Monday, 4 March 2013

Understanding Tile Tenting Complaints

Tenting and delamination are the terms used to describe what happens when an area of tiled floor lifts centimetres off the substrate beneath. In the tile business the phenomenon is called tenting when the tiles lift, because the lifted tiles look like rows of peaked camping tents. The forces involved can be extremely powerful. In the photo above you can see the tented tiles lifted up an entire store gondola! When the tiles simply come free from the substrate without tenting it is called delamination. Close inspection often shows that more than one area of the floor has delaminated. Several sections might have lifted, not necessarily simultaneously but very close to it. And then, at times the delamination is only apparent when the floor is tapped upon or when someone walks across it wearing hard shoes and the floor doesn’t sound solid but rather hollow instead. As with most complaints tenting is generally caused by poor installation technique.

There are several reasons why a tile floor might delaminate:
  • the floor might not have been cleaned prior to tile installation;
  • the setting mortar might have partially dried before the tiles were placed in it;
  • the tiles themselves might have had dust or other contaminants on their backs.
The main reason, however, that tiled floors delaminate and tent is because of a lack of movement accommodation. Tiles have a different rate of expansion and contraction (the coefficient of expansion) than concrete for example, the material that ceramic tiles are often installed directly upon. Other common tiling substrates will also expand and contract differently than ceramic and stone tiles.

Concrete expands and contracts more than many other tiling bases. The difference between concrete’s rate of expansion (and contraction) and that of ceramic tile is about 10 to 1. A concrete slab one hundred feet across can grow and contract over half an inch. It only takes a fraction of that movement to cause a tile floor to delaminate. Knowing this, tile setters employ breaks in tiled floors to accommodate that movement. These are called movement joints and are placed at specified intervals to divide large tiled surfaces into smaller expanses and thus lessen the effect of substrate movement. The joints are then filled with flexible material instead of tile grout.

In addition to movement joints in the tiled field, perimeter movement joints are used where tile floors abut impediments to movement, i.e., walls, cabinets and the like. Whereas smaller tiled floors may not need movement joints in the field of tile, all tile floors need perimeter movement joints and it is the lack of perimeter joints that most often contributes the greatest causal force to a tented floor, even though other factors; contaminants, skinned over setting mortar and other installer errors, may come into play also. The fact that I used concrete floors as my example doesn’t eliminate other tile substrates from the need for movement joints.  All substrates move, albeit some less than others. Cement backer board, for example, is an excellent base for ceramic tile when the board is properly installed, but movement joints must still be provided. Various tiling membranes, both sheet and semi-liquid, can further improve longevity of tiled floors over any substrate, but every manufacturer of such membranes will specify that movement joints be employed.

The clause in our disclaimer pertinent to this issue reads as follows:
"When tiling large areas allow for expansion joints, generally every 5x5m area. Ensure that perimeter joints are in place and free from any adhesive and or grout."

Even in tough environments, properly installed tile floors with movement/expansion joints will last virtually forever.