ASK THE EXPERTS QUESTION I have a school cafeteria with marble thresholds, all of which are broken. Is there something more stable that I can use to replace them? There are sev- eral: 3’, 4’ and up to 8’ lengths. Thanks. ANSWER While marble is among the softer natural stones, if the sub- strate is sound with no deflec- tion and if the marble is prop- erly bedded, it should hold up well. As an alternative, I would sug- gest contacting a stone fabri- cation shop. They often have remnant pieces of harder stone, Corian® , or composite materials that they can mill to your speci- fications for length and width. They can also put beveled or bullnose edges on them for you. I have found that 2cm thick material works well for this sort of thing. TCNA Handbook Method TR611-16 is your reference for more information and a sche- matic detail for proper installa- tion of a threshold. Any material you install will still require proper preparation of the substrate and proper bed- ding with appropriate mortar. – Mark Heinlein - CTI #1112 NTCA Technical Trainer/ Presenter QUESTION Any chance you’ve seen discoloration on grout that’s brownish red? I have a few the- Sponsored by 20 TileLetter | March 2017