By Bill Griese, Director of Standards Development, Tile Council of North America and Noah Chitty, Director of Technical Services, Crossville Inc.
In February, TCNA’s Bill Griese and Crossville’s Noah Chitty traveled to Castellón, Spain, to lecture to the Congress of Qualicer 2018 on research and standardization of thin gauged porcelain tiles and tile panels (GPTP) in North America. Following are highlights of their white paper on this subject, which was presented at Qualicer 2018. The paper, in its entirety with works cited, is available online at www.tileletter.com.
ANSI A 137.3 and ANSI A108.19
In 2017, the North American tile industry released two new standards: ANSI A137.3, American National Standard Specifications for Gauged Porcelain Tiles and Gauged Porcelain Tile Panels/Slabs, and its companion, ANSI A108.19, Interior Installation of Gauged Porcelain Tiles and Gauged Porcelain Tile Panels/Slabs by the Thin-Bed Method bonded with Modified Dry-Set Cement Mortar or Improved Modified Dry-Set Cement Mortar. These standards, developed for the benefit of all tile consumers, are the result of a multi-year research and consensus process of the ANSI Accredited A108 Standards Committee, which includes participants from all industry sectors.
These efforts aimed to establish a framework for specifications of products that are intentionally “gauged” to a specific thickness. Currently two classes of gauged tile products are defined by the standards:
Those for wall applications from 3.5mm to 4.9mm and
Those for floor and wall applications, from 5.0mm to 6.5mm.
Other products, which either fall outside of these ranges or for which the manufacturer has not specifically provided a gauged-thickness designation, continue to be standardized under traditional tile specifications.
Terminology and strength criteria
One of the earliest topics on which the North American industry debated was terminology. These products were called “thin” tile, but since the same technologies are also used to create thick tiles – and end-users had increasingly prioritized tile thickness as a key characteristic – a new moniker was needed. Hence, the term “gauged” was born, basing the term on one used for other construction products – such as electrical wire and sheet metal – which carry different load capabilities and usage parameters across a variety of gauges. The group agreed to further differentiate gauged products based on their size, with gauged tiles being less than a square meter and gauged tile panels/slabs being greater than or equal to one square meter.
In developing product performance criteria, the first key concern was breaking strength, as the North American requirement for traditional tiles was 250 lbf. Initially, very few – if any – thin gauged products met the requirement. Therefore, installed strength became the key to achieving performance levels comparable to those of traditional tiles whose exceedingly high breaking strength could often make up for flaws in mortar coverage or quality. With thin gauged tiles, though, the group chose to scrutinize how lower breaking strength may be offset by installation rigidity and increased mortar coverage.
Key provisions of the installation standard
To develop ANSI A108.19 Interior Installation of Gauged Porcelain Tiles and Gauged Porcelain Tile Panels/Slabs by the Thin-Bed Method bonded with Modified Dry-Set Cement Mortar or Improved Modified Dry-Set Cement Mortar, a group of installers, architects, and manufacturers conducted countless experiments to discover application and embedding techniques that make possible maximum mortar coverage, particularly for tile panels/slabs. Through these experiments, standard setting procedures for gauged porcelain tiles and tile panels/slabs were developed that facilitate optimal workmanship and system integrity.
Mortar application: It was determined that applying a layer of mortar to both the back of the panel/slab and the substrate would result in the necessary bond coat thickness of 3/16” (4.8mm) and would allow for full encapsulation of lippage control systems. Anything less than this method would result in an embedded mortar layer thickness that was insufficient to achieve the agreed-upon substrate tolerance of a maximum deviation of 1/8” in 10 horizontal feet (3mm in 3m) from the required plane when measured from the high points in the surface for floors.
Mortar properties: Mortar properties such as extended open time, flow to achieve coverage, and curing parameters appropriate to the application, as well as a requirement for suitable mortar identification through consultation with the tile and setting material manufacturer are specified in the standard.
Trowels: Only Euro-trowel, Flow-Ridge trowel, and Superior notch trowel can facilitate ridge collapse without the need to press and slide the tile. The group agreed to standardize the use of such trowels.
Embedding procedures: For floors, physically walking on the surface in the following pattern produces the greatest supporting mortar coverage:
1) walk down the centerline of the tile;
2) take small shuffling steps left and right from center to push air toward the edges.
This standardized procedure is listed in ANSI A108.19 for embedding tile panels/slabs on floors. For walls, a vibration tool and weighted beat-in paddle are specified in order to achieve optimal coverage.
For walls and floors, a vibrational tool used at the perimeter, achieved full coverage on the edge, critical for overall durability in flooring applications, and also facilitated full encapsulation of lippage control systems. For these reasons, edge coverage achieved through vibration is a provision of ANSI A108.19. The standard minimum required coverage is 80% for walls and 85% for floors. Additionally, maximum void size was established as 2 square inches (1290 square mm).
Coverage calculation: A standardized evaluation to calculate coverage was developed. ANSI A108.19 states, “In any single square foot under the embedded tile, coverage… is calculated by measuring the voids and the marked off square foot and dividing by 144 square inches (929 square cm) where the dry set mortar is not in full contact from the back of the tile to the substrate.”
Substrates: Standardized suitable substrates for the installation of gauged porcelain tiles and tile panels/slabs are mostly consistent with those of traditional tile, with the exception of direct bonding to plywood floors, which requires the use of a mortar bed or specified backer board and referencing floor rigidity requirements established by building codes and other widespread industry specifications.
Applicable to all substrates, ANSI A108.19 details required flatness as maximum deviation of 1/8” over 10’ (3mm in 3m) from the required plane when measured from the high points in the surface.
Material handling: Qualified labor and other provisions also taken into account through discussion and A108.19 standardization were adequate jobsite storage, space to maneuver panels, prevention of damage while handling and time for mortar curing. Another critical aspect of ANSI A108.19 involves usage of properly qualified installers who are equipped with proper tools and have acquired sufficient product knowledge and installation experience.
There are several other key provisions contained within ANSI A108.19, including grouting, workmanship, movement accommodation, and maintenance, completing a very comprehensive specification for how to install products defined by ANSI A137.3.
See link here for the full paper, including footnotes.