Ask the Experts – May 2018

Ask the Experts Q&As are culled from member inquiries to NTCA’s Technical Support staff. To become a member and make use of personal, targeted answers from Technical Support staff to your installation questions, contact Jim Olson at [email protected].

QUESTION

I recently installed 2” x 2” sheet-mounted mosaics in a public park bathroom. During the tile installation the general contractor provided me with limited lighting. Electricians installed LED light fixtures above and against the wall. 

During the installation, the owners of the facility were very pleased with how the product looked on the walls. But I noticed that with these very bright lights located directly over the tiles, you could see imperfections. Plus, shadows from the lighting made the tile job look like it was not done well, but when you ran your hand against the tiles you could feel that it was done properly. 

A couple of months later they contacted me for a meeting to go over the installation of the tiles because they felt it was unacceptable. When I arrived the owners went over some of the areas and claimed that I did not do a good job. I did notice some tiles that needed to be replaced, but for the most part they were installed very well. I told the owners that I do not have a problem going over quantities that needed to be replaced and that I would take care of it; we even went to another facility where a different installer installed the same type of tile but the light in that room was not directly against the wall and you could not see the cast shadows – but when you ran your hand again the wall you could feel the imperfections. The bottom line is that the owners want me to replace the whole wall, which it is not necessary to fix the problems. I also documented during the process pictures that the drywall was not properly installed and leveled, and that was another reason for the imperfections. 

Can you provide to me or help me with some sort of literature or a reference to a handbook so I can protect myself from being taken to court? Clearly this issue is because of the way the lighting fixture is located and how it casts shadows, making the installation unacceptable. I did find some information about this topic but I do not know how to approach this to avoid court. 

ANSWER

The situation that you have found yourself in is very common to our industry. We have received several technical calls about the influence of lighting on finished tile work. The design community has embraced this type of lighting to give a more dramatic lighting effect. Any type of lighting located on or near tile walls accentuates irregularities by casting shadows on the tile surface.

The good news is, our industry has addressed this issue in several places: in the TCNA Handbook, page 34; in the NTCA Reference Manual from page 121 to 127; and in the ANSI standards on page 26.

There are allowable amounts of lippage in any tile installation. There are charts in both the ANSI standards and TCNA Handbook based on the type of tile, tile size and joint width. Attached is an image of Flatness and Lippage table on page 36 from the TCNA Handbook, versions 2017 and 2018 (image courtesy TCNA).

In summary, our standards say that the angle of light cast on tile work can accentuate otherwise acceptable variance.

We have had members bring lights in to a situation like this, taking photos of the same wall under two different lighting influences. This can be dramatic and show the impact lighting has on the appearance of a installation. Attached is an image from the NTCA Reference Manual showing the same wall with two different lighting options.

As far as the surface not being flat enough to start with, there are standards for how flat a surface should be to install tile. The surface should have no deviation (hump or dip) of more than a 1/4” in a ten foot radius. As far as the substrate not being correct and affecting the installation, this should have been addressed prior to the installation. Once we start an installation we have accepted the substrate as suitable. Once we start tiling a surface
we now own it. 

Robb Roderick,
NTCA Trainer/Presenter