Surface efflorescence on ceramic tiles is not a flaw

Recently another tile manufacturer asked us to review a claim of defective tiles.  

The pool owner's representative was making an assertion that the ceramic tiles on the top of a spa dam wall were defective, as the glaze was changing colors due to UV and chemical exposure.

Tiles at tile of installation (click on image to enlarge)

Tiles after repeated wet/dry cycles (click on image to enlarge)

 
After reviewing the images of the tiles, immediately following their initial installation and present day, it became readily apparent what the cause of the discoloration was.

Efflorescence (or mineral build up) is not considered a defect.  It is a due to the lack of routine removal of mineral build up.  Much like the waters spots that form on dishes or glassware in a dishwasher, this mineral build up does not mean that the dishes or glassware are defective.  Some efflorescence may be coming from the grout or thinset.  But in any case, the tiles are not defective.

Special cleaning services are available that will remove calcium and mineral build up.  Most pool service companies offer these services at an additional charge.  Routine weekly brushing of the tile will not prevent mineral or calcium build up, so the pool service is not to blame either.

As the water evaporates, it leaves a film of minerals behind.  Over time these minerals begin to make the tile appear hazy white.

Some white efflorescence is even visible in the grout joints, before the pool was even completed.

The solution?  Pay someone to remove the mineral build up.  It's a maintenance issue!


Paolo Benedetti, SWD, Principal
Aquatic Technology Pool and Spa
www.AquaticTechnology.com
 International Swimming Pool Consulting and Design, Aquatic Consulting, Watershape Consultants, Expert Witness, Hydraulic Design, Landscape Architecture, Construction Management
Office: 408-776-8220
 Email: info@aquatictechnology.com
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Infinity & Vanishing Edge Pools - Preventing Leaky Weir Walls

Infinity and Vanishing Edge Pool Walls - Stopping the drips

I've had a number of requests for the addition of some graphics to help readers visualize the infinity edge weir wall and basin relationships.

The graphics will be hand drawings and not our usual computer drawings.  It is our intent to help you understand the concepts and not to provide a "cut and paste" work product on the Internet.

Where does the waterproofing go?

Since the vanishing edge wall is in effect a freestanding dam, it makes sense to incorporate waterproofing within the cement of the wall.  No matter what remodeling or work occurs in the future, there will always be that non-corruptible layer of protection.

I specify an additional layer of protection on the both surfaces of the wall, as well as inside the entire basin.  Any tile or stonework on the "dry side" of the vanishing edge wall or lining the catch basin, should extend down and into the minimum operating level of water that always remains (MOL).  Because the water level in the basin is constantly changing, the walls above the MOL are subject to constant wetting & drying.   Therefore any plaster based finish will be subject to shrinkage cracking.

The yellow highlighted area illustrates the minimum areas that should receive a topical waterproofing.  I prefer an elastomeric membrane topped with a compatible skimcoat of thinset (products from the same manufacturer).  This will ensure that the plaster will bond on the inside of the pool.  This membrane also prevents any moisture from intruding into the wall, since plaster is not waterproof.  Yes, you read that correctly, plaster is not waterproof.  It is after all, just cement and sand - and water does wick through cement based products.

 The yellow highlights indicate the minimal areas of waterproofing required.

Which way to tilt the weir?

It is a matter of preference.  I prefer to tilt the weir down and into the pool.  It creates the illusion that the pool is slightly larger than it actually is.

It is a fact of physics that water will always seek level.  It is also true that water will migrate via capillary action through cement.  If no waterproofing is employed on the vanishing edge wall, then water (2 large arrows on left) will quickly begin to seep through the mortar bed (green).

No matter which way the weir tilts, since the water level in the pool is higher than the potential exit point on the dry side, hydraulic pressure (weight) and gravity will force the water to pass through the mortar.  Left unchecked, over time the water in the pool would equalize with the exit point on the dry side of the wall (indicated by the blue line & double headed arrows to the right of the weir). 

Purple -  Granite tiles/slab
Green -   Mortar leveling bed
Pink -     Interior plaster/tile finish
Yellow - Dry side VE wall tile
Blue -     Water & migration paths
Blue Line - Equalization level

The water then migrates through the mortar bed, behind the dry side tiles.  As the water discovers cracks in the grout, some exits carrying with it dissolved salts (efflorescence).  The water will continue to flow through this mortar or in hollow areas behind the tiles, until it either encounters a dense area of mortar or a sound area of tile.  The remaining water will exit at this lower elevation, carrying with it a majority of the dissolved salts (hence a greater build up of efflorescence). (see the prior article on efflorescence).

By incorporating waterproof additives into the mortar bed, one can effectively seal the capillaries in the mortar, thereby retarding water migration.  The addition of a membrane a top the mortar bed, only leaves the layer of thinset (under the granite and tiles) as a possible migration path for the water.

