The primary focus of tile installers is to set tile on a substrate the meets tile industry standards, but many times these conditions are not provided. These site conditions place the tile installer in a tough spot and an even tougher decision; accept it as is or say no.
The American National Standards Institute (ANSI) specifications provide several industry standards that are there to help the installer obtain good site conditions. ANSI A108.02 states the following:
4.1 Inspection of surfaces and conditions: Prior to commencing ceramic tilework, the tile contractor shall inspect surface to receive tile and accessories, and shall notify the architect, general contractor, or other designated authority in writing of any visually obvious defects or conditions that will prevent a satisfactory tile installation. Installation work shall not proceed until satisfactory conditions are provided.
4.1.1 All surfaces shall be structurally sound, clean dry, and free of oily or waxy films and all foreign matter. Concrete surfaces shall be free of form oil, curing compound, laitance, and cracks.
4.1.4.3.1 Sub-floor surfaces: For tiles with all edges shorter than 15 in. (0.38m), the maximum allowable variation is no more than 1/4 in. in 10 ft. (6 mm in 3 m) and no more than 1/16 in. in 1 ft. (1.6 mm in 0.3 m) from the required plane, when measured from the high points in the surface. For tile with at least one edge 15 in. (0.38 m) or longer, the maximum allowable variation is no more than 1/8 in. in 10 ft. (3 mm in 3 m) and not more than 1/16 in.in 2 ft. (1.6 mm in 0.6m) from the required plane, when measured from the high points in the surface.
Given these standards, one would think that a good installation would be easily achieved, but that is not how it works in the field. The two most important requirements are for the substrate to be flat and clean. Unfortunately, this is where site conditions go wrong.
Getting the floor flat can be achieved most times with a good quality floor patch, or in really poor conditions, a primer and self-leveling underlayment will work. The real difficulty is getting the floor clean. The attached photo shows a really nasty jobsite that is unacceptable and should be rejected. Sure, you can scrape off the joint compound to get it looking decent, but will the patch and thin set mortar bond to it? Scrubbing the floor with a mop and water is probably the worst choice that could be made. The scrubbing does clean the floor, but the drywall dust and joint compound are now liquefied and driven into the pores of the concrete. At this point, the contaminated concrete may never yield a suitable bonding surface. If the surface is questionable, run a bond test. See if the thin set will bond. If not, walk away.
Sometimes the best jobs you see may be the ones that you did NOT get. Remember, the above-mentioned ANSI standard states, “Installation shall not proceed until satisfactory conditions are provided.” If you accept it, you own it. Think about it before you say, “Okay, I’ll do it.”
