Steve Sargent

Joint issue: Guidelines by the Tile Council of North America state that movement joints should be placed every 8 to 12 feet apart or when there’s a change of plane, change of backing material or when the surface is abutted and restrained by another, such as under the coping, above. Their recommended width depends on their spacing and expected temperature differentials. Between rows of tile, a movement joint is created simply by placing a flexible sealant where grout normally would go. Under the coping, installers create a void going all the way back to the pool shell, place a foam backer rod or similar product, then top it with the flexible sealant.
Steve Sargent Joint issue: Guidelines by the Tile Council of North America state that movement joints should be placed every 8 to 12 feet apart or when there’s a change of plane, change of backing material or when the surface is abutted and restrained by another, such as under the coping, above. Their recommended width depends on their spacing and expected temperature differentials. Between rows of tile, a movement joint is created simply by placing a flexible sealant where grout normally would go. Under the coping, installers create a void going all the way back to the pool shell, place a foam backer rod or similar product, then top it with the flexible sealant.

These days, it seems contractors find themselves increasingly at odds with manufacturers of glass tile.

Take the example of Greg Andrews. One time, the widely respected veteran refused to install a particular brand of glass tile after soaking a sample in water only to find that the glue holding the mesh backing softened significantly within minutes, indicating that it wouldn’t perform in a pool environment.

“[The manufacturer] said, ‘No, it’s not an issue. Just install it,’ but they would never give me anything in writing,” says Andrews, owner of Andrews Tile based in suburban Los Angeles. “So I took a small sample, put it in a glass of water, photographed it and sent it to the manufacturer. They accused me of doctoring it up.”

Another time, the problem stemmed from a waterline installation where all of the tiles above the water’s surface were cracked, but those underneath were fine. When Andrews was called in to replace the original contractor’s work, the tile manufacturer contended the failure was due to a lack of movement joints. But the damage was identical in areas that wouldn’t have been affected by expansion, Andrews says.

“I said, ‘I disagree. There’s something else happening here,’” he recalls. “I got kind of a nasty letter back saying, ‘Your installer doesn’t know what he’s talking about.’”

Several more angry conversations took place, one at the manufacturer’s booth in the middle of a trade show. “We went back and forth, back and forth,” Andrews said. “I finally told the client, ‘I won’t install this material. If you’d like to choose something else, [I’ll be happy to work with you].’”

Glass tile is one of the most unique, stunning, and high-end materials used in pools and spas. It’s also sparking a lot of debate.

Many installers, including reputable professionals with decades of experience, are facing problems such as inexplicable delaminations and shattering of the tile, sometimes before the pool or spa has even been filled.

These issues can prove devastating to clients and the professionals who have to pay for corrections. “People have 2,000 feet of glass tile installed for $20,000, it all falls out and then costs $120,000 to take it out and put it in correctly,” says Scott Fleming, owner of Glass Tile Consultants and Scott Fleming Ceramic Tile in Carlsbad, Calif.

The problem has resulted in heated conflict between manufacturers and installers, with the truth all too often buried beneath finger pointing and a lack of clear, consistent data. Yet that hasn’t dampened consumers’ seemingly insatiable desire for the product — indeed, glass tile is more popular today than ever before.

“Almost every [glass tile] failure I work on gets replaced with glass,” says Fleming. “People love the product, and they have a vision of what it was going to look like.”

Interestingly, it’s the tile’s very popularity that’s partly responsible for these issues. A surge in demand for glass over the last decade has greatly increased the field of play, prompting new manufacturers and installers to enter the market and giving rise to questions about installation methods, types of backing and overall product quality.

The lay of the land

Traditionally, glass tile has been the highest of high-end products with a price point well over $20 per square foot. However, thanks to an influx of manufacturers entering the market, the product can now be found for as little as $3 per square foot. Moreover, the weak economy has spurred competitive bidding among installers, lowering the final cost to consumers even further.

But those savings come with a price. “People buy a material that is $25 a foot, then they [hire] a guy who charges $8 a foot, and [makes mistakes],” Fleming says. “The redos are hundreds of thousands of dollars sometimes.”

This is frustrating to many reputable, high-end tile manufacturers who don’t like to see their companies’ image tarnished by a recent increase in substandard product and practices.

“We’ve always been at a retail price point of $30 or $40 per square foot,” says Johnny Marckx, executive vice president of Oceanside Glasstile in Carlsbad, Calif. “When you can go to Home Depot and buy product for $5 to $10 per square foot, you can see that the market has shifted to include commodity products that can be of questionable quality for exterior applications.”

