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Saw-cut joints in concrete
QUESTION
I am tiling a concrete floor that has cracks or saw-cut joints in it. How do I treat those joints, and do I have any liability if the tile cracks over it?
ANSWER The NTCA always encourages individuals to do tile installations in accordance with the standards and guidelines found in ANSI (American National Standards Institute) and the TCNA (Tile Council of North America) Handbook for Ceramic, Glass, and Stone Tile Installation.
The TCNA Handbook has a section exclusively for movement accommodation joints. That section is referred to as EJ171. The information in ANSI is found in ANSI A108.01.5.
There are crack-isolation membranes on the market to allow for installations to be done over cracks and some joints in concrete. There are both liquid-applied and sheet-applied membranes that could work in your situation.
Crack isolation membrane from Custom Building Products.
The standards for these membranes are found in ANSI A118.12. The ANSI standards for crack isolation have two levels – one for cracks less than a 1/16" and one for higher performance with crack movement up to 1/8". EJ171 states that when crack-isolation membranes are specified and used in accordance with manufacturers’ instructions, the tile contractor is not responsible for cracking in grout joints or tile where the installation has been over any such relocated movement joints.
The TCNA Handbook shows method F125 as an option, which employs the crack-isolation membrane and moves the sealant joint to both sides of the crack. You would have to work with a manufacturer of crack-isolation membrane to follow their instructions to receive their manufacturer warranties.
Grout selection
Question
I have a customer who bought a cheaper tile for a rental property of theirs. It has a lot of differences in size and seems to be somewhat out of square. They want to use black grout to prevent staining. I think with all the differences between the tile and the contrasting color the installation will look poorly no matter how much time I spend on it. Do you have any information I can give my customer about this?
ANSWER
Grout color selection will make a big difference in how the final installation looks. The NTCA Reference Manual backs you up.  Chapter 10 on Grouts states:
“Selection of a grout color that contrasts with the tile will emphasize the grout joint and correspondingly any variations in tile size and position. Selection of a similar or complementary grout color will de-emphasize such variations.”
The grout selection guide in the TCNA Handbook adds:
“When a similar color grout is used, it is often more difficult to see the haze left after initial grout cleaning and extra care must be taken to remove all haze.”
You may want to let your customer know that grouts contain more latex and polymers than in the past and are a lot more stain resistant, and now there are many single-component grouts on the market that perform comparably to epoxy in stain-resistance testing. I understand this is for your customer’s rental property but I would also explain it is important to purchase and install tiles that have been tested to meet industry minimum requirements for size, and shade deviations, as well as wedging and warpage. All these standards and many more are found in ANSI A137.1.