Disclaimer:

The reinforcing shown in the drawings is not intended to represent the actual steel schedules one would utilize.  Instead, they are shown so that you understand how this all goes together.  However, the actual vanishing edge wall should never be less than 12 inches thick with double curtains of steel.  The exact wall thickness, steel size, spacing and placement is determined by the structural engineer.

The catch basin elevations were drawn arbitrarily.  Based upon a projects needs, the catch basin could be above, below or even with the pool floor.  The catch basin could even cantilever in mid-air.

Deepened keyway footings are shown in a drawing, but not every vanishing edge pool requires them.  Some require more elaborate foundations and others no specialized foundation.  The geotechnical engineer will outline this in his soils report for the structural engineer.

Paolo Benedetti - Aquatic Artist
"Creating water as art."™
Aquatic Technology Pool and Spa
©www.aquatictechnology.com

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
©www.aquatictechnology.com

Negative Edge, Vanishing Edge, Infinity Edge Pool Weirs & Walls

Paolo Benedetti discusses Negative Edge, Vanishing Edge, Infinity Edge Pool Weirs & Walls, design and construction considerations and the realities of routine maintenance vs. construction defects.

The Weir - The point of spillover...
The "weir" is the actual crisp edge that the water spills over. The material and design details that comprise this edge are critical.

Ceramic tile is the least forgiving when installed as a weir. The greater the variance in the surface of the tile & grout joints, the more water will be required to flood the edge. This also requires that the installer be "dead on" with their installation. Water will ALWAYS sit level inside the pool. If the tile is not installed level, the water will be a dead give-away!

I prefer to use polished natural stone. Though our specifications call for +/- 1/32" (a total of a 1/16" difference between highs & lows), natural stone can be further polished to ensure absolute perfection.

The grout joints will also contribute to variances in the weir elevations. Wider grout joints tend to have greater variances in their depressions. Additionally, they have a higher incidence of cracking.

NOTE: GROUT WILL CRACK - so, cracked grout, in and of itself is not to automatically be considered a construction defect!

Flowrates - low & slow is the goal!
The backside of vanishing edges are not supposed to be grand cascading waterfalls. Actually, the designer's goal is to flood the edge(s) using as low of a flowrate, and therefore as little energy, as possible.

This is not to say that they cannot be designed to be cascading waterfalls. However, if the owner desires a "waterfall" effect from the vanishing edge wall, then additional expenses and costs will need to be factored into the project.

A waterfall effect will require a material or weir that causes the water to break tension from the wall. It can be a simple change in the weir detail to create a large cascade effect. Or, an irregular material (e.g. ledger stone) can be installed on the outside face of the vanishing edge wall, to cause the water to splash free from the wall.

The cascading effect will require additional pumps & plumbing. Both effects will require a wider catch basin, as the splashing water will easily clear the width of a normally sized basin. Depending on the height of the vanishing edge wall, the width of this basin can be substantial. All of this translates to an additional project cost.

Choice of Veneers
What ever material is chosen to veneer the outside face of the vanishing edge wall, special construction techniques must be employed. Since the vanishing edge wall is in effect a giant dam, waterproofing is paramount. The waterproofing program should begin with the concrete itself and then include additional layers of protection as construction progresses. A competent
designer or builder will be intimately familiar with the options available.

The installation of the veneer material will require movement joints throughout the material. This means color matched caulking joints both vertically & horizontally through the material. Since this surface is repeatedly put through wet & dry and hot & cold cycles, the material must be able to expand & contract with these extremes. Failing to provide these joints will cause the material to crack or delaminate.

Efflorescence - French for "to flower out"
Whenever you have wet cement surfaces exposed to air, you will get efflorescence. It is a chemical reaction of the salts within the cement products hydrating & leeching towards the surface. The more the surface is subject to wetting & drying cycles, the greater the efflorescence to be expected.

Any cement product can contribute to efflorescence - concrete, mortar, thinset & grout. Even the labels on epoxy grouts contain a disclaimer about efflorescence.

There is no easy solution to preventing efflorescence. The key is to control the migration & penetration of water into & through the cement products. I say "through," because concrete contains microscopic capillaries through which water can migrate. There are chemicals and processes to control the water migration and saturation. The specifications just need to be defined and included in the project specifications - and, yes, they do add to the cost.

So, the presence of efflorescence is not a construction defect. It might indicate that the designer or builder did not include a waterproofing & migration control program (which you probably did not pay for either). This will result in the unsightly development of efflorescence and reoccurring maintenance expenses to remove it.

The caulking joints will also require periodic removal and replacement. The frequency of the maintenance of these joints will depend on the wall's exposure to the sun, temperature extremes, proper installation & joint preparation and the veneer materials. Materials with a high expansion index will place greater stress upon the caulking (mastic).

If you hire a knowledgeable designer & specifier, they can discuss the additional costs, help you weigh the maintenance and cleaning costs and the negative long terms costs and ramifications of not taking these simple precautions.


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