Unlike many other flooring products, the rigid nature of ceramic tile does not allow it to conform to any type of surface irregularities. With each job, some means of correction will have to occur. Correcting out of plane (not flat) conditions requires careful evaluation as it can become very expensive in both product and labor categories. Retailers often wrongly expect that all the corrective measures required for providing flat lippage free tile work will be automatically included in the standard installation price and are often very surprised to learn there may be some additional charges.
Speaking for myself and others in the installation community, we try to be just as accommodating as possible but at some point we occasionally have to put ourselves in the uncomfortable position of saying there will be an additional charge for corrective work. So if making the floors flat is not our job just whose job is it?
Published recommendations for ceramic tile come from a variety of sources. The tile industry, through the Tile Council of North America (TCNA) and the American National Standards Institute (ANSI), provide the portion related directly to our trade and are known as the TCA and ANSI Handbooks.
Part of those recommendations are that floors and walls be on plane or “flat” within 1/4” per 10-ft. and have no greater variation than 1/16” in 12-inches. Tile floors and walls do not have a level requirement, only a flat or “on plane” requirement. These recommendations are based on the standards published by the trade associations responsible for those substrates.
You will also find similar reference for tolerances in a document published by the American Plywood Association (APA or Engineered Wood Association) known as the Design Guide (available at www.apawood.org). APA recently became the accredited standards developer for wood products by the ANSI.
For gypsum wall products, the tile industry draws the recommendations from a document known as GA-216, published by the gypsum industry. Flatness requirements mentioned in the TCA handbook are not TCNA recommendations; rather, they are adapted from those who provided the substrates. For those of us doing new construction under contracts and with specifications, those documents are your bibles.
But what about remodeling and renovation? In the real world referenced or not, expectations still exist - people want and expect flat floors free of lippage. Here the installer assumes the responsibility of correcting any tolerance deficiencies that may affect the installation. His guideline comes from references made to standards or manufacturer recommendations printed on nearly every bag, bucket, or box of setting materials and related items I have ever seen, with few exceptions.
Let’s just forget about who is responsible for what for the moment and focus on the basics. Bottom line: customers want flat floors free of any lippage. They want floors with very small grout joints perfectly aligned, straight as an arrow for long distances. The feeling is the tiles are bigger so the work is less. There are a host of problems with that theory. Anyone who has ever installed large tile knows the bigger the tile, the more work to get it installed properly. We can purchase high quality or “rectified” tile and eliminate size issues, but unless we have a perfectly flat floor, there are going to be both alignment and height variation issues.
Occasionally, an installer will attempt to use standard thinset to flatten the floor. Once you get over 3/8 to 1/2” thickness with a standard thinset, most have a very low bond and compressive strength. Medium bed mortar that can go up to 3/4” thick are helpful, but it can be very time-consuming to set each piece flat to the adjoining tile when you are properly bedding the tile.
Often, you will also find a substantial elevation change when you work your way across the room to another doorway that brings a new problem - I’ve been there myself. Mortar beds have always been a traditional way of providing excellent flatness and bonding surfaces for ceramic tile but few projects are designed to accommodate the height and or weight of a mortar bed. This brings us to a practical solution to accommodate the needs of the installation and skills of the installer, self-leveling products.
In doing a little research on the current stable of products available in this category, it was clear that each product in a manufacturer’s line has different attributes. My original intention with this article was to describe some commonality shared by all self-leveling products.
It is accurate to say that none of the six manufacturers reviewed for this article shared the exact recommendations in surface preparation and mixing. The only commonality I could find between manufactures is they all call this pumpable or pourable product self-leveler. These are all highly engineered products with very specific performance parameters so when choosing a product, chose wisely
These products tend to be on the finicky side and are unforgiving of error. Priming the surface to be covered is a key component in the success or failure of product application.
We always talk about the proper water ratio for thinset and its importance. Many dismiss it because they can still achieve some bonding value. Proper water ratios cannot be dismissed with self-leveling products, they won’t bond.
Most self-leveling products are also sensitive to slab moisture. If a slab has an elevated moisture and pH level there will likely be bonding issues with most products. Expansion joints must also be carried through the topping. When used in wood structures, there are numerous cautions. Almost without exception the use of a reinforcing product is mandatory though recommendations vary with both the service requirement of the floor and manufacturer of product. A thin cement topping also needs room to move with the downward deflection of wood substrates.
Perhaps the biggest misconception of self-leveling products is that they actually level themselves. Not quite.
As wonderful as these products can be, getting paid appropriately for their use has always been a problem. It is very difficult to calculate the exact amount volume of material required to provide coverage for any given area. Making assumptions can be very hazardous to your financial well being when using a product with the consistency of soup. We have even gone as far as taking elevation readings all over the room using a laser and still been off on our calculation enough to hurt a little so always err on the side of caution.
Once the skills and technique are mastered I think you will find this is a much faster approach to correcting floor problems than squaring each tile up to the other with the appropriate thinset mortar. It is also much easier to get compensated for as the customer can see there is some corrective work going on that cannot be as easily perceived when adding additional thinset to make up for tolerance inconstancies in the floor. While this approach may not work for everyone, our company found it to be very profitable and that’s why we work.