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.
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.
