Maxi Size – Flooring Installation Challenges
The trend for the size of floor tiles is expanding into very large formats of 600×600, 800×800, 900x900mm and the fabulous maxi formats of 600x1200mm and the plank size of timber looks and natural stone looks of 150×600, 200×900 and 200x1200mm. The look of these maxi size tiles is aesthetically pleasing, giving you a flowing open look with fewer grout joints. The benefit is easier maintenance resulting from fewer grouted joints. However these sizes present challenges and difficulties when used in floor installations. When you choose from the beautiful range of large format tiles, especially wood look plank shaped tiles you need to take into consideration the following so that you can achieve an absolutely perfect outcome.
The larger the format, the more possibility there is that they are not flat. This is not to say they don’t conform to the international standards, they probably do, but the very shape of these tiles makes their flatness all the more critical. Basically with these tiles, the center is higher, in other words, they are crowned in the middle. Some brands and types are worse than others. This becomes more of a problem when you offset (overlap) them. Variation should not exceed 2mm over the length but this is still enough to cause problems.
Lippage is the degree to which one tile rises above an adjoining tile. One of the implications of larger format 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 600 x 600 tiles, but when a tile is much larger or is cut to a plank format like a 150 x 900, the curvature in the tile can make a noticeable difference, especially if the planks are offset to each other. Along with smaller grout joints typically requested for wood look tiles, you end up with lippage.
What to Avoid:
INSTALLATION PROBLEMS WITH LARGE RECTANGULAR TILES LAID IN A BRICK PATTERN
It has been found that the surface flatness of some large format ceramic tiles can cause lipping problems particularly when rectangular tiles are laid in a brick pattern. Often large tiles laid with a brick pattern sees the highest part of any curvature correspond with the lowest part of adjoining tiles therefore accentuating lipping (see below)
By doing a 50% offset, where the middle of a tile is exactly in line with the grout joint of the next row, you maximize the amount of unevenness, or lippage, between the tiles.
Therefore it is best not to lay them with 50% offset but instead use the industry recommendation of an offset of no more than 33%. If an offset greater than 33% is specified, then specifier and owner must approve mock-up and lippage. That the manufacturer’s recommendation should be adhered to so that a good outcome can be achieved.
How much lippage is considered acceptable?
The allowable curvature for first quality ceramic tiles whether plain, polished or honed, according to AS4459 and the ISO standard remains at 0.5%. This allows a 600mm x 300mm tile to curve up to 3mm in its length and still be considered first quality.
Porcelain or ceramic plank floors can look good but the biggest problems with them can be avoided by simply knowing what to watch out for and planning accordingly. You’ll find that they should last a lot longer than their wood counterparts as well. With large format tiles, you want to use the best medium bed mortar and the correct trowel. With these types of mortars a 12mm x 12mm notch trowel would be the smallest size that you will want to try. Yes, this uses more thinset and yes, these types of mortars are more expensive, but this isn’t the time to skimp if you want well laid plank floors.
Medium bed mortars are a common solution to support large format tiles and prevent lippage. These mortars are formulated to keep the tile from slumping into the mortar bed and to not shrink as the mortar cures. Medium bed mortars may require a polymer additive to bond with some substrates. Because medium bed mortars can be difficult to trowel, installers often add more water, which can adversely affect the mortar’s non slump performance and its bonding ability.
New types of performance mortars prevent large format tiles from slumping and are easier to use than traditional medium bed mortars. Some of these mortars are formulated with hollow, ceramic microspheres that are not only lighter in weight but produce a ball-bearing effect – resulting in minimal trowel resistance and better labor productivity. The microspheres also provide buoyancy, which helps contribute to the non slump properties.
Subsurface Tolerances for Thin Bed Methods. For thin bed ceramic tile installations with tiles at least one edge 45cm in length or longer, a maximum allowable variation is 3.2mm in 3m from the required plane, with no more than a 1.6mm variation in 60cm when measured from the high points in the surface.
For subsurface tolerances with the thick bed mortar, or self-leveling methods, maximum allowable variation in the installation substrate is 6mm in 3m. Fortunately, there are several systems available to help the tile setter to minimize lippage. These systems work on floors, walls and ceilings.
Tile weight is also a major challenge. Heavy floor tiles that settle into the mortar bed can cause lippage. The result is a finished surface that has an uneven appearance. In the 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. Working with large format materials requires tighter tolerances in the substrate. In addition, its weight makes it harder to handle in both floor and wall applications.
Advanced installation materials and techniques have improved the overall quality of large format tile installations while helping to improve the installer’s efficiency. Keeping up with the latest in products and techniques will help installers produce aesthetically pleasing – and profitably installed – walls and floors.
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.
Remember that there are many satisfied customers that have already installed large format tiles. If you are still not sure about choosing large format or plank tiles speak to TFO today so that you can be reassured that your choice will have the best possible outcome.