Getting the coverage to provide full support on larger tile can be difficult to achieve using conventional thinsets without backbuttering. Some of the newer thinsets on the market are thixotropic. During installation, a thixotropic mortar decreases in viscosity while being set. Once the tile is placed, the viscosity increases making coverage easier to obtain. Photo courtesy MAPEI.
According to Commerce Department statistics, this year has been relatively flat for the tile industry, with sales down 40% from peak levels achieved in 2006. Many companies have gone through all their financial reserves and are desperately looking to generate some cash flow.
The continued lack of opportunities has created intense competitive pressures when a job comes up for bid. This is forcing many within the industry to consider expanding into uncharted territories to create additional opportunities.
While floor covering dealers long ago integrated ceramic tile into their product mix they stayed mainly in the residential sector. Now with a vast inventory of unsold new homes, an additional one million homes in foreclosure and a similar amount headed that way or underwater, residential work is at a trickle compared to the 65 to 70% market share it typically represents. This has forced many tile and floor covering stores to look at the only construction market still showing some signs of life – the commercial segment.
Regardless of the type of mortar used, directional troweling should be used. When tile is placed perpendicular to the ridges and rubbed across them, the air under the tile has a means of escape and thus allows for better coverage. Photo courtesy Laticrete.
When projects are loosely specified with such basic terms as “thinset mortar must meet ANSI A 118.4,” things can quickly degrade to a point that even the famous “value engineering” would not allow. Those understanding there are different performance levels within that specification find themselves at a competitive disadvantage unless they follow the herd.
For this reason, though they shouldn’t be closely related, the words thinset and economics have become increasingly intertwined. In looking at places to save and submit the lowest possible bid, some mistakenly think thinset is one of those areas where it won’t make that much difference. Thus they use the lowest priced material available meeting the referenced standard. It is easy to understand why. For many years cement-based thinset mortar was either modified (118.4) or unmodified (118.1). The only change since those original standards were created was the addition of a thinset for direct bond to plywood (ANSI A118.11).
Thinset mortars have continued to grow in both numbers and complexity. In checking various manufacturer product lines you will typically find two or three ANSI 118.1 mortars, 15 to 20 ANSI 118.4 mortars, and about half of them meeting ANSI A118.11 standards.
Even the most studious tile person often has trouble distinguishing one mortar from the next, but there is a specific product performance criteria for each and every product made. Unless you are very technical and uncommonly learned, it is likely you would have to ask the reason why you should use one product over the other as they all meet ANSI A118.4.
Non-sag mortars use several different technologies. It is quite possible to install an 18” tile with no slipping. It has become one of my favorite demonstrations. There are no tricks; just follow the instructions on the bag. Photo courtesy Laticrete.
Floor prep has always been hated and feared by floor covering installers, in particular ceramic tile and stone installers. While carpet, vinyl, and to some extent laminates and wood are applied with adhesives sticking to nearly anything over undulating surfaces, the same cannot be said for tile and stone products.
Cement-based thinset mortars require a clean, abraded, absorbent surface to be successfully applied with any longevity. Nothing sticks to shiny slabs and if it does, it won’t be for long. Slabs should have a steel trowel and broom finish, void of curing compounds or any other substance that would interfere with cementious bonding such as paint overspray. If not, they need to be cleaned and abraded to remove any contaminates and open the pores.
The easiest way to see if a bonding problem is on the horizon is a water drop test. Water allows the cement to develop its structure. If the water does not go into the slab, the bond will be either weak or nonexistent, depending on the severity.
To test, sprinkle a few drops of water on the slab. Watch to see if the drops are absorbed. This will give you some indication if the slab is ready to receive cementious bonding materials. My own personal and unscientific rule: Zero to five minutes for absorption I am happy; more than 5 minutes and I am concerned and going to use a better thinset. If it is more than 10 minutes somebody is grinding that slab or I am going home.
By the way, acid will not solve this problem and quite likely create new ones. I have plenty of pictures to prove it.
Under the best of circumstances, once the floor is clean you are ready to go. Unfortunately with the size of tile in use today that is rarely the case. Standard tolerances for slabs to receive ceramic tile are 1/4” in 10’ with variation not to exceed 1/16” in the desired plane. Notice the word is plane, not level.
Recent changes in tile industry standards note that the 1/4” in 10’ tolerance only applies to tile where the longest edge is 15” or less. Newly published standards require a slab tolerance of 1/8” in 10’, with no greater variation than 1/16” in 24” for tile with an edge greater than 15”.
Rather than correct the floors with a suitable product, we often see the tile installer trying to correct out of plane conditions with thinset mortar. Thinset mortars are not designed to level or flatten floors nor are standard thinset mortars rated for use in a thickness greater than 1/4” after embedding the tile.
Medium bed mortars are designed to minimize slump and facilitate thicker bond coats, as compared with non-medium bed or standard mortars. These characteristics make them useful for setting heavy tiles and/or tiles with ungauged thickness and for setting tiles with at least one side greater than 15” where the final thickness of the thinset mortar will exceed 3/16” