Owner Beware: Stucco is Not Maintenance-free

In our last Advisor issue, we discussed stucco on residential homes and common issues found in those built over the last two decades. If you are the owner of one of these types of homes you should be aware of typical signs that there may be water infiltration and take the steps discussed below to prevent potential problems in the future.

As detailed in our previous article, water can get into the exterior building envelope, including the stucco wall system through cracks, improper sealants, improper flashing, and high-sitting plant beds. Keeping up with the maintenance of your home in these areas is the easiest way to prevent moisture issues. Performing a simple visual inspection of the exterior of the wall system on a regular basis (once or twice per year) for holes, significant cracks, or separations as well as noting changes from your previous observations is a great way to keep yourself abreast of potential issues.

You should also take some time during or immediately following a heavy rainstorm or the melting of a large snowfall to observe the reaction of your walls.  If there is water getting into your house or your stucco system, this is when it will be obvious.  On the inside, pay close attention to the areas where the walls meet the ceilings as well as around windows.  At the exterior of the home, telltale signs of moisture are sustained darkened spots on the stucco, usually found under windows.  If the water marks don’t lighten up after a few days, the wall system in that area is having a hard time drying out.

Preventing Water Infiltration and Retention

Surface cracks should be noted during your routine inspections and compared to previous observations. If they are noticeably bigger than previously seen, moisture testing in that area should be conducted. In the meantime, a breathable clear coat should be applied to the surface of the stucco to prevent moisture infiltration into the microscopic cracks.  If cracks that are found exceed around an eighth of an inch, you should have a contractor perform a proper restoration.  This restoration typically involves either the crack being cut out and patched or the installation of a control joint.

Improper or cracked sealant around windows, doors, roof eaves, and other wall penetrations is one of the biggest culprits in allowing water to infiltrate the stucco system.  The life span of sealant (or caulk) varies depending on the type of material and weather conditions, but it typically should be replaced every three to five years.  Common sealants used on stucco systems include silicone, polyurethane, or acrylic.  When replacing the sealant, the old material should be cut out prior to the installation of new sealant, which should be applied to a clean surface.

If there are no visible cracks or problems with the sealants but water is still appearing in areas it shouldn’t, the flashing of your windows, roof, or doors may be an issue.  The first thing to do is make sure the weep holes in the window or door frames are clear.  The weep holes are an integral part of the flashing system as they allow rain water and melted snow or ice to drain from the outer part of the window sill.  Weep holes are small narrow vents or holes that are usually found pierced through the outer vertical rib that projects upward from the base of the window frame.  In order for weep holes to function properly, they must be free of sealant, stucco, or other debris.  If the weep holes are clear and you suspect the water problem is still due to the flashing, then you should contact a contractor who can compare the window and door manufacturer’s instructions to the construction of your system.

The easiest part of the regular inspections a homeowner can make is looking at the mulching beds around your property.  Many wood framed stucco homes are built with a weep screed at the base of the stucco at the foundation plate line.  The weep screed is a continuous metal mesh that allows for rain water or melting snow that may have infiltrated the wall system to exit.  It is imperative that the landscaping around the base of the stucco wall be below the weep screed to allow for this downward flow of water.  If you find your plant beds are too high and you cannot see the foundation wall below the stucco, then you should dig them out until they are at an acceptable level.  If you do end up needing to do this, always make sure the ground still slopes away from the exterior walls so that water drains away as needed.

The purpose of both weep holes and weep screed, as indicated by their name, is to enable water to “weep” from the wall system.  In other words, both assume that the wall system will have water entering at one point or another.  Moisture within the wall for a short amount of time will not do damage.  The harm is done when the wall is damp for a sustained period. Since the walls “dry out” from all directions, having a high interior humidity can impede the drying out process.  Contributors to the accumulation of water vapor in the house are showers, washers, dryers, and furnaces.  Proper air circulation of these areas is a simple solution to this issue.  This can be achieved by opening doors, increasing ventilation, using exhaust fans in kitchens and bathrooms, cleaning the dryer vent regularly, and running a dehumidifier on damp days.

Repairing Moisture Damages

If you find sustained moisture in your stucco wall system despite taking the above steps to mitigate damages, the final recourse is to repair the wall.  The first step for repairs is to hire a reliable moisture testing expert to perform moisture probes in the suspected damaged areas.  Their findings will come in the form of a report indicating the moisture level at each tested spot as well as the weather conditions on the day of the testing.  Moisture levels in the wall system may vary depending on the season, face of the wall, and recent storm conditions.  A moisture level over approximately 20% for a sustained period of time will begin to cause deterioration of the wood substrate behind the stucco.

In areas where a reading of 20% or higher is taken on more than one occasion, repairs may be necessary.  An expert should be brought in to determine exactly what is causing the water infiltration and how to prevent it from occurring again prior to any major demolition work.  After the root cause is determined, the repairs to the walls can begin if deemed essential.  In some cases, there are enough locations where repairs are needed where it is easier to remove and replace the stucco and wood substrate on the entire face of the building envelope.  Oftentimes, however, patch repairs to the stucco may be made in select places of damage.

If the stucco is restored in the mended area and the color cannot be matched to the original adjacent parts of the wall, the face of the house can be painted in order to blend the patch for better aesthetics.  Paints that are 100% acrylic are permeable and will allow walls to continue to breathe and dry out.  Alternatively, a colored stucco finish coat could be applied to the wall for color consistency.

Patching and either refinishing or repainting are both much more cost-effective options of repair than the complete removal of an entire wall of stucco.  Removal of a wall or portion of wall that has no indication of a problem is imprudent and may actually pave the way for more problems.  As the old adage goes, “if it ain’t broke, don’t fix it.”

Despite the reputation that stucco homes have gotten lately, it is possible to own one for years and not have any major problems.  Just like with any type of home, routine walks around your home, regular maintenance, and the occasional visit from a stucco expert (not unlike having a plumber or electrician if needed) can prevent a lot of worries.  MDC Systems provides consulting services for building envelope assessments based on years of experience with stucco wall systems and the use of WUFI software for moisture analyses.