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Critical Lighting Effects on Tile Installations

GENERAL : This section is to make the tile contractor aware of adverse conditions on jobs that can be affected by significant amounts of natural light and/or those that use wall wash, graze or similar type lighting.

CAUSES

CORRECTIONS

• When natural or artificial light shines on walls and floors at an angle almost parallel to tile surfaces, normal and acceptable inconsistencies in the tile work are highlighted by shadows that exaggerate these conditions and can magnify the effect of natural variation in materials. • Use of wall wash, graze or cove type lighting, where the lights are located either at the wall/ceiling interface or mounted directly on the wall, may produce shadows and undesirable effects with ceramic tiles. • Small die release lines inherent on the edges of some ceramic and mosaic tiles, rarely noticeable when installed under normal lighting conditions, can produce large shadows from wall wash lighting.

• Substrate should comply with the flatness requirements in ANSI A108.02-4.2. It should be noticed that the effect from irregularities in the substrate increase as the tile size increases. As a result, substrate requirements become more important as tile size increases. • Flatness requirements need to meet ANSI A108.01-2.2 or correction of the substrate the specification should include language to provide a separate bid allowance for any necessary floor or wall preparation needed to bring the floor or wall into tolerance. • Lippage is most significantly influenced by substrate flatness and the tile’s facial dimension irregularities. The information contained in the “Lippage guidelines, explanation and caution” section of ANSI A108.02-4.4 should be heeded and used to explain how the tile installation will be effected. • To minimize lippage due to tile’s facial dimension irregulari ties , specify tile that meets the dimensional requirements for rectified tile according to ANSI A137.1 and use a larger grout joint. • Some patterns, such as 50% offset (1/2 offset or brick-joint) pattern, accentuate the effects of warpage and result in more lippage. • Designers should consult with the tile manufacturer to discuss grout joint size and pattern selections that will minimize issues relating to flatness and lippage (25% [1/4] or 33% [1/3] offset patterns). • Wider grout joints allows for more gradual changes to minimize lippage due to warpage. • Provide a mockup with actual lighting. See ANSI A108.02-2.2.

• Direct bond installations over walls that have not been properly prepared can increase shadowing effects.

• Fixture walls can be accentuated by wall wash lighting due to installations/preparations by other trades.

• Surface trim/accent features not matching wall tile unit create misaligned grout joints and thickness of tile that produce irreg ular shadows.

• Scored/cut tile grout line will produce different shadows on the factory joint and the installed joint, amplified by critical lighting

• Allowable/excessive lippage and warpage can be accentuated by critical lighting.

NOTE: Lippage is a condition where one edge of a tile is higher than an edge of an adjacent tile, giving the finished surface a lipped or uneven appearance. This condition is inherent in all installation methods and may also be un avoidable due in part to the way tile is manufactured. Please consult ANSI A137.1 for more information.

• Cushioned or beveled edge tiles can minimize the effects of lippage.

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NTCA Reference Manual | 2024 / 2025

Chapter 9 | Specialized Installation Procedures