Is A Stucco Home A Cause For Concern?

Stucco Replacement – A Costly Undertaking

Stucco has been in existence for more than a thousand plus years. A modern stucco mixture consisting of sand, Portland cement, water, and lime creates an exterior building surface which is durable and requires little maintenance. In-and-of-itself stucco is an excellent choice as an exterior building surface.

 

So why do we have such an widespread issue with a building material that is so tried and true? The one word most associated with the majority of stucco issues in modern construction is installation, or more properly two words – improper installation.

 

Stucco itself is not a problem, the methods and shortcuts used to install it have become a big problem.

 

A traditional hard coat stucco is typically applied in three coats, the scratch coat, brown coat, and a final top coat. The stucco is applied onto a wire lath which in turn covers a weather/moisture barrier, such as felt paper that is installed on the exterior sheathing of the home. Sounds simple enough – so what is the problem?

 

There have been numerous studies as to why homes built in the past 20 years with stucco exteriors are experiencing such a high degree of moisture related problems, and the majority of issues stem from one or more of the following issues:

 

– Improper flashing of windows, doors, and roof lines.

Flashing refers to an impervious material which is installed to prevent the passage of water into a building from an angle or joint in the structure. Improper or lack of flashing and sealing can result in water leaking down behind the underlayment material and into the sheathing surface. Rather than repel water, incorrect flashing can actually channel the water into the wall cavity.  A notable missing component known as “kickout flashing” is often observed in homes with stucco related moisture issues. A kickout flashing is an angled piece of metal installed at a roof/sidewall intersection to divert water away from the wall surface.

 

Whenever stucco meets a dissimilar surface such as a window frame, care must be taken to allow for the difference in the expansion and contraction properties of each surface. If not sealed with the proper material this joint creates a gap through which water will penetrate. It has been observed that in homes with major moisture damage, exterior walls with no windows or openings in the wall surface, generally sustain little or no damage, when compared to their counterpart walls with windows and doors.

 

 

Moisture damage caused by an improper stucco installation to a home can go undetected for a long period of time. A telltale signs of a moisture issue can be found around windows where dark streaking is present at the corners of the window, which can indicate the deterioration of wood surrounding and behind the window, but in many cases there are no visible signs of moisture damage.

 

The use of infrared cameras to detect the presence of moisture in interior walls is an option, but can produce unreliable results. The definitive method to determine if there is moisture intrusion to the building is to perform what is know as an invasive moisture test.

 

An invasive moisture test involves the drilling of 1/4″ holes through the stucco surface at suspect locations. A moisture probe is then inserted into the hole through the wall to the exterior wall sheathing. Readings are interpreted to determine if there has been any damage to the wall surface. The holes are sealed after the readings are taken. This method of testing is not inexpensive, but well worth it when considering the extreme cost of full home stucco replacement.

 

If you are considering buying a stucco home, especially one that has been constructed in the past 20 years or so, make sure you do your due diligence. Not all homes with stucco exteriors have issues, but be prudent and start with a qualified home inspector who can counsel you on the next steps to take if further stucco evaluation and testing is applicable.