As the industry began its meteoric growth spurt, it also became apparent that there was a shortage of standardization and oversight. In answer to that need, in 2012 the American National Standards Institute released ANSI A137.2, a voluntary standard that sets parameters for testing and covers issues such as strength, resistance to chemicals, and thermal shock — a phenomenon in which instantaneous temperature changes cause cracks to form. The standard also addresses aesthetic concerns such as flaws and uniformity.

Professionals have high hopes that ANSI A137.2 will help weed out tile products not suitable for wet or exterior applications. However, voluntary standards are just that — voluntary — and can take years to enter the bloodstream of a product segment.

As a result, the glass-tile industry finds itself at a unique juncture, its use growing rapidly while the standardization of production and learning curve of many installers are only beginning. While a core group of reputable manufacturers and experienced installers has flourished for decades, it may take time for the system to catch up with the burgeoning demand and influx of new players.

As one tile veteran put it, “Caveat emptor.”

Movement joints

One topic at the heart of many heated debates between installers and manufacturers is the question of movement joints.

These gaps between materials (such as coping and tile, or two rows of tile) are areas where installers insert a flexible filler rather than a cementious grout. This is meant to absorb stress and allow space for the tile to expand and shift without cracking.

Yet because the material used to fill a movement joint is different from standard grout, the joints can create an undesirable visual break in the wall or floor.

An installation handbook published by the Tile Council of North America states that, in exterior applications, movement joints should be placed every 8 to 12 feet, when there’s a change of plane, change of backing material or an abutting surface. Many manufacturers specify that this be followed during installation of their product and, because glass tile is more sensitive to expansion than other varieties, they encourage installers to space the joints at the closer end of the spectrum.

“If the tile is exposed to a broad range of temperatures, there will be more expansion and contraction taking place,” says Ken McGregor, vice president of sales for Interstyle Ceramic & Glass Ltd. in Burnaby, B.C. Canada. “Provision must be made for that.”

Many manufacturers stand behind this requirement and are baffled that the joints aren’t put in place every time, considering that the TCNA recommendation is decades old and that glass is more sensitive to expansion than porcelain or ceramic. Without movement joints, they say, tile is made to perform in a way that was not intended.

“When [installers] don’t put in expansion joints or caulking joints and they don’t make that a floating plane ... they’re turning a decorative glass face into a part of the actual pool structure,” says Carl Steadly, president/CEO of Lunada Bay Tile in Torrance, Calif. “When it’s a floating plane insulated from the coping and shell, it’s great. When it’s taking the brunt of the forces from the pool shell and the thermal shock in the pool coping, it gets crushed.”

Indeed, there’s little argument among veterans that these joints should always be placed between the tile line and coping, but unfortunately this practice often isn’t completed in the field. “That’s the one place where I would tell anybody, at the very minimum, to put one,” Fleming says. “Yet, the majority don’t do that.”

Some will even grant that movement joints should occur in areas that see wet and dry conditions, such as the waterline and vanishing-edge weirs.

However, a number of installers, many of them veterans, question the need for the joints under water, where temperatures stay relatively consistent.

“The environment is controlled,” says Jimmy Reed, president of Rock Solid Tile in suburban Los Angeles. “It’s never going to be within 20 degrees either way in winter or summer. And let’s say you have a round or oval shaped pool. Where are you going to even put a movement joint in there?”

But other experts believe that this may not hold true in colder climates. The difference in temperature between the frostline and pool water could be dramatic enough to cause problems, Fleming says.

The need for movement joints under water may go beyond temperature fluctuations.

“If you just look at it in regard to hot and cold, then you’re missing the whole point of expansion joints,” says Christina White, general manager of Hakatai Enterprises Inc., a tile distributor based in Ashland, Ore. “It allows forgiveness for any type of movement. You think about the amount of pressure that’s on a swimming pool bottom — you have the water [and] that in itself is a lot of pressure. And if anything underneath moves, that’s going to shift around, too. So you’ve [got] water pressure, unknown substrate movement, and hot and cold.”

The movement joint controversy involves more than installation practices, inconvenience and aesthetic issues. Several installers claim the requirement is being used as an escape hatch for manufacturers — including those who make waterproofing agents, thinsets and other setting materials — looking to duck their warranty responsibilities.

“It’s a problem with vendors not standing behind the products when there are failures,” says Scott Cohen, president of The Green Scene Design & Construction in Los Angeles. “They need to learn about what happened, why it happened and how to avoid it in the future. [But] the manufacturers in some of these cases will blame the failure on the contractor’s installation method when in fact it’s a problem with the product.”

Andrews generally agrees. “There’s a lot of bad glass out there, and there are a lot of bad installers out there,” he says. “Manufacturers have really tried to defend themselves by using [the movement joint] standard, some of them rightfully so, but some of them have taken it to a level where they won’t accept any responsibility.”

