Reconciling promise and reality with thin porcelain tiling

by Catherine Howlett | May 1, 2013 11:16 am

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by Neil McMurdie, PhD
In 2009, amid great fanfare and drama, the latest innovation in porcelain tile technology was formally announced and touted at the Cersaie exposition in Bologna, Italy. Multiple manufacturers had developed and launched new commercial tile lines that were bigger in size and thinner than anything else currently on the market.

The halls of the exposition buzzed with the news of tiles as thin as 3 to 5 mm (0.12 to 0.2 in.) in various sizes and patterns with the potential to revolutionize the industry. The new technology was expected by some in the industry to bring tiling back into a leading position as a ‘green’ wall and floor finish. Thin tiles weighed less per square foot, could be produced and shipped with a lower net carbon footprint, and produced with the consumption of fewer natural resources. Suddenly, thin was in.

Prior to the formal announcements at Cersaie (and all the press releases that followed), work carried out in the preceding two or three years had shed some light on the thin tiles. Fiberglass mesh had been applied to the back of some of the thinnest products to give strength using state-of-the-art adhesives that would work with standard cement adhesives. Expert installers were already working to find ways to direct bond these tiles in vertical positions on walls and exterior façades.

The biggest opportunity for total square footage of application would eventually be if the materials could be applied to flooring systems not only in new construction, but also, more importantly, in renovations. A thin tile would reduce added dead-load weight and make renovations easier with less need to adjust floor heights and make doorway transitions. The question that immediately came up was how to install and what adhesives should be used on the new thin tiles to make the launch a commercial success.

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Nothing like hitting a moving target
Since the 2009 announcement, engineers and developers at major tile manufacturers around the globe have continued to make progress in the way thin tiles are manufactured and fabricated. As of late 2012, at least three technologies are used.

Most of the 5-mm thick tiles are produced using a variation of the traditional pressed methods. Here, large presses compact the starting ceramic powder in a mold in a sequential process. Newer processes use a continuous press on a conveyer belt to make long sheets of tile with a wide variety of patterns and layers. The continuous sheets are then cut to size for shipment. The available maximum size has grown from around 1.2 m (4 ft) in 2009 to tiles 1 x 3 m (3.3 x 9.8 ft) long today—not the kind of flooring the average DIYer throws in the back of a minivan for a quick weekend project.

More companies and countries have jumped on the thin-tile bandwagon; the market has become global in the past two years, with each new product containing its own variations and nuances. The net effect has been to make it just that much harder for the architect, design professional, contractor, and installer to know exactly what is best and where to use the readily available new products.

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At this point, there are no international (or even national) standards guaranteeing the performance of thin tiles. There is an effort by the Tile Council of North America (TCNA), working with the International Organization for Standardization (ISO), to produce a standard similar to ISO 13006, Ceramic Tiles–Definitions, Classification, Characteristics and Marking, as quickly as possible. However, it will still be a few years before this would be published. In the meantime, guidance is needed regarding the three biggest tile-installation questions plaguing the industry:

This author’s company embarked on a research strategy that first focused on finding the best ways to actually install tiles using floor installations as the model. At the same time, work was conducted to look at the best-suited setting materials to better promise success in the real world, where floors would be subjected daily to thermal and mechanical forces. Once the installation materials and methods were standardized, it was possible to look at how the tiles themselves would hold up under load, again using floor installations as the model.

The right tools and methods for the job
As part of the effort to develop consistent methods to install thin tiles with high mortar coverage to support the installations, a wide variety of trowel types were tested. Out of many, two emerged as the best in class for these installations.

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Shown in Figure 1, these trowels gave the highest percentage of coverage for the tiles. As part of the installation strategy, the tiles were always back-buttered using the same trowel; the mortar lines on the floor and tile were aligned parallel for maximum air release and coverage. Researchers found a small, hand-held orbital sander, for vibrating the tile into place, maximized the result and minimized stress on the installer (Figure 2).

For every installation, both horizontal and vertical, the best results were obtained when the substrate was properly prepared (i.e. very flat) and a tile-leveling system was used. Flatness of the floor or wall must meet TCNA Handbook guidelines for substrate flatness: a maximum of 3.2 mm (1/8 in.) deviation in 3.1 m (10 ft) as measured by a straight edge for any tile that has any one dimension longer than 381 mm (15 in.). Specifying that the tile contractor and/or GC plan for the needed substrate preparation in the bidding process was found to be a key to a successful, cost effective installation.

The advantages of leveling systems in reducing lippage during installation and making the final appearance acceptable to the customer were also found to be too huge to ignore. Many tile-leveling systems are now commercially available and provide choices to the installer that can best accommodate their workflow and specific installation practices.

The largest tiles also require special racks and frames that support the whole tile and allow a two-person installation crew to manage its installation (Figure 3). The racks are available through tile-distributors, and should be considered if very-large-format installations are planned.

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Determining the proper mortar
During the development work, various mortar products were evaluated as part of the screening process to find the best recommendations to share with the market. The harsh conditions experienced by both floor and exterior vertical installations were used as guidelines for the stresses that must be survived in successful real-world installations.

Using both practical tests, as well as sophisticated computer simulations, researchers determined the mortars best-suited for the installation of thin tiles should be high in quality with a level of performance commensurate with at least C2S1 (i.e. improved-adhesion, deformable cement mortar) under ISO 13007-1, Ceramic Tiles–Grouts and Adhesives Part 1: Terms, Definitions, and Specifications for Adhesives. Mortars with the ISO 13007-1 Thixotropic (T) rating were also found to be useful. For extreme conditions with exterior thermal exposure or freeze thaw conditions, an ISO 13007 C2S2 (i.e. improved adhesion, highly deformable cement mortar) product is even better for thin tile installation.

The test procedures used in ISO 13007 were developed over the past 15 years and include the most comprehensive set of tests in the world for measuring the overall strength of a mortar under real-world conditions. Under the ISO 13007-1 system, a cement-based mortar is able to achieve a C2 (improved adhesion) classification only if it is able to maintain a tensile pull strength greater than 1 N/mm² (145 psi) under room temperature, freeze thaw, water immersion, and 70-C (158-F) heat age. The deformability to give the S1 rating uses a specially designed slab of the mortar and measures its deflection before breaking to predict the flexibility. An S1 has to be able to bend 2.5 mm (0.1 in.) under the test conditions; an S2-rated mortar can bend at least 5 mm (0.2 in.) under the same conditions. Higher deformability requires a higher polymer content in the mix to adapt to the flexibility and adhesion requirements for the application.

Time to torture the tiles
Once the installation methods and materials had been worked out and optimized, the next step was to test the total installation. Without an existing set of international and/or national standards for thin tiles, a more creative solution was needed to stringently test the performance of the tiles themselves under known conditions.

A Universal Flooring Tester was employed to perform ASTM C627, Standard Test Method for Evaluating Ceramic Floor Tile Installation Systems Using the Robinson-type Floor Tester. This simulates, in a reproducible way, the strains on a floor equal to a residential home environment all the way up to the most strenuous commercial applications. The stresses range from high heels to rolling loads, forklifts, and commercial equipment.

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ASTM C627 was developed using a series of wheels of different hardness to assess the installed flooring system’s ability to withstand the real-world stresses found in residential and commercial installations. TCNA has assigned tile service ratings based upon the number of cycles successfully completed. To be given a particular rating, the flooring system being tested must not fail during the given cycle. The first time failure is noted, the test ends and the previous cycle’s rating is applied (Figure 4).

Using this test method (among several others), various thin tiles from many manufacturers were tested for adhesion, water resistance, and resistance to compressive loads. During the testing, the use of the leveling systems was confirmed as a best practice. It was also found there was a reproducible pattern to the failures observed with thin tiles. The testing of the thicker 4.5 to 6-mm (0.18 to 0.24-in.) tiles showed the most reproducible. With the proper tile, results up to ‘heavy commercial’ were reproducibly obtained. The result was shown to be tile-specific, so the thin-tile manufacturer must be party to any decision about its product’s performance rating. The techniques developed for floors also work for walls and exterior installations by analogy, since the coverage requirements are the same.

Looking toward the future
Tile manufacturers continue to work to improve their processes and make thin tiles stronger and better, and mortar and installation techniques are continually being developed and refined. There is a real opportunity for the industry to capitalize on all the advantages initially discussed at Cersaie in 2009. The cutting edge—the thin tile edge—is catching on, creating new opportunities for both designers and product manufacturers to bring lasting, sustainable beauty to the marketplace.

Neil McMurdie, PhD, oversees the development of new technologies and products for MAPEI Americas. He has 17 years of experience in chemical research, and is a member of the American Chemical Society (ACS), the Materials and Methods Standards Association (MMSA), the American Concrete Institute (ACI), the Adhesives & Sealants Council (ASC), and the Ceramic Tile Distributors Association (CTDA). McMurdie received the U.S. Environmental Protection Agency (EPA) Presidential Green Chemistry Challenge Award in 2001, and he is a holder of nine U.S. patents. He can be reached at nmcmurdie@mapei.com[7].

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