Tile and Masonry Efflorescence - An unavoidable cancer

Efflorescence is virtually unavoidable in construction that includes cement products that are exposed to water.  Place these materials in water or run water over them for hours each day and you are bound to develop these white crystalline growths.

Construction Defect?
Well, not exactly... and maybe so.  Why the ambiguity?  While efflorescence cannot be totally eliminated, sound construction practices can surely reduce it's development.  Sloppy and lazy construction practices that do not employ protections from moisture intrusion are to blame for most cases of severe efflorescence.

Understanding the Cause
Clients always complain about the development of efflorescence.  Many mistakenly see the efflorescence as an indication that something is leaking.  In most instances, the moisture is not migrating through a structure for the efflorescence to develop.  The water is merely saturating the surface and activating the salts.

Most efflorescence develops from moisture that penetrates through the grout, cracks in the grout, stucco or mortar.  This water can be from irrigation, rain, or merely water spilling over a vanishing edge wall.  Once the water gets under the surface veneer, whether it be tile, stone, stucco or plaster, gravity takes over.  The water will flow down behind the veneer until is reaches a point of maximum saturation or a point where the veneer is soundly attached.

At this point the water will work it's way towards the surface that offers the least resistance.  As is does, it activates the salts in the cement products.  These salts can be chlorides, sulphates or bicarbonates.  These little crystals travel in the water, and as the water dries, the crystals harden.  Just like the hard water spots on the glasses in your dishwasher.

As these salts dry and harden, they develop a white salty crust, or efflorescence.  Since it is a chemical reaction between the cement products, water and air, the development of efflorescence will eventually stop.  But when it will stop is any one's guess.  It may continue for decades.

 An Ounce of Prevention...
Since all cement products require some calcium, that component of the equation cannot be eliminated.  Keeping air away from the cement products is virtually impossible.  That leaves the management of the intrusion of water.... preventing the water from entering the cement and activating the calcium salts.

Most property owners hire contractors based upon their bids... the bottom line.  And these "bottom line" guys are not including the safeguards and measures required to minimize the development of efflorescence.  You can't have it both ways.... pay for the prevention or live with the consequences (sounds a a lot like a talk my dad had with me as a teenager).

Stop the Migration
The prevention of moisture migration begins with the structure.  Cements can be fortified with a variety of additives that can make the cement denser, activate the calcium salts or close the microscopic capillaries that allow water to dampen the cement.  Manufactured cement products such as mortars can also be fortified in this manner.

Concrete based building materials, such as CMU blocks, prefabricated concrete panels or tilt-up walls can be sprayed with penetrating chemicals that react with these salts, binding them to the cement.  This prevents water from activating the salts and creating efflorescence.  The resulting matrix of the concrete is oftentimes water resistant as well, as the capillaries have been closed up.

 Surface barriers that prevent water from entering the concrete can also be applied to the concrete structure.  These barriers can be cementitious, clay, petroleum or latex based products.  The more flexible the barrier is, the more it will be able to span small fissures and cracks in the underlying concrete structure.

Misconceptions
Even structural engineers do not understand the principals behind efflorescence. Many see efflorescence and immediately assume that a vessel is leaking.  However, the totality of the situation must be investigated.

If the exposed side of a vanishing edge wall is developing efflorescence, I would not immediately jump to the conclusion that the wall is leaking.  Since the wall is saturated for 2-4 hours per day, the tile is in effect flooded with water.  The water infiltrates the grout and the underlying thinset.  When the water stops flowing, the water begins to evaporate & the crystals begin to activate.  If the water level above the wall did not show signs of loss (a bucket or dye test), then the wall is probably not leaking.

A keen indication of this, is if there are vertical indications of efflorescence.  These will usually follow hairline cracks in the grout or tiles.  As the water evaporates from these small fissures, efflorescence also develops.  The heaviest build up of efflorescence will usually be at the bottom of the fissure, or the point where the water met resistance to further downward flow.  At this point, the water can only go outward towards the surface... bringing with it efflorescence - and hence the heavier build up.

Most of the time, the lack of expansion joints on these large expanses of tile causes them to delaminate from the wall.  The hollow space behind the tiles is a perfect freeway for the water to travel on.  Tapping on the tile with the handle of a screwdriver will identify hollow sounding areas of delamination.

The water usually enters through small cracks at the top of the wall & travels behind the tile through these delaminated areas.  Large layers of mortar a top the vanishing edge wall can also allow water to migrate across the top of the wall & leak behind the tile veneer.

If the water was leaking through the wall, cracks would be clearly visible on the water side of the wall.  Additionally, if the water was migrating through the wall, then iron oxides (rust) would be visible as well from the corroding reinforcing steel.  Saline pools would experience an accelerated level of corrosion from the presence of the salt water.

Use High Quality Materials
Besides subscribing to a waterproofing program prior to and during construction, one must utilize high quality materials.  Mortars that are site mixed by masons seem to be the worst offenders.

Factory mixed and bagged setting materials undergo quality control inspections as to their blend, particle sizes and purities.  Generic home improvement store brands do not perform as well as name brand products with warranties.

While these extra measures cannot guarantee that a project will not develop efflorescence, they will minimize the effects and reoccurring maintenance associated with cleaning efflorescence from the surface veneers.  The results are that the surface veneers will look better and last longer, as they will not be subject constant aggressive cleaning chemicals, acids and abrasives.

Even epoxy grouts contain a disclaimer against the development of efflorescence.  The epoxy compounds only replace a portion of the cements... therefore the remaining cements (with lime/calcium salts) can develop efflorescence.


Paolo Benedetti - Aquatic Artist
"Creating water as art."™
Aquatic Technology Pool & Spa
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