QUESTION

Recently we found polished porcelain tile, 300 x 600mm and 600 x 600mm bent (4 corner sides concave) after de-bonding. We have sent tile to do water absorption, moisture expansion and thermal shock. All passed ISO 10545 standard. Mostly tile de-bonding between half year to 4 years, site applied 2-3mm laying gap.

Could i know it would be tile quality? cement high shrinkage issue? movement? I have some photos to show you if needed. Would much appreciated if Sir could help.

ANSWER

ANSWER - Considering it is a porcelain tile, I would think that the warped corners were that way when they were installed.   Porcelain tiles are not moisture sensitive and they would not be expected to warp after they are installed.  Having all 4 corners of the tile concave would be considered excessive warpage by USA standards.

A 2-3 mm grout joint is normally reasonable for a rectified porcelain tile installed in a soldier course pattern (tiles are not off-set from each other).

The debonding of the tile should not be due to the tile unless the tile had some sort of contaminate on its back side that prevented the tile from achieving an adequate attachment to its substrate.

Generally speaking the reason tiles debond is because they are not bonded as well as they should be to their substrates and due to the tiles being subjected to some stress that is greater than they can resist.   If the tile had a contaminate on its back side that acts as a bond breaker or if the substrate to which it is attached has a contaminate that acts as a bond breaker or if the adhesive is not suitable for bonding the tile can all be a possibility of why the tile was not better bonded to it substrate.

Tiles inherently are subjected to movements and resultant stresses caused by moisture or temperature or caused by dynamic structural movements within the floor assembly.   That is why it is required to have movement joints filled with a resilient sealant at all perimeters and transitions.  Per Canadian standards, movement joints should be installed within the field of tile every 4800 mm to 6100 mm in each direction for interior applications.   And installed every 2440 mm to 3600 mm for exterior applications and interior applications exposed to moisture and direct sunlight.

If there was new concrete installed that hadn't cured for at least 28 days at reasonable temperatures then it can have shrinkage that could subject the tile to more stress than it can resist.  If the cementitious adhesive was excessively thick it can have excessive shrinkage that can contribute to the problem.

The only way to determine the cause of the problem is to perform a forensic investigation and look for evidence that will explain what caused the failure.   If you don't know what caused the failure then you take the risk that the problem can reoccur when you replace the tile.