Q: Several years ago, we had our front steps rebuilt. The treads and risers are brick, and shortly after construction we noticed a white substance leaching out of the mortar.
We scrubbed at it vigorously and eventually used diluted muriatic acid. Nothing worked, including hand and powered wire brushes, a cold chisel and full-strength muriatic acid. Do you have any ideas?
A: You’ve heard the saying, "Keep your powder dry." We want to tell you to keep your mortar dry.
Efflorescence has been the bane of masons for centuries. Unfortunately, there is no surefire fix. But we can give you a couple of ideas to explore.
Water-soluble salts and other minerals that migrate to the brick’s surface cause efflorescence. Brick is porous and will conduct water. As the salt-laden water evaporates, it leaves white stains. Initially the stains are soft and can be removed with a good wire brushing. In time, the salts crystallize.
Three conditions must be present for efflorescence to exist. There must be water-soluble salts somewhere in the steps. There must be sufficient water in the steps to render the salts into a solution. And there must be a path for the water to migrate to the surface, where it evaporates.
There’s not much you can do about the presence of salts in the structure. But you may be able to identify a source of water and the pathway that it takes to the surface.
There are two things we want you to check out. The first is simple. Try to keep surface water away from the steps. You can’t do much about rain, but if your sprinklers are soaking the bricks, you can redirect them.
Second, take a crawl under the house and see if the foundation of the steps is concrete. If so, note whether the concrete touches bare earth. If the concrete is in contact with the ground and there is no plastic vapor barrier, ground moisture may be wicking up through the concrete into the mortar and evaporating. Break the chain of water infiltration and you eliminate the efflorescence.
If you’re able to isolate and eliminate or reduce the water source, the next challenge is to remove the crystallized efflorescence. There are three options: chemical cleaning, sandblasting or pressure washing.
We’d give pressure washing the first shot. It’s more eco-friendly than chemical washes and less destructive than sandblasting.
We’d go the chemical route next. We know you’ve tried muriatic acid, but we believe there are stronger cleaners available to the trade.
We’d try to avoid sandblasting. The sand will pit the surface of the mortar, make a mess and require that the porch be sealed to stop surface water penetration.
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