What is causing my Ceramic Tile to Buckle / Tent up?

QUESTION

My condo was built 11 yrs. ago. I’m the original homeowner. The ceramic tile in my kitchen & connecting sunroom is “tenting” and the buckling /tenting is spreading. The tile floor is over a floating concrete slab. Up to 6 professionals visited/inspected only to remark they’ve never seen anything like ceramic tile buckle. I personally learned the term tenting via google. Everyone is eager to get hired to rip up and install a new floor. However, I cannot afford to put a band-aid over the problem which can reoccur. I need someone’s help to figure out the real source of the problem. I feel the problem is related to a moisture issue, but how do I determine the source? My new exterminator said every bug I’m having a problem with likes moisture I.e.: earwigs, centipedes, silverfish, spiders, etc. I don’t know who to trust or what to do next to correct this frustrating problem. Please help!

ANSWER

ANSWER - When tile debonds and buckles up we do refer to that as tile tenting.  The cause of tile tenting is normally due to several compounding conditions.  First is that normally the tile installation does not have any movement joints, or not enough movement joints, to allow the tile to expand.  There should be perimeter movement joints at the walls and other restraining surfaces, and at least every 25 feet for interior applications.

If the ceramic tile has a porous clay body, then it is more susceptible to moisture or high temperatures causing the tile to expand.  If there are no movement joints when the tile expands then it is constrained and the tile is subjected to an upward force that can cause it to debond.  Once the tile debonds it relieves the stress in the tile that results in the tile tenting up.  If the tile isn't bonded very well to the substrate, then it will have a greater propensity to tent up since it can't resist the stress as well as a well bonded tile.

Not sure what you mean by a floating concrete slab.  Perhaps that there are no footings to the concrete slab, which doesn't seem reasonable.  Or maybe you mean there is a cementitious mortar bed over a wood subfloor?

If the concrete slab is installed over a ground without a vapor retarder that keeps the water from the ground from migrating up through the slab, then that might be the source of the water.   So high moisture with a non-vitreous porous tile means the tile will expand.  If there are not any movement joints and if the tile isn't bonded well then you will likely get tile tenting.

You could try repairing it by removing the tented tiles and letting it dry out to see if they will fit back in.  Then cut in movement joints at the perimeters.  More than likely you need to replace the tile floor, but with the new installation install a moisture barrier over the concrete slab and then adhere the tile to it.  Plus install the movement joints.  If you replace the tile with a porcelain tile that is impervious then it won't be as susceptible to expansion from moisture.

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