zellige specification guide

 

clé is honored to share one of our all time favorite materials that has graced the tile community since at least the 14th century. zellige is a tile that has retained its ancient and archaic tile making process and, therefore, has all the primitive qualities that have become synonymous with the monicker - zellige. essentially, a glazed terracotta tile; hand hewn, olive-pit fired and hand chiseled to-size, zellige are a testament of ancient tile craft. we like to refer to them as the prima materia of the tile world. If your order doesn’t contain tiles with pits, cracks, shade/size variations and chipped edges - it’s NOT zellige. 

 

 

general description

zellige is a series of glazed terracotta tile, handmade in morocco. It is a low-fired terracotta that is used throughout morocco for all applications- floor and wall, interior and exterior, and water treatments ( pools and fountains ). available in a variety of sizes, and colors, zellige is a prestigious architectural finish for the finest projects. they may be installed using most industry accepted processes, typical for standard ceramic installation on a variety of substrates. clé provides an installation guide for specific installation requirements. 

 

nominal sizes

 

  • 4x4 tiles (4”x 4”x 3/8”)
  • 2x2 mounted (2”x 2”x 3/8”)
  • 2x6 bejmat (2”x 5.5” x ¾”)
  • 3.5 hex (3.5” x 3.5” x 3/8”)

  

available trim

trim is not a typical part of the zellige tradition. trim, in general, is not a tradition of tiles outside of the U.S. and specifically for tiles that have an ancient history. for jobs requiring a finished edge - we recommend the traditional craft of trimming tiles- 

  1. for turning corners and for mud-set tiles, we recommend mitering your tiles. this provides a beautiful corner finish and in the case of a mud-set requiring a quarter round - this substitutes the quarter round finish with a squared miter finish. 
  2. for finishing edges on a vertical surface, we recommend building up your sheetrock surface to allow the plane of the zellige to be on the same plane as your sheet-rocked wall. for a less preferred ( and non-traditional ) edge-trim you may also elect to use schluter style edge-trim. ( see schluter.com for trim options )

 

 

standard specifications

zellige tile shall be selected by the architect/designer/owner from clé zellige standard sizes, shapes and glazes; and shall meet the requirements of ANSI 137.1 as special purpose tile; ASTM C1088-12, grade exterior, type tbx, for physical properties; and ASTM 1405-12 class exterior for properties of finish. most units will meet pci specifications, but need to be requested as such if required.

note: interior/exterior specification. ok for wet applications ( pools & fountains ) but NOT Ok for freeze/thaw.

all glazes will contain a random quantity of pits, cracks, crazing and edge-chipping and therefore will not meet the crazing requirements of ASTM 1405-12. 

COF specifications

 

  

COMMERCIAL

 

  • zellige is a glazed tile with a COF rating of approximately .25 to .30. COF requirements are .60 or higher. however, zellige sized 2"x2" and smaller provides enough COF rating due to the grout joints. 
  • zellige that is unglazed has a COF of approximately .80, which is suitable for COF requirements in wet areas. 

 

  1. absent an exception below indicating otherwise, glazed tiles should not be used in floor applications where there is a consistent surface presence of water, oil, or grease. this includes outdoor areas.

 

  1. proper maintenance is critical. Improper maintenance and improper maintenance products can result in a build-up on the surface of the tile causing the tile to be slippery. see maintenance recommendations.

 

  1. professional restauranteurs use special floor cleaning machines and cleaners to assure removal of contaminants, which are critical to maintain slip resistance in dining areas. restaurant and commercial kitchen applications are considered high-risk areas subject to floor contamination by substances that increase slipping. clé does not recommend the use of glazed tile in a commercial kitchen unless the COF exceeds .80 wet. the use of a glazed floor tile in a dining room of a restaurant is subject to the same risk factors. a glazed floor tile or porcelain tile may be suitable for the dining area if: (a) the COF meets or exceeds .60 wet, AND (b) the utmost care is taken to properly clean the floor and minimize the presence of water.

 

  1. pool decking has a continuous exposure to standing water and clé does not recommend glazed tile on pool decks unless the surface (a) has minimal glaze, (b) meets or exceeds .60 COF wet, (c) has a textured surface, is unglazed or 2"x2" or less in size and (d) is not polished or semi-polished. proper drainage is a necessary pre-requisite for all pool decking tile applications.

 

  1. exterior applications, excluding pool deckings, are considered to have a continuous exposure to standing water due to weather conditions. glazed and unglazed ceramic and porcelain tiles are not recommended for exterior floor applications unless the tile surface: (a) meets or exceeds 0.60 COF, (b) has a textured surface, is unglazed or 2”x2” or less in size and (c) is not polished or semi-polished. 

NOTE: Exterior areas require extra attention to minimize slippery conditions including proper drainage, systematic clean up of wet or contaminated conditions, and regular inspection of tiled floor surface to assure immediate correction of wet or contaminated conditions.

 

  1. slippery conditions can be minimized by (a) limiting foot traffic in wet conditions, (b) prompt removal of contaminants, (c) effective drainage, and (d) proper maintenance.

