How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
site-built, mobile/manufactured and modular homes
What causes brick stain or discoloration near the ground?
Tuesday, June 14, 2022
The culprit is almost always high moisture content in the brick, especially at the face. And the specific delivery system of the wetness could be 1) sprinklers hitting the wall, 2) rain rolling off the edge of a short roof overhang with no gutters and splashing back onto the wall, 3) a plumbing leak, or 4) moisture rising up from wet ground—being wicked upward by capillary action (rising damp).
If the color is dark green or black and the surface can be scraped off, then it is a fungal growth. A white powdery surface means it’s efflorescence, which happens when the salts in the brick become wet and get pulled to the surface, then dry. See our article What are those powdery white areas on my brick walls? for more on this phenomenon.
Other colors, such as yellow and red ochre, are also the result of dissolved minerals migrating to the surface and drying into powder. Rust from reinforcing steel ladders in the mortar joints can also cause staining and cracking along the mortar line. Go to What would cause long horizontal lines of brick mortar to fall out? for more details.
Rising damp occurs when there is no water-stop material between brick courses, such as a metal or lead flashing, near ground level to stop the upward movement of moisture coming from the soil. In some cases, it can cause brick to disintegrate and crumble away. Read our article What causes the surface of old bricks to erode away into sandy powder? for photos and details.
Examples like the one shown at the top of the page are most likely a comabination of sprinkler overspray and rising damp.
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