Tech Talk – January 2014

TEC-sponsorInstalling ceramic tile, glass tile and stone in interior wet areas

Slope, weeps, and flashing are key to managing water and avoiding failures

Donato PBy Donato Pompo, CTC, CSI, CDT, MBA,
Ceramic Tile and Stone Consultants (CTaSC),
University of Ceramic Tile and Stone (UofCTS).  

Exterior decks and balconies, and interior showers and bathrooms have historically been problematic areas for the installation of ceramic tile, glass tile, stone tile and other stone products. Typically problems are due to installer error, such as not using appropriate materials for those applications, or not having clear enough specifications. In each case it is the result of not following industry standards. Exploration into the intricacies of exterior decks and balconies can be an entire article in itself, but for this story, we will focus on interior showers and bathrooms.

Industry standards are created by industry consensus groups consisting of installers, producers, and industry experts through organizations such as ANSI (American National Standards Institute), TCNA (Tile Council of North America), ASTM (America Society for Testing and Materials) or ICC (International Code Council).  These consensus group members combine their many years of experience with science to establish standards so problems and failures can be avoided and not repeated.  Thus if standards are not followed then known potential problems can’t be avoided.

As a forensic investigator for over 11 years, I have investigated many failed interior showers and bathrooms. I have found that the common denominators to tile and stone failures in these applications were the lack of proper slope, plugged weep holes, and inadequate flashing to contain or manage the water that resulted in various types of damages.

Managing water volume


First, consider the volume of water that showers are subjected to on a daily basis. Since these areas are likely to be subjected to more water than a typical roof is subjected to annually, it is imperative that extra care and attention are spent on specifying and constructing them. This is accomplished by properly managing the water so it is controlled and safely evacuated from those areas.

Lack of adequate slope is a common problem in interior wet horizontal applications such as shower floors, shelves and seats. It is very clear in the tile and stone industry standards, as well as in the Uniform Plumbing Code (UPC), and in the IRC (International Residential Code) or IBC (International Building Code) building codes, that the slope to drain, or away from the building, should be a minimum 2% slope. That calculates to 1/4” per foot (6 mm per 305 mm). UPC says the slope to drain in a shower must be a minimum of 1/4” per foot (6 mm per 305 mm), but not more than 1/2” per foot (13 mm per 305 mm).

Not only is it important for that slope to drain to be at the surface of the tile or stone, but it is critical that the minimum 1/4” per foot (6 mm per 305 mm) slope to drain is at the surface of the waterproof membrane or drain plane. Drains come in two sections. Where the drain clamps down on the waterproof membrane below the surface of the tile assembly, there are weep holes in the drain assembly, so that any water that migrates to the waterproof membrane can then evacuate into the drain through the weep holes.

Problem #1: Improper slope to the drain


There are  three common problems that we run into. First, the waterproof membrane is not properly sloped to the drain. In a shower this can result in the tile mortar bed staying constantly damp, which creates a musky odor in the room, or it may cause a stone or tile floor to look wet. Excessive moisture might result in the stone spalling (deteriorating) and/or staining.   Sometimes we find that the waterproof membrane is flat or even negatively sloped away from the drain, or that there are low spots on the membrane surface where water collects.

Problem #2: Plugged weep holes


The second common problem is drains with plugged weep holes.  Industry standards state that the weep holes are to be covered with pea gravel or with a plastic weep hole protector to make sure the weep holes stay open. Often this weep hole protection is left out, and mortar is placed over the weep holes, plugging them. Thus, if the waterproof membrane is properly sloped to drain, the water cannot escape into the drain. Again, this can result in the tile mortar bed staying constantly damp, which results in the musky odor in the room, a wet-looking floor or stone spalling or staining.

The term “spalling” refers to the deterioration of the surface of a stone. It is the symptom of a stone being subjected to excessive moisture over time. Spalling is typically caused by moisture migrating from the stone’s underlying substrate up through the stone to its surface where the moisture evaporates. As the moisture travels from under the stone through the cementitious materials, and through the stone itself, the moisture picks up various minerals (salts) which dissolve in the moisture. When the moisture reaches the surface of the stone it evaporates and the minerals precipitate into a solid again.  This expansion or crystallization of the mineral, referred to as efflorescence, causes the surface of stones to deteriorate to some degree.

Whether it is a shower or an exterior deck or balcony, the waterproof membrane surface must be sloped to drain or away from the building. Shower pans or receptors are supposed to have a pre-sloped mortar bed installed over the base substrate before installing the waterproof membrane. The pre-slope needs to have a minimum slope of 1/4” per foot (6 mm per 305 mm).

Problem #3: Membrane breaches3-techtalk

That brings up the third common problem that we find in showers: waterproofing or vapor retarders that are not complete or continuous. They tend to lack flashing at transition areas. Considering the potential collateral damages a defective balcony can develop, it is important to construct it like a big shower pan. Assuming that the deck has been properly pre-sloped, the waterproof membrane must continue, or be flashed, up the wall at least 3″ (76 mm) above any thresholds to prevent water from causing any potential collateral damages. All seams, penetrations and transitions must be properly waterproofed, flashed and sealed with a sealant. These are the areas that are most vulnerable to having problems, so they need to be given the extra attention to ensure they are installed correctly. The waterproof membrane should never be penetrated, unless it is unavoidable, and then the penetration has to be properly flashed and sealed with the appropriate sealants to ensure it will never leak.

Often we find that decks are sloped to their outer edge without any type of gutter or drain. The water drains over the side of the balcony and eventually results in staining along the siding, or staining and spalling the stone if there is stone siding. The latest trend is to use trench or linear drains that work very well and can be installed at the perimeters of decks or showers.


So how can a tile installer make sure that showers are given the attention they need to avoid failures? It is the same old answer.  Follow industry standards and manufacturers’ directions. It doesn’t matter who is at fault when there is a problem; everyone ends up paying – either in time to defend themselves, money to fix the problem or with their reputation. So it is in everyone’s best interest to make sure that tile and stone installations are done properly. (Editor note: please visit for the full text of this story, which also addresses exterior installations).

Ceramic Tile Consultant, Donato Pompo, CTC, CSI, CDT, MBA, is the founder of Ceramic Tile and Stone Consultants (CTaSC), and of the University of Ceramic Tile and Stone (UofCTS). Donato has over 35 years of varied experience in the ceramic tile and stone industry. CTaSC provides services in Forensic Investigations, Quality Control Services for products and installation methods to include writing specifications, training programs, testing, and on-site quality control inspection services. CTaSC is a professional consulting business comprised of accomplished ceramic tile consultants, stone consultants, ceramic tile and stone installers, architects, engineers, general contractors, construction scientists and other industry specialists and experts conveniently located throughout the US and Canada. You can reach Donato by visiting the company website at, emailing [email protected] or calling 866-669-1550.

TechTalk – December 2013

Spot-bonding to cure an uneven substrate is a no-no that even a customer can recognize

Unacceptable methods and unskilled installation set the stage for future problems

By Lesley Goddin

Sometimes the correct and incorrect ways to install tile are so clear and intuitive that even a non-tile- professional, new homeowner, realizes something is amiss, even if “reputable” builders or less-informed tile installers do not.

Such is the case of a soon-to-be- homeowner, Sean Hobbs of Oviedo, Fla., and his wife Kimberly, who elected to inform themselves about materials and installation techniques as their home was being built. Some techniques seemed questionable, and Hobbs contacted NTCA for guidance in the matter.

“It seems that the voids left by the patty technique would be undesirable and potentially weak areas should they get knocked,” the homeowner astutely observed.

“It seems that the voids left by the patty technique would be undesirable and potentially weak areas should they get knocked,” the homeowner astutely observed.

Hobbs wrote, “The tile on the vertical walls of the showers are being applied using a ‘patty’ technique. We wouldn’t have been aware of this except that the water proofi ng Hydro Guard 1 was left unfi nished on one of the showers and the tilers needed to remove the tile to correct this. Not a single one broke. Mike Holmes of Holmes on Holmes and Holmes Makes it Right on HGTV described tile coming off easily and without breaking as a sign of poor work, so from this I felt the work wasn’t being
done well.

“It seems that the voids left by the patty technique would be undesirable and potentially weak areas should they get knocked,” Hobbs astutely observed. “I thought the only technique was to apply the thinset to the walls, use the notched trowel to comb the thinset, place the tiles, and try to get as close to total surface contact with the back of the tile. Some even recommend taking off every fifth tile to confirm this by inspecting the back. Others recommend a very thin ‘back buttering’ of the tiles to be sure of this total contact.”

Hobbs is speaking the language of the skilled tile installer here! He scoured the internet for proper tech- niques, which he shared – to no avail – with his builder. He revealed, “My wife and I were told by the builder that the directions on the bag of thinset were merely ‘recommendations.’”

The builder insisted that he is following best practices and lets “’building science’ guide his build- ing materials and their installation,” Hobbs said. “As it stands now, he is accepting the tiler’s reasoning that the DUROCK® and PermaBase® walls – which the same tilers themselves installed just a few weeks ago – are a bit off and they need to use this patty technique to perfect the tile so that the look is right.” The builder main- tained that using the aforementioned proper method would not allow the installers to fine-tune their placement to achieve a good look due to the “suction” of the tiles.

Shoddy work on display

Hobbs observed that “such a small amount of thin-set patties were utilized, that tape and even screws (piercing the waterproof membrane) were used to hold the tiles up and prevent them from sliding."

Hobbs observed that “such a small amount of thin-set patties were utilized, that tape and even screws (piercing the waterproof membrane) were used to hold the tiles up and prevent them from sliding.”

Hobbs observed that “such a small amount of thin-set patties were utilized, that tape and even screws (piercing the waterproof membrane) were used to hold the tiles up and prevent them from sliding. It is my opinion that one of the reasons the builder allowed this inferior work to be performed was to get the home ‘Parade Home-ready’ since our home – with the builder’s sign prominently displayed – was to be featured for a local annual public display of new and renovated homes.”

Hobbs sought recommendations from TCNA and received information from industry consultant Dave Gobis which included ANSI tile setting standards, and two articles – one of which, “Dots, Spots, Dollops and Whatever,” appeared in the April 2013 TileLetter.

The builder’s solution to the voids under the wall tile was to pour a slurry behind the installed tiles to fill in the spaces.

The builder’s solution to the voids under the wall tile was to pour a slurry behind the installed tiles to fill in the spaces.

“While the patty work continued, the builder was searching around to find some other ‘expert’ to refute Mr. Gobis’ perspective because the builder was sure it was simply a different technique,” Hobbs added. “Most of the remediation (certainly not my first choice) was to grout all but the top tiles, remove the top tiles, pour a slurry to fill the voids while gently tapping with a rubber mallet to help the slurry settle, and call it done.

“The builder states that he has filed paperwork with his insurance company just in case there are any future problems with this tile install for our home,” Hobbs said.

In addition to the wall tile fiasco, Hobbs specified and paid extra for Ditra uncoupling membrane he’d seen recommended by Mike Holmes. Floors in his former home had cracking tiles and he wanted to eliminate this in the new place.

“What we found by dragging a long thin metal rod lightly across our floors is that there are numerous and large areas of tile floor with 12”x12”, 12”x24” and 24”x24” in a Versailles pattern that are hollow underneath,” Hobbs said. “Our builder’s response when shown and allowed to hear this was ‘it’s hard to lay tile and get it just right.’ We have ongoing issues after moving in June of 2013.”

Bringing his concerns to the NTCA, he asked, “Am I being overly concerned here? Are these appropriate issues to bring up? Should I consult a local tile professional, possibly one in good standing with the National Tile Contractors Association organization, to get a second opinion?”

NTCA responds!

Well, dear reader, I can imagine that you are thinking, “You SHOULD be concerned, Sean!” and “Good eye!” Here’s how Gerald Sloan, NTCA presenter and technical con- sultant, responded:

“I highly recommend choosing a tile contractor that is a member of the National Tile Contractors Association,” Sloan said. “Please visit our website, then go to member locator to find a member contractor close to you.

“As a member, the tile contractor is privy to yearly updates on industry- recognized installation standards and cautions, in addition to product limitations,” Sloan said. “Another great member benefi t is technical sup- port that comes from our Technical
Committee where issues that concern tile contractors are discussed with efforts to avoid actions that have caused tile installation-related failures. A member who is active in our association is well-armed to avoid potential failures due to inappropriate installation practices. We wish all tile contractors would be a part of the NTCA, so we could eliminate all installation related failures.”

Sloan addressed the folly of incorrect spot bonding especially to correct uneven substrate conditions.

“As for your question related to spot bonding the tile to correct out- of-plane or out-of-plumb wall substrate conditions, this is high risk for a failure due to several factors,” Sloan said. “One is, as you men- tioned, impact loads. Those areas behind the tile that do not have coverage are much more likely to break if an impact condition should occur.

“Another potential problem is in a wet environment such as a shower; open pockets can harbor dampness much longer, and the body oils and dirt from your body can penetrate through the tile and grout joint – even if it has a quality sealer on it,” Sloan said. “Over time, this mate- rial may accumulate and become food for B.O.G (biological organic growth) or mold.

“The other reason we should not spot bond with common multipurpose thin-set setting materials is because they have a high rate of failure due to product shrinkage,” Sloan added. “The multipurpose thin-set products we work with most often are not designed to be built up to more than 1/4” thickness as measured after the tile has been installed – remember it’s called thinset. If it exceeds maximum allowable finished thickness, it has been proven to fail due to shrinking as it cures.”

The Tile Council of North America Handbook for Ceramic, Glass and Stone Tile Installation has a generic caution given in the note section (p. 17 in the 2013 edition) about not using medium bed mortars to true-up underlying substrates, Sloan said. Additional recommendations for mortar use are listed on page 35 of the Handbook.

The ANSI Standards, on page 88, in section in the Definitions of Latex-Portland Cement Mortar, state: “Modified dry-set mortars are designed as direct bond adhesives and are not intended to be used in truing or leveling underlying substrates or the work of others.”

The homeowner said, “My wife and I were told by the builder that the direc- tions on the bag of thinset were merely ‘recommendations.’”

The homeowner said, “My wife and I were told by the builder that the direc- tions on the bag of thinset were merely ‘recommendations.’”

Bart Bettiga, NTCA executive director, jumped in on the discussion. “We don’t specifically have a section that addresses spot-bonding or pattycaking because, until recently, we were not aware that this practice was gaining steam,” he said. “We intend to alert our ANSI and Handbook committees that we may need to go even further to address this.

“There is a reason why patching and leveling products are made; because they are designed for these purposes,” Bettiga added. “The mortars that are manufactured to be used to direct-bond tile and stone are formulated to be spread to a certain thickness. When you deviate from this intention, you defeat the intended purpose of the products. We are not aware of any thin-set manufacturer that would recommend or warranty their products to be used in this fashion.”

Instead of using mortar to even up the substrate, Sloan said, “If the framing is out of plumb, framing should be corrected by shimming, sistering, scabbing, or total removal and replacement. Do not true up with thinset because the thicker places shrink more than the thinner places, thereby creating stresses that often cause the loss of bond to the tiles in random areas. The American National Standard Institute has a thin-set coverage requirement under A-108 which mandates wet area tile installation thin-set setting coverage to be 95% – 80% coverage for dry areas – with all edges and corners covered.”

Spot-bonded tiles came off the wall easily and intact - evidence of badly-bonded tiles.

Spot-bonded tiles came off the wall easily and intact – evidence of badly-bonded tiles.

This game of “patty-cake” played by the builder is setting the ground- work for future problems, ones that he has opted to cover by insuring the work instead of doing it right from the beginning.

Tech Talk – November 2013

TEC-sponsorKeys to successful installation of large thin tile panels

tom_plaskota_webBy Tom Plaskota, Technical Support manager, H.B. Fuller Construction Products

Large-format tile has become a popular choice for commercial floor and wall installations. Because it requires fewer grout lines, large-format tile visually expands rooms and produces a neater, modern appearance. Building owners and designers, now more than ever, are demanding these aesthetic benefits. Meanwhile, technological advances have enabled manufacturers to produce larger – and thinner – porcelain tiles, some with facial dimensions as large as 5’ (1.5 m) x 10’ (3 m). Thicknesses are reduced compared to traditional tile, ranging from 1/8” (3 mm) to 9/32” (7 mm).

These larger and thinner tiles can be challenging to handle and install. Here are some key factors to consider:

Handling – Large-format tiles often arrive in oversized crates, which require specific handling equipment. To prevent damage during forklift operation, specific fork sizes must be used. For example, to handle a crate of 3’ x 10’ tiles from the side, 44” long forks are recommended. To handle the same crate from the narrow end requires forks that are at least 84” long. Lifting multiple crates with longer forks may require forklifts with a greater lift capacity.

fig1_tectalkTools and equipment – Specialized tools and equipment are currently available for the installation of large porcelain panels. Innovative trowels with unique notch configurations can help increase the consistency of the mortar coverage on the back of the tile (See fig. 1). As with any size tile installation, full and complete coverage provides a strong bond and minimizes the likelihood of damage from impact or heavy loads.

Fig2-tectalkTo assist in the handling and setting of individual tiles, frames and handles with suction cups can be purchased or rented from tile distributors. Since mis-cuts of large panels can result in costly waste, the use of a rail cutting system is highly recommended (See fig. 2).

Installation materials – Since not all setting materials are appropriate for installing large porcelain panels, setting-material manufacturers have specific large-tile product recommendations. Whether you are installing 1/8” (3 mm) thick tiles that have a resin/mesh backing (See fig. 3) or 7/32” (5.6 mm) tiles with a porcelain bonding surface, the greater bond strength and resistance to impact of latex/polymer modified portland cement mortars are required. The “tack time” of a mortar is another consideration. When troweling mortar onto a substrate, it is important that the mortar surface remains in a wet, tacky state and doesn’t skin over before the tile is set. Tack time is especially important when troweling out the area to set a 30-plus square foot tile.


Setting-material manufacturers must also evaluate grout requirements for reduced thickness porcelain panels. Strong durable grouts are required for these installations for two reasons:

1. Grout-joint depth is limited by the reduced thickness of the tile

2. Reduced-thickness tiles have a rectified corner edge, which may be susceptible to impact damage in some circumstances. Grouts with premium strength qualities address these conditions.

Substrate preparation – First, check with the tile manufacturer to make sure your substrate type is acceptable. For example, some large thin-tile manufacturers limit floor installations to concrete substrates. While a clean, sound substrate is critical to any tile installation, large porcelain panels have the added criteria of substrate flatness. The maximum allowable variation in the substrate for tiles with all edges shorter than 15” is 1/4” in a 10’ span. There should be no more than 1/16” variation in a 10’ span when measured from the high points on the surface. For tiles with at least one edge 15” in length, the maximum variations are 1/8” in 10’ and 1/16” in 24”. For floor installations, a self-leveling underlayment can help meet these substrate requirements.

Staffing the job properly – Having the right size crew is critical. The largest of these tiles must be handled by at least two people. Back-buttering is typically required, with the mortar being applied to the substrate and the back of the tile by two people simultaneously. To keep pace with the installation, at least one individual will be required to mix and maintain the flow of mortar. Taking this into consideration, even the smallest installations require at least a four-person crew.

Finally, there are additional recommendations that manufacturers can provide, so the best approach is to consult your tile and setting material manufacturer before you begin the installation. That way, you’ll be better prepared for the challenges you may face and have the knowledge to take on large tile installations with confidence.

The TEC® brand is offered by H.B. Fuller Construction Products Inc. – a leading provider of technologically advanced construction materials and solutions to the commercial, industrial and residential construction industry. Headquartered in Aurora, Illinois, the company’s recognized and trusted brands – TEC®, CHAPCO®, Grout Boost®, Foster®, AIM™ and others – are available through an extensive network of distributors and dealers, as well as home improvement retailers. For more information, visit 

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