QUESTION

Why is my ceramic tile grout cracking and tile tenting? - I own a townhome in Rockville, MD, just outside Washington, DC. In Aug 2010 I replaced the existing kitchen linoleum floor with porcelain tile. The substructure of the kitchen floor is floor trusses @ 19.2" on center. Our contractor installed Hardiboard under the tile on top of the plywood deck. Over the last few months, we have observed substantial cracking in the tile grout (no tile has cracked yet) and in one area two adjacent tiles have "tented" after separating from the hardi board. We have spoken with our contractor and would appreciate your input as to a proposed solution, hopefully the least radical. We would be happy to pay for one of your experts to come and do an on site inspection.

ANSWER

ANSWER - I understand that you have a townhome where you replaced your kitchen floor with ceramic tile in August 2010.  The tile was installed over hardibacker board that was applied over a wood subfloor over floor trusses @ 19.2" on center.  Over the last several months you have substantial cracking in the grout and two tiles have debonded and tented up.  You would like to consider retaining our services to perform an inspection to review the conditions and determine the cause of the problem, determine if the installation is within industry standards and the standard-of-care for professional installers, and to determine what will be required to remediate any problems.

We do have extensive experience at investigating floor tile failures similar to what you have described.  Generally speaking when there is a problem or failure it is never due to a single defect, but rather due to compounding defects.

There are several likely compounding problems.  It sounds like there could be excessive movement in the floor as suggested by the cracked grout.  The spacing of your floor joists are not necessarily a problem, but the overall floor assembly could be structurally deficient.  You need to consider the properties of the plywood or OSB or ? subfloor and how it was installed and fastened.  You need to consider the rating of the trusts and how they were braced and installed.  You need to consider the thickness of the hardibacker board and how it was installed and fastened.

The fact that you have tented tiles suggests that primarily the tile was not well adhered, and that there could be excessive deflection in the floor and that there probably are no movement joints built into the tile assembly.  Why the tile was bonded better could be for many other compounding reasons.

Of course to properly remediate your problems would require fully understanding what caused the problem so it can be properly remediated and you can avoid subsequent problems if you only treat the symptoms rather than the problems.  To find out more about our inspections services, please visit www.CTaSC.com