Along those lines, while there are manufacturers that will serve as important educational resources for installers, others are more reticent to provide guidance.

“There basically is no one to ask,” Andrews says. “I can call a tile company and say, ‘Okay, Mr. Tech Support, I have this tile project. It’s a shotcrete pool, here’s the psi, here’s the steel schedule, here’s the geological report, here are the ambient temperature fluctuations, here’s the water temperature. Where should I put movement joints?’ “[They’ll say], ‘We can’t tell you.’ Yet when there’s a failure, regardless of the type, the expert will say, ‘I can see there are no movement joints,’ [and refuse to honor the warranty.] To me that’s a big issue.” But at the end of the day, many contractors agree that the movement-joint guideline should be followed for protection in case a lawsuit is filed.

Mounting issues

Another topic causing heated discussions within the glass-tile community is the question of mounting material.

While glass tile adds an almost other-worldly beauty to pools, it is legendarily difficult to install. Glass doesn’t absorb other substances — a plus when it comes to withstanding the chemicals or algae that can mar many finishes, but a challenge to those trying to adhere the tile to the shell.

For this reason, achieving the most contact possible between the back of the tiles and the thinset is crucial. To address the issue, guidelines from the TCNA specify that 95 percent of the back surface of each glass tile must make full contact with the thinset in order for it to be securely attached to the substrate. Over the years, seasoned manufacturers and installers each took special measures to achieve the most contact possible.

Rather than gluing mesh onto the back of the sheets, as seen with ceramic and porcelain products, manufacturers mounted the front of the tile to sheets of paper that are removed during installation. This allowed installers to utilize a technique called back-buttering, whereby they applied the grout directly to the back of a sheet of tile before adhering the tile to the concrete structure. But the installation requires more care: With paper obscuring the front of the tile, it was difficult for setters to see if the sheets were straight and properly spaced, so making adjustments was more time-consuming.

Recently, more manufacturers have begun gluing at least some of their glass products onto mesh to simplify installation. However, this reduces contact between the glass and thinset, preventing installers from meeting the 95-percent rule specified in the standard.

“If you’ve got too much glue with the mesh, the thinset will never touch the actual glass,” says Steadly. “So essentially, the thinset is bonding to the glue, not the tile. Over time, that bond is going to be weak because it’s really just the glue that’s holding it.”

To address this reality, ANSI A137.2 states that the product should be face-mounted when used in exterior or submerged environments.

Several manufacturers agree with the rule. “With a face-mounted material, the entire surface of the back of the tile is available for bonding,” says McGregor.

Quality of glass

The entry of newer manufacturers into the glass-tile market has given rise to concerns regarding product quality.

Marckx questions whether the lower-priced tiles are suitable for the demanding conditions in pools and spas. “An uninitiated buyer might consider a lesser-priced product that looks similar when pulling it off the shelf, but is it really fit for that type of use?” he says. “There’s no easy way for them to evaluate if it’s going to work for their project.”

In particular, questions have arisen about tile that originates from countries other than the U.S., Italy or Mexico, all known for producing the material. However, without empirical data that compares the glass products from different places, there is no way to ascertain whether these concerns have validity.

“I’ve seen plenty of great tile from China, Japan, Turkey and Egypt,” Fleming says. “I see glass from all over the world that is made well, and I see plenty made here that isn’t made well.”

Regardless of where the glass is manufactured, there are aspects of its production that help ensure longevity.


When forming the tile, it’s crucial that the temperature be high enough to guarantee a cohesive structure.

“You want glass that’s been fully melted and then fully refined,” Marckx says. “This means that the tiny air bubbles occurring in the volatilization and melting process are pushed out.”

The ideal temperature can vary and depends largely on the type of glass utilized and the process employed to make the tile.

“What’s most important is that whoever makes the glass tile is completely on top of their own process and that the end result is stable, stress-free and will work, with proper installation, in a pool environment,” says David Knox, founder of Lightstreams Glass Tile in Santa Clara, Calif.

If the glass doesn’t reach sufficient temperature, the various components may not completely melt and blend together, rendering the finished product less homogeneous and thereby weaker. In addition, certain types of glass can be susceptible to “cord,” or streaks with a different composition than the surrounding material that weaken the glass.

“Often when glass is not fully melted and refined, you’ll get a more brittle product, which is potentially more prone to breaking,” Marckx says.


This is the process by which glass tile cools — and it’s a key component in determining the product’s long-term durability, particularly given the temperature differentials of a pool and spa environment.

“There’s a zone, typically about a 100-degree transition point, where the glass needs to be cooled very slowly,” Marckx says. “If it’s done right, then all the stresses [are] relieved. But if the glass is cooled too quickly, there’s typically latent stress in the glass. ... It may not crack immediately, but when it’s in an installation and subject to various stresses, the glass can fracture.”

Knox points to a familiar example of this type of breakage: the lower-priced glass vases that come with floral arrangements and are prone to shattering if moved too quickly from cold to hot water or vice versa. “It might not be a well-annealed piece of glass,” he says. “So it would have an inherent stress in it. Then when subject to a direct shock, whether thermal or mechanical, the crack or stress that was sitting there, like a tectonic plate in an earthquake, goes ‘Pop.’ The stress is relieved and the vase broken.”

Improper control of the cooling procedure will result in the process occurring unevenly, with the corners of each tile cooling first because they have the greatest surface-to-air exposure. “The tile is cooling in sort of a circular fashion, and there’s more captured heat in the middle,” Marckx explains. “The outside edges will cool faster and start to contract, and there will be stress in the glass. If you even out the temperature through that critical cooling phase, then the glass gets annealed and it’s relieved of that stress.”

Timing of the process varies greatly, with some thinner glass mosaics requiring less than one hour in the annealing oven, while thicker, customized varieties could need as much as 12 hours, Marckx says.

Unfortunately, one can’t detect with the naked eye how well glass has been annealed. The cracks and stresses are too small to see without a polarized lens on a light table or the more sophisticated polariscope. When considering a glass tile, Marckx suggests that installers and consumers question the distributor or manufacturer about how the product has been annealed.


Glass tile falls into one of four categories: fused, cast, a hybrid of those two, or low-temperature coated glass. All rely, in part, on quality ingredients for a durable final product. Lower-grade materials can result in tile that is more prone to failure.

The fused approach utilizes layers of glass that are kiln-fired until they merge. This layering can produce a striking visual effect.

“I’m creating a slab of glass, cutting it into tile shapes and then refiring it,” Knox says.

Regardless of the production method, all materials should be compatible with each other, but this is particularly important for product made with the fusing process, since it involves refiring and blending together already-made glasses. If the components have varying rates of expansion and contraction, the tile will become brittle over time. “It’s very important that all the raw materials have the same coefficient of expansion and a similar viscosity that will work together,” Knox explains.

With the cast process, glass is brought to its liquid state, with color additives already in place, and poured into molds or presses that some liken to ice-cube trays. It is then gradually cooled before the individual tiles are removed. This method produces tiles of uniform appearance, with consistent color all the way through.

When purchasing tile created with the cast process, it should be noted that the raw materials can determine quality from batch to batch. The major ingredients that produce glass — silica sand, clays and fluxes — must be carefully monitored to achieve a consistent melt, and therefore consistent quality.

Uniformity also is needed for the components that supply color to the glass. Because these materials are generally expensive, some manufacturers may try to cut corners here. But doing so can result in significant changes in hue from batch to batch, so the consumer may not get what he or she expected.

To produce low-temperature coated glass tile, manufacturers take sheets of clear glass, cut it into individual tiles and add a coating on the back to produce color. The coatings should be applied at a temperature that’s warm enough to help them cure, but not hot enough to melt or fuse the glass.

In addition, some manufacturers in an effort to be environmentally friendly incorporate recycled glass into their tiles. To do this, producers purchase the recycled glass, then melt and mix it with the other components to form a whole.

But questions have begun to surface about the quality and durability of those products.

“Using recycled bottle glass may have a lot of benefits, but there are still the same, if not higher, technical standards you have to adhere to in the quality of the batching and melting,” Marckx says.

Manufacturers should take extra care to choose compatible materials with the same coeffecient of expansion.

Some industry members don’t believe this is a problem.

“There was something running around the Internet [saying] that high recycled content introduces contaminants into the glass,” Steadly says. “That’s not true. When you take any material, silica and pigment and you melt it down to a liquid state and then cool it, it’s now new glass. It’s going to hold up the same as any other glass. We’ve had all our recycled glass tested and it tests out fine.”

Marckx, who has been using recycled materials for years, believes that people leap to certain conclusions about it. “It’s probably [that] someone’s saying, ‘This product’s had a problem, and we know there was recycled glass in it.’ Therefore, they come up with their own hypothesis that it was the recycled bottle glass’s fault, when ... the melting, forming and annealing were more likely the culprits.”

Others believe that more research should be conducted. “Certainly with recycled glass, there’s the possibility of having unknown components,” says McGregor. “But I’m not prepared to say that, in general, recycled glass isn’t suited for [pool and spa] applications.”