Find out what efflorescence is and how to remove, prevent it

Efflorescence is not a rock band. That’s Evanescence.

Efflorescence is the white, chalky substance that appears on concrete, pavers, brick, and stucco. It is residue that is left behind when hard, salty water evaporates. It can be caused by groundwater, which is notoriously hard in Arizona or caused by rainwater.

Common causes of efflorescence are irrigation sprinklers overreaching and watering the exterior of the house and patio constantly. It can also develop following a heavy rainstorm.

While it is typically a cosmetic issue, according to the International Association of Certified Home Inspectors, it can also be a sign of moisture intrusion that may represent a structural issue down the line. Once it appears, there are steps you can take to rid the surface of what could be deemed an eyesore.

Removal options will differ depending on the surface it has established itself, with concrete being a bit simpler to treat versus stucco.

Important: Before removing, confirm that the substance is efflorescence and not mold. Mold will typically only develop on organic substances, but it can feed off of dirt within cracks found on brick or concrete. A few simple tests can be done to determine what exactly it is. If you pinch the substance between your fingers, efflorescence will break down into a powdery substance, while mold will not. You can also take a glass of water and drop some of the substance into it. Mold will not dissolve. Efflorescence will. If you have mold, call a professional mold remediation specialist.

Removal from concrete, pavers and brick

There are different solutions depending on how hard you want to work. Sometimes the stains can be removed by simply washing them away with water. However, if they are stubborn, mix a solution of one part vinegar to five parts water before scrubbing it off with a stiff brush. You may also use a power washer to remove stubborn stains that water alone did not wash away. If you go this route, be sure to not exceed 1,000 psi.

Removal from stucco

Stucco can be a bit more involved. You need to be mindful about not damaging the stucco in the process. Similar to concrete, a power washer can be used. Again, do not exceed 1,000 psi for the water pressure. We recommend using a 40-degree fan nozzle and holding it roughly 15 to 18 inches from the surface. Be careful of flying chunks of material. Stop immediately if you see them. Lower the pressure and increase the distance from the wall before continuing. If stains remain, add diluted trisodium phosphate to the washer’s secondary pickup tube, which can be found at any home store.

Regardless of the surface, when removing efflorescence, wear protective eyewear. Small particles or even chunks of the surface can fly around and land in your eyes.

Prevention

Unfortunately, there is no way to completely prevent efflorescence from occurring, but you can limit its severity and frequency. The easiest way to prevent build-up is to eliminate sources of water from depositing on the surfaces on which it forms. This can involve changing the location of the sprinklers throughout your yard to avoid excess water depositing on the concrete or walls.

For stucco, use elastomeric caulking on any cracks you find. Seal gaps around windows, doors, plumbing fixtures and anything else that would allow water to get underneath the stucco.

Be careful to not caulk weep screed found at the bottom of the stucco.

Important: Do not cover the entire wall with this type of paint or caulking as they will trap moisture and create more problems. Consider priming the walls with an alkali-resistant sealer that will assist in neutralizing the efflorescence. Following the application of the primer, using a sprayer, apply a good amount of 100% acrylic paint, aggressively working the paint into the surface of the wall with a roller. A sprayer alone won’t ensure every nook and cranny is covered.

Join Rosie on the House every Saturday morning from 8 a.m. to 11 a.m. on KTAR News 92.3 FM. If you’d like to send us questions or comments, email mailto:info@rosieonthehouse.com. Follow us on Twitter and “Like” us on Facebook. For more do-it-yourself tips, go to rosieonthehouse.com. An Arizona home building and remodeling industry expert since 1988, Rosie Romero is the host of the syndicated Saturday morning Rosie on the House radio program. Call 888-767-4348 with questions and comments.