What would cause long horizontal lines of brick mortar to fall out?
Wednesday, July 11, 2018
Although there are a number of different defects that can cause brick mortar joints to fall out, if only the horizontal mortar joints are dropping and not every horizontal joint is having the problem, it is likely due to corrosion of brick “ladder” wire reinforcement. It’s called ladder reinforcement because the simplest version resembles a ladder, like in the photo below, although other designs have diagonal wires or mesh. Embedded ladder wire reinforcement in the mortar joint strengthens the wall in the same way that steel bars reinforce concrete.
Ladder reinforcement is offered in varying levels of corrosion resistance, starting with stainless steel and heading downward to basic galvanized. When corrosion begins—and corrosion of steel is a slow, but powerfully expansive process—the rusted steel gradually pushes out the mortar. Because the ladders are typically installed several courses apart, one of the ways to recognize this defect is that the distress occurs only on specific horizontal courses spaced equally apart, like in the photo below, of an entry wall at a residential development.
If the ladder corrosion is advanced, you can easily see the corroded steel wires in the strips of missing mortar.
In the early stages, the mortar is still in place but slightly pushed out.
Because moisture accelerates the corrosion, once the joint begins to open and lets rain water in, the process speeds up.
A similar defect in concrete, caused by rust of reinforcing steel bars, is called spalling. To learn about concrete spalling, see our blog “There’s cracks running along the home’s concrete tie beam. What’s wrong?”
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To learn more about exterior walls and structures, see these other blog posts:
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