The typical two story central Florida production home has two separate stucco systems installed on the home. On the first floor, the stucco is plastered directly to the concrete blocks. As they are both masonry materials, they bond together very well and are essentially trouble free with an extremely long lifespan. This is the most desirable structure and siding available. If water leaks in through cracks, the block soaks it up like a sponge and holds the water, which evaporates to the drier interior air. Usually, small cracks are not problematic, but during extreme rainfall conditions, the wall can become saturated and leak water to the interior. We rarely see this, as it takes a lot of water.
The second story walls are stucco on wood frame. Here the stucco is plastered over wire lath on top of water resistant layers. This is an entirely different system which can be problematic.
The stucco itself is essentially waterproof. Water leaks in through cracks and gaps between stucco and other penetrating elements such as windows. This leakage can penetrate the water-resistant layers and damage wood framing.
Even if water never gets to the wood, the water will cause the wire lath to corrode. When it corrodes, it expands and causes more cracking.
It’s essential to seal any cracks or gaps on stucco on wood frame. If you don’t, you can expect additional damage which may be costly. Do not minimize the significance of cracks in stucco on wood framing. Ignore anyone who tells you they are “just cosmetic.” They are not. They are the primary cause of damage to wood frame-stucco walls. Examine the stucco every year or so and repair any new cracks that develop.
So why do we build homes this way? Because it’s cheaper. The mantra in construction seems to be “cheaper is better.”