"Efflorescence is a whitish mineral deposit often seen on the interior of foundation walls," notes Ontario registered home inspector Michael Lau on his web site. "It forms on basement walls as water migrates through and evaporates, leaving minerals behind."
Basement water damage from efflorescence is one sign of a foundation moisture problem, but efflorescence alone does not indicate whether the problem is severe or active.
How Efflorescence Forms
As water passes out of or through concrete or masonry, it carries dissolved minerals. These minerals may be dissolved in the groundwater before it penetrates, or may be leached from the concrete.
When they reach drier inside air, the water evaporates, leaving the dissolved minerals to accrete (build up) in fluffy crystalline "blossoms".
The process of efflorescence is similar to the formation of tufa from groundwater, travertine in hotsprings or stalagmites and stalactites in limestone caves.
Efflorescence and Humidity
It is easy to assume that the greater the efflorescence, the more severe the moisture problem in the basement. This is not necessarily the case, as efflorescence formation is affected by
- The rate of water penetration
- The concentration of dissolved minerals
- The humidity of the inside air.
Faster penetration, higher concentration, and drier inside air will all produce faster or greater accretion of efflorescence. So a homeowner who uses a de-humidifier to dry out a damp basement will actually increase the efflorescence.
Other Signs of a Basement Water Problem
Efflorescence suggests a water problem that may have occurred in the past or that may be active and current. The prospective home buyer can watch for these additional signs:
- Patches on wall and floor – may also indicate cosmetic crack sealing without moisture
- Rust – rusted nails or screws in plasterboard or paneling, rusted electrical boxes, or rusted feet on appliances
- Mold or mildew – Stains from mold or mildew or the active presence of fungi
- Odor – Often accompanying mold/mildew
- Discolored or damaged finish – water stains, crumbling plaster or drywall, peeling paint, crumbling concrete
- Lifting floor tiles – these may be pushed up by efflorescence or by water-dissolved adhesive
- Rotted or discolored wood
- Items stored on skids or boards
Lau points out that these signs may be due to a one-time flood rather than an ongoing problem and advises discussing the matter with the homeowner.
Preventing Water Damage in Basements
Before calling a water damage service contractor to dig everything up to install interior or exterior weeping tiles, Lau suggests that the homeowner first consider simpler and less expensive methods:
- Ensuring gutters are sound, and replacing them if necessary
- Directing downspouts away from the home, adding extensions, etc.
- Examining surrounding ground for surface water flow towards house
- Regrading (positive grade 1" in 12" for six feet away from house)
- Sealing interior leaks
If these methods eliminate water access to the foundation, less water penetration will occur, and previous damage can be cleaned and corrected.
Fixing Efflorescence Water Damage
Canada's Shell Busey, on his weekly HouseSmart radio show, advised a listener on how to deal with water damage from efflorescence once the possible sources of water infiltration have been controlled.
- Wash the powder up with T.S.P. (trisodium phosphate) and rinse well.
- Acid-wash the concrete with a solution of 5 parts water to 1 part muriatic acid (follow safety instructions). Rinse and allow to dry.
- Using a low pressure garden sprayer, apply 2 coats of solvent-based concrete sealer such as Evercrete following product directions. Ventilate well. Allow to dry before replacing or installing floor covering.
Busey concluded as always with his trademark phrase, "It’s just that easy. "
References on Efflorescence:
- American Geotechnical – a good discussion of Soil Moisture
- Busey, Shell – Shell offers numerous tips and articles for taking care of leaky or damp basements, waterproofing, etc. on his House Smart site.
- Lau, Michael, MW Home Inspections Ltd – See the sections on moisture, wet basement, and condensation.
Thomas Alan Gray - Tom has been writing for over 30 years; curiosity leads him to dig into a wide variety of topics.
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