What causes a horizontal crack in a block or brick wall?
Wednesday, June 27, 2018
The horizontal cracks we see most often are near the ground level of concrete block stem-wall type construction. They are caused by rotation of the footing below ground, due to soil movement or a defect in the bearing below it. The wall usually turns outward along a mortar joint, like in the photo above. where the crack near the ground has been caulked but continues to open further. Heaving or sinking of a thickened-edge concrete slab foundation also causes a horizontal crack line, but usually higher on the wall, like in the photo below, in which the diagonal cracks show that the corner is sinking and the horizontal crack indicates the beginning of rotation.
Long horizontal cracks near the top of a wall are often actually in the concrete tie beam above the block, and caused by corrosion of the reinforcing steel just below the surface. It is called “spalling”.
Also, horizontal cracks can also appear along mortar joints in a brick wall when the steel reinforcing “ladders” begin to corrode and pop out the mortar.
To read more about these two problems, see our blog posts There's cracks running along the home's concrete tie beam. What's wrong? and What would cause long horizontal lines of brick mortar to fall out? Also, although crack patterns can often lead you directly to the underlying problem, sometimes a more in-depth analysis is necessary. See our blog post How do you analyze a crack from cause to effect? for more on this.
And we recommend reading our other posts How do I recognize serious structural problems in a house? and What are the places to look for structural cracks in a house? and What causes a vertical crack in drywall? and What causes stair-step cracks in a block or brick wall?
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To learn more about exterior walls and structures, see these other blog posts:
How To Look At A House
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