joint width. Attached is an image of Flatness and Lippage table on page 36 from the TCNA Handbook, ver- sions 2017 and 2018 (image courtesy TCNA). In summary, our standards say that the angle of light cast on tile work can accen- tuate otherwise acceptable variance. We have had mem- bers bring lights in to a situation like this, taking photos of the same wall under two different light- ing influences. This can be dramatic and show the impact lighting has on the appearance of a installa- tion. 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 installa- tion we have accepted the substrate as suitable. Once we start tiling a surface we now own it. – Robb Roderick, NTCA Trainer/Presenter ASK THE EXPERTS –––––––––––––––––––––––––––––––––––––––––––––––––––– Critical Lighting Interior Wall Wash Position of overhead lighting can affect perception of tile lippage. LIGHT AGAINST WALL LIGHT 24 INCHES FROM WALL 124 NTCA Reference Manual | 2017 / 2018 Chapter 6 | Specialized Installation Procedures Lighting Placement The photographs above illustrate the dramatic difference the placement of overhead lighting can make in the appearance of a tiled wall. The photographs on the left show the effect of overhead lighting panels mounted next to the wall resulting in “wall wash”. This harsh lighting technique creates harsh shadows that accentuate any irregularities in the tiled surface. The photographs on the right show the dramatic visual improvement achieved simply by moving the overhead lighting just pone ceiling panel (24”) away from the wall. The tiled wall illustrates a standard thin-set installation. The wall, fluorescent fixtures and camera angle are exactly the same in both sets of photographs. Only the placement of the lighting fixtures was changed. Glazed Wall Tile Unglazed Wall Tile The photographs on the right show the dramatic visual improvement achieved simply by moving the overhead lighting just one ceiling panel (24”) away from the wall. The tiled wall illustrates a standard thin-set installation. The wall, fluorescent fixtures and camera angle are exactly the same in both sets of photographs. Only the placement of the lighting fixtures was changed. Same wall, different lighting placement – lighting place- ment makes all the difference in perceived flaws 26 TileLetter | May 2018