Why is stucco that goes into the ground a problem at a wood frame house?
Tuesday, October 27, 2020
Builders extended stucco right into the ground at many Florida homes that were built until about the 1990s. Due to the problems we are about to describe, it was gradually replaced by stucco that stops within 4” to 6” above ground. Then, in the last 20 years the gap between the ground and the bottom of a stucco wall finsh became a code requirement in Florida, along with a weep screed for drainage at the bottom of the stucco.
The primary reason for this is termite protection. Stucco that is applied over a wood frame wall must have a separator sheet behind the steel wire mesh that acts as a the base for stucco application and the wall below. There are invariably ribbons of very narrow space running up behind the stucco. but not too narrow to keep tiny termites out. Two termites fit easily on the head of a match.
That space has been called a “termite super-highway.” It enables them to enter the wood walls and begin consuming them, eating all the way up and into the attic, without being observed. The gap of exposed concrete slab near the ground creates a “no man’s land” that they must cross to get at the wood of the house. Because termites are extremely moisture dependent, they cannot cross it without creating tell-tale mud tube tunnels to protect themselves from the dry, open air. These tubes are one of the things that termite inspectors search for, and a homeowner that knows what they look like can too.
Stucco below grade also wicks moisture up from wet ground. And in Florida, where the ground is wet for a good part of the year, this is another problem. It corrodes the steel mesh and rots the plywood behind it. Here’s an example of a simulated brick stucco finish that is failing due to long-term capillary action pulling water up into it. As the wall cracks, more water gets in.
And the third issue is that most pest control companies will not issue a termite bond on a house with stucco below grade. It’s too risky. The stucco can be repaired by a professional contractor that cuts it away to a few inches above ground, but it is a tedious, labor-intensive, and expensive process.
All of this is why we call out stucco below grade as a defect in our inspections of wood-frame-homes with a stucco wall finish. Yes, we know it was acceptable at the time the house was built, but that doen’t make it any less of a problem today.
Stucco below grade at concrete block houses does not present the potential for a termite problem, but can can sometimes elevate the moisture in the block wall behind it. We do not consider this a defect unless there are visible moisture problems. New block homes today also stop the stucco a few inches above grade with a weep screed for drainage.
See our blog post Why is my stucco cracking? to learn more.
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