 

  1. polished and semi polished surfaces create a very smooth surface. clé does not recommend polished surfaces ( unless 2”x2” or smaller ) in any areas subject to water, oil, or grease exposures.

 

 

COF specifications ( commerical ) continued 

 

  1. ramped surfaces, irrespective of the degree of incline, requires a more slip resistant surface for safety purposes. clé recommends a minimum of .80 COF on all ramps or inclined flooring.

 

  1. test methods - there are many different test methods for slip resistance. the tile industry uses ASTM C1028. clé recommends that customers have tile independently tested to determine if the clé product meets the requirements of the customer's preferred test method (if other than ASTM C1028) prior to product selection. be sure to test competitor's products under any preferred alternative method for comparison purposes. clé does not warrant that any of its products will meet any testing parameter other than that measured by ASTM C1028.

 

  1. No floor tile is "slip proof."

 

 

RESIDENTIAL

 

  • zellige is a glazed tile with a COF rating of approximately .25 to .30. COF requirements are .60 or higher. however, zellige sized 2”x2” provides enough COF rating due to the grout joints. 
  • zellige that is unglazed has a COF of approximately .80, which is suitable for COF requirements in wet areas. 

 

  1. glazed tiles should not be used where there is a consistent presence of water, oil, or grease unless COF exceeds 0.60.

 

  1. proper maintenance is critical. Improper maintenance and improper maintenance products can result in a contaminant build-up on the surface of the tile causing the tile to be slippery.

 

  1. exterior applications, including pool deckings, are considered to have a continuous exposure to standing water creating a potential for a slippery floor surface. clé does not recommend glazed tiles on exterior applications unless the tile surface is: (a) sufficiently protected from direct weather elements, (b) equal to or greater than .60 COF wet, (c) textured, unglazed or 2”x2” or less in size (d) not polished or semi-polished.

 

  1. ramped surfaces, irrespective of the slant of the incline, require a more slip resistant surface and clé recommends a minimum of .80 COF on these surfaces.

 

  1. "polished surfaces" create a very smooth surface. clé does not recommend polished surfaces in any areas subject to water, oil, or grease exposure.

 

  1. no floor tile is "slip proof."

 

availability

most zellige is provided in a limited stock availability. when stock becomes sold-out, for purposes of specification and depending on volume production fluctuations and shipping limitations, a lead time of 8 - 10 weeks is sufficient in most cases. check with clé for verification of delivery.

 

custom availability

clé offers zellige in customized glazes, shapes and sizes. time frames and costs TBD based on request. 

 

color variation

zellige glaze colors vary from tile to tile, some more than others. these variations are intentional, resulting from our commitment to the use of ancient glaze production methods and use of raw materials. when specifying zellige, if color consideration is paramount, always work from a sampling of 3 or more tiles, which represent the range of color you can expect on the job. unglazed zellige - referred to as the color “natural”– will require the same sealant methods as our standard unglazed tile sealing.

crazing

crazing refers to the hairline cracks which may occur in the glaze surface of zellige after firing and is common in hand crafted tile. to minimize the possibility of staining clé recommends using a penetrating sealer or grout release. If sealer or release is required, please test a small section following the sealer/release manufacturer’s instructions.

 

size variation

all zellige are hand chiseled to size. this creates obvious size variation which is part of the zellige effect. please anticipate size variation in width and length, based on this chiseling. due to shrinkage from wet to fired clay in the firing process, our tiles are subject to size variation in depth, as well. the thickness is 3/8" ( for all sizes except 2"x5.5". that thickness is 3/4")and can vary, along with other specified dimensions.

 

pitting, cracking & edge-chipping

again, based on the archaic methods of the mining and firing of the terracotta zellige clay body and the impurities found in the raw materials used for the glazes, your order of zellige will contain tiles that are pitted through the glazes to the clay body, as well as have a percentage of about 20%-30% that will contain cracks, crazing and edge-chipping. should your project not want as many tiles containing these imperfections - we recommend ordering at least 20%-30% more tiles, to allow your contractor to cherry-pick these imperfections from your order. 

note - clé does not suggest this recommendation as a preferred form of zellige installation, as it falls outside a standard zellige finish and will not yield your project the traditional zellige surface for which they are known.

 

installation

installation methods should conform to the tile council of america “handbook for ceramic tile installation” (current edition). DO NOT install from unblended boxes. zellige from several different cartons should be mixed to achieve the best overall blend of color and surface imperfections. other systems are available and the manufacturer’s recommendations should be followed.

 

grouting

It is recommended that zellige not use a grout joint ( should be butt jointed ). based on size variations, wedge spacers can be used to allow for variation in the butted tiles. 

NOTE: grout is customarily used to fill in the pits, chips and cracked portions of the zellige. once grouted space, all the grout should be sealed after installation.

 

maintenance

minimal maintenance is required. mild soaps should be sufficient for most cleaning. test any cleaners before general use.

 

durability considerations

depending on specific site conditions, zellige are subject to wear over time. this inherent traffic pattern is, again, a highlight of using zellige and should be both anticipated and favored. to minimize sizeable traffic damage, a means for people to clean abrasive materials off their shoes before walking on a glazed zellige floor should be provided.

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