Permission granted by InterNACHI
The term "stucco" is used to describe a type of exterior plaster applied as a two- or three-part coating directly onto masonry, or applied over wood or metal lath to a log or wood-frame structure.
In the inspection image below, there is a large open crack at the outside corner near the downspout.
Most stucco deterioration is the result of water infiltration into the building's structure, either through the roof, around chimneys, window and door openings, or excessive groundwater or moisture penetrating through or splashing up from the foundation.
Potential causes of deterioration include:
ground settlement lintel and door frame settlement;
inadequate and leaking gutters and downspouts;
moisture migration within walls due to interior condensation and humidity;
vapor drive problems caused by the furnace, bathroom, and kitchen vents; and
rising damp resulting from excessive groundwater and poor drainage around the foundation.
Water infiltration will cause wood lath to rot, and metal lath and nails to rust, which eventually will cause stucco to lose its bond and pull away from its substrate.
Check stucco for cracks, crumbling sections, and areas for potential water intrusion. In the inspection image, the inspector is observing the area above the window where the stucco comes in contact with the window frame. Old and weathered cracks may be caused by the material’s initial shrinkage or by earlier building settlement. New, sharp cracks may indicate movement behind the walls that should be investigated further. Stucco can be cleaned. It can also be painted.