The designer trend towards tiles and stone that are larger and have fewer grout joints continues in 2018. Many new sizes such as 60x60cm, 75x75cm, 90x90cm, 120x120cm and larger in both natural stone and porcelain tiles have become popular. Along with these new panel formats, the more stringent requirements for substrate flatness, anti-fracture membranes, proper setting material systems and expansion joints layout must be followed. Experienced installers and installation tools have also become more specialized and are vitally important for a successful, attractive installation.
The preparation of the substrates is a key factor in the overall successful outcome. Both floors and walls must be flat to 2mm across 3049mm at the maximum. These strict criteria are necessary to avoid any lippage between the tiles. Lippage is a dangerous trip hazard on a floor and must be avoided.
In new construction for floors over concrete, where possible specify to allow for a depressed slab of 2-3 inches. The tile or stone is then installed into a mortar bed (a mix of sand, cement and a binder) over a 6mm poly slip sheet. This installation method is more than 2,000 years old and allows for plenty of room to adjust for any unevenness in the subfloor and achieve a beautiful flat outcome without any trip hazards. With an average cost of about $1- $2.00 /sqft labour and materials it is a very economical solution.
For retro fit installations several options are available. Self levers are often used as option. Many allow for build ups from a feathered edge to 12mm thick. These options may be used over old adhesive residue, existing tile and other difficult substrates (consult your mortar systems supplier). The average cost ranges to about $3.00/sqft labour and materials.
For both new and retro fit installations both bonded and unbonded anti-fracture membranes are available. These membranes allow for independent movement between the tile and substrate. The unbonded version simply floats atop the exiting flat subfloor and the tile is bonded directly to the membrane mat. This system has the benefit of being laid out over substrates that are difficult to otherwise tile over such as old vinyl and linoleum floors, old painted or treated concrete. With often little or no floor prep, these systems save time and time is money. The bonded option is installed on to the subfloor with either a mortar or a special adhesive on the level or leveled substrate.
Walls must be equally flat to the same tolerance as floors with the added criteria of being sturdy enough to support the weight of the massive slabs. It will be likely that both existing and new walls will have to be parged flat to meet flatness requirement. Cement board or similar CBU have a better stiffness and are preferred for these large panels
New technology in mortars has advanced along with the growing tiles sizes. Many manufacturers have developed systems to support these heavier tiles. Installers require increased working time to comb the mortar over the substrate and back butter the tile. Also, increased non-sag capabilities are important factors when installing walls and floors. Often the tile suppliers will have recommendations for the proper installation products and systems to follow. Your supplier partners want you to be successful so follow their guidance. Keep in mind that these are new, very large panels to install and many installers have never seen a 75x75cm or 90x90cm tile before, whereas the tile suppliers consult clients and specifiers daily on their use and installation product requirements.
Plan to have perimeter joints and expansion joints as required by the industry guidelines in TTMAC detail 310MJ. The recommended spacing and sizes for expansion joints and control joints are as follows:
- for interior tile applications: the control joints must be spaced at intervals of 4800 mm to 6100 mm in each direction. The minimum joint width is 6 mm wide. In areas exposed to moisture or direct sunlight the spacing placement reduced to 2400 mm to 3700 mm apart in each direction. The minimum joint width is 6 mm wide. For above-grade concrete slab substrates again the placement is 2400 mm to 3700 mm apart in each direction. With a minimum width of 6 mm wide.
- for Exterior tile applications: due to high temperature ﬂuctuations, use a minimum 10 mm wide control joint spaced at intervals from 2440 mm to 3600 mm apart in each direction. In areas of extreme temperature variations (over 40ºC) between summer highs and winter the joint width shall be a minimum of 13 mm.
These large panel sizes will require new handling tools. Suction cups or an aluminium handing frame for moving these pieces are a must. Large portable light weight tile cutters and tile water saws are now available for the installers.
When all the pieces are properly in place, the finished installations are beautiful and long lasting.
Bill Wright is training and education, technical services manager at Stone Tile International.