What causes the discoloration of bricks?

“Brick red” is a common color name for a reason: it’s what we expect from our bricks. We’re used to seeing tall buildings with long, unbroken stretches of red masonry.

That all changes when those bricks start to discolor.

When you look at older buildings that haven’t been maintained, you might see walls covered in white, green, or brown stains, hiding the beauty of the old brickwork. What causes this discoloration? And how do you fix it?

Causes of Brick Discoloration

Brick discoloration shows itself in several different ways depending on the cause.


You’ve probably seen white deposits on a brick wall before. These are known as “efflorescence” and come from moisture inside the wall traveling to the surface, bringing salts in the brickwork along for the ride. You can replicate this at home if you put saltwater in a glass and let it evaporate — the salt will leave white deposits on the glass.

The color of the efflorescence can change depending on the chemical structure of the brick and mortar. Sometimes there are other chemicals in the salts, which can lead to green or brown discoloration instead of white. Efflorescence isn’t usually a structural issue.

Algae, Mold, Moss, and Lichen

The discoloration on your brick walls might not be chemical — it might be living. Algae, mold, moss, and lichen can all find a foothold on brick and mortar. These living organisms will discolor the wall, and even after they’re washed away, they may leave evidence that they were there.

This occurs most commonly in areas that stay moist, particularly in moist climates. It may be an indicator of a drainage problem.


Rust stains aren’t common, but you may run into them occasionally in areas where bare metal was exposed to the elements and water ran off down the brick. This often occurs with things like window grates or window unit air conditioners.

Discoloration is usually a cosmetic issue, not a structural one. But there are times it may point to a deeper issue. If you have any questions, contact us, and we’ll come out to give you a consultation.