Challenges with Large Format & Plank Tile.

Flooring installation challenges

Large-format tile and wood-look long plank tile presents several challenges when used in floor installations. Some of the common concerns are described below. As a supplier you should advise your customers and installers of the possible difficulties.

Lippage 
Lippage is the degree to which one tile rises above an adjoining tile. One of the implications of larger format tiles, even simply longer tiles is the likelihood of more lippage. You might think that if the substrate is flat you shouldn’t have to worry about lippage but the fact is that the tiles themselves are not perfectly flat either. You won't notice this so much with square 60 x 60cm tiles but when a tile is much larger or is cut to a plank format like a 15 x 90cm the curvature in the tile can make a noticable difference, especially if planks are offset to each other. Along with smaller grout joints, typically requested for wood look tile, you end up with lippage.
Sometimes customers request a 50% offset however you should know that the industry recommends an offset of 33% or less on larger tile.

The ANSI A108.02 recommendations regarding grout joint size, particularly in relation to the tile size, dimensional precision and offset pattern are that where the running brick joint offset is 45cm (nominal dimension), the running bond offset will be a maximum of 33% unless otherwise specified by the tile manufacturer. If an offset greater than 33% is specified, specifier and owner must approve mock-up and lippage.

The Tile Council of North America (TCNA) Handbook for Ceramic, Glass, and Stone tile installation states that the factors that influence lippage are: 

• Allowable thickness variation in accordance with manufacturing standards.
• Allowable warpage of tile modules.
• Spacing or separation of each tile module, which would influence a gradual or abrupt change in elevation.
• Angle of natural or manufactured light accentuating otherwise acceptable variance in modules.
• Highly reflective surfaces of tile modules accentuating otherwise acceptable variance in modules.

How much lippage is considered acceptable?
The TCNA Handbook states: For pressed floor and porcelain tiles with a joint width of 1.6mm to less than 6mm, the allowable lippage is 0,8mm. For 6mm or greater, allowable lippage is 1.6mm.

Now we know the acceptable lippage, but what about floor flatness? The TCNA Handbook states:
Subsurface Tolerances for Thin-Bed Methods. For thin-bed ceramic tile installations with tiles at least one edge 45cm in length or longer, maximum allowable variation is 3,2mm in 3m from the required plane, with no more that a 1,6mm variation in 60cm when measured from the high points in the surface.
For Mortar Bed Methods. For subsurface tolerances with the thick-bed mortar, or self-leveling methods, maximum allowable variation in the installation substrate is 6 mm in 3 m.

Fortunately, there are several systems available to help the tile setter to minimize  lippage. These systems work on floors, walls and ceilings. Two examples of typical systems are shown below.


Other risks.
Tile weight is also a major challenge. Heavy floor tile that settles into the mortar bed can cause lippage. The result is a finished surface that has an uneven appearance. In a worst case, it is an uneven floor that causes a tripping hazard.

A substrate that isn't perfectly flat to begin with will exacerbate an uneven floor problem as the tile is installed. 

In addition, it is crucial to achieve secure bonding of the substrate and the tile flooring. Applying an insufficient amount of material may result in hollow sounding spots. The hollow spot is susceptible to damage from concentrated weight because of a lack of support from the mortar in that area of the tile.

Cracking is a possibility if the tile is bonded directly to concrete. This is because cracks naturally occur as water in the concrete substrate evaporates. These shrinkage cracks can transfer from the substrate and into the bonded tile. Cracking can also occur from improperly installed wooden subfloors.

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