before it evaporates leaving the salt deposits on the surface. Following the proper cold weather processes may reduce and/or eliminate some of the efflorescence experienced during the cooler months. - Griffin, Mike, Quikrete, op.cit. (see below). 

See details about the cause, diagnosis, cure, or prevention of paint failures on stucco exterior walls, found at STUCCO PAINT FAILURES.

References on Weather Concerns for Plaster & Stucco Application

Stucco Finish System Articles


Continue reading at STUCCO WALL METHODS & INSTALLATION or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see SIDING EIFS WALL LEAK POINTS for a photo guide to common leak points in synthetic stucco applications.

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