What is Stucco?
Stucco is a cement-based plaster that is applied over walls and other surfaces inside and outside of buildings. It is made from cement, sand, and lime and hardens into a highly durable material and can be used to obtain different textures and finishes. Stucco typically is applied over a galvanized wire mesh called lath, which helps the stucco adhere to the surface and strengthens the entire assembly.
Metal stucco lath is installed over a moisture membrane applied to the wall sheathing. The lath creates spaces of about 1/4 inch in depth to allow the stucco to squeeze into the spaces for a strong mechanical connection. Traditional, or “3-coat” stucco is applied over the lath in three thin coats: the scratch coat, the brown coat, and the finish coat. The scratch coat is applied first and is embedded into the metal lath to provide a strong base for the system. The brown coat is applied next to create an even surface for the finish coat.The finish coat is applied last, creating the decorative finish on the wall surface. The total thickness of the three coats is approximately 7/8 inch.
Dangers of Stucco
Stucco looks great on the outside of your home. However, if you live in a harsh climate that receives a lot of rain, humidity, or snow, stucco may do your home much more harm than good. Mold and rot issues can threaten the structural integrity of your home. Staining around the corners of windows, dark spots where a roof and wall meet and even visible cracks are indicators of possible damage. These stains are signs of where water runs on and/or within the stucco. Where you see these, moisture is likely behind the stucco, however, it is only through a professional inspection that a subsurface problem can be confirmed. Stucco problems are not limited to the exterior of your wall. There may be some hidden damage that you can’t see.
Water trapped within a wall can lead to mold growth within the wall cavity, possibly leading to health issues for the occupants. Once mold begins to grow, the only way to address it is to get a qualified contractor to open the wall, treat it, then put it all back together.
Over time, leaks that penetrate the wall can lead to structural damage. Many wood materials used today do not hold up as well to moisture as materials used 30,40,50 years ago. Rot could lead to serious structural issues within the building.
How to test for moisture?
The pin probe testing that we do involves drilling two small holes, using a 3/16” drill bit, about one inch apart through the stucco at each test site. We then insert the probes of a moisture meter into these holes and pound them into the sheathing material that is just behind the stucco. The sides of these probes are insulated to protect them from contacting the stucco or the metal lath fastened to the exterior of the sheathing. The moisture meter passes a small electrical charge between the probes and calculates the percentage of moisture, by weight, of the material being tested based on the level of conductivity. If a material is wet, it’s a better conductor and results in a higher reading.
What do the readings mean?
Any reading of 14.9% or less is considered normal in an exterior wall. A reading of 15-19.9% is elevated and indicates some leakage, rot is possible. A reading of 20% or more indicates excessive moisture, rot is likely to occur over time. Structural damage is possible.
Dealing with the Problem
You can get your home inspected for this type of damage and deal with it before it escalates. Discovering potential moisture problems early can save thousands of dollars in repair costs.
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