Efflorescence refers to crystalline salt deposits that often appear on building surfaces or masonry materials. It’s made up of salts that are left over when water evaporates from porous construction materials.
The salts that form appear as a white or greyish tint residue on floors and walls. Efflorescence can be indicative of a cosmetic problem or an internal structural weakness. Either way, this unsightly deposit can be a vexing issue if it appears without warning.
What Causes Efflorescence?
Water comes from a concrete mix that’s too wet and carries the salts to the surface of masonry materials. Other sources of unwanted moisture include underground seepage, sprinklers, and roof runoffs.
Water carries dissolved salts through capillaries in concrete, brickwork, mortar, and masonry to the surface. A combination of high material density and fewer channels makes it more difficult for salty water to reach the surface.
Seasonal weather changes also influence the appearance of efflorescence. For instance, low humidity accelerates water evaporation and this means salt deposits remain unseen. High humidity levels slow down the evaporation, thus increasing the likelihood of deposits. The risk of efflorescence is higher after heavy or consistent rains as opposed to dryer summer months.
Soluble salt, water, and channels all have to be present for efflorescence to occur. Some of the common salts in masonry materials include ordinary table salt, sulfates, and silicates. Alkalis like calcium hydroxide can also form salts when exposed to air. The sand and gravel used to make concrete, patio blocks and mortar contains natural salts or salt-forming chemicals.
Primary Vs. Secondary Efflorescence
Primary efflorescence occurs during the initial curing of cement. It is also known as new building bloom and appears during the first few weeks or months after construction as the water used during construction evaporates. Normal weathering removes primary efflorescence and it doesn’t reoccur.
Secondary efflorescence is more persistent and due to the influence of external concrete poisons. For instance, the presence of road salt leads to the formation of saline solutions that dissolve into the concrete garage floors. It can occur at any time and – unless the moisture problem is resolved – will continue to escalate.
How to Remove Efflorescence
Although there are several solutions to remove efflorescence, addressing the root problem is the only way to ensure efflorescence won’t reappear. The solutions below involve adding water to the concrete walls, and can make the problem worse, so proceed with caution. It’s ultimately best to call a foundation specialist first to determine the true cause of efflorescence.
A Simple Washing
You’ll want to try this approach when the deposits are still new as that’s when efflorescence is most soluble. Scrub it off using a mild detergent, water, and a stiff brush. Applying elbow grease can help remove stubborn deposits. Make sure you rinse thoroughly once you’re done. You don’t want the dissolved salts reappearing as efflorescence in a few months.
Pressurized water removes surface deposits quickly and effectively. Use the widest-angle tip that removes the residue without damaging the surface. If the spray is too intense, it could open up more pores and leave the brick more susceptible to efflorescence.
If pressure washing is not enough, acidic cleaners will dissolve the residue more effectively. Start by soaking the surface with water to prevent the cleaner from penetrating and opening up more pores. If using a proprietary cleaner, follow the outlined instructions explicitly. You can also use diluted citric acid, vinegar, and muriatic acid. Finish by neutralizing the acid with a baking soda solution and rinsing thoroughly with water. Be sure to wear protective goggles and gloves when handling chemical cleaners.
A general rule of thumb when removing efflorescence is to try gentle methods before progressing to more aggressive solutions.
How to Prevent Efflorescence
The best way to deal with efflorescence is to prevent it from occurring in the first place and this requires the intervention of a basement waterproofing professional. That said, here are a few measures you can implement to prevent efflorescence.
Incorporating overhangs, eaves, and a gutter system can go a long way towards ensuring water doesn’t get into the foundation or walls.
Make sure you have enough adequate runoff areas to direct water away from the house. Grading the yard away from the foundation, and moving flowerbeds that need constant watering from the house are a good start. If you have a sprinkler system, set it up to direct water away from the walls.
Installing a vapor barrier in the crawl space or basement will prevent the entry of moisture and salt absorption.
Waterproofing professionals use grout admixtures to improve grout flow. This reduces water content and porosity, effectively preventing the absorption of salts. Talk to your contractor before choosing this route.
While a normal by-product of masonry construction, efflorescence can be an indication of water intrusion. If you notice any flaky deposits, contact a waterproofing expert to get to the root of the problem and implement trusted basement or crawlspace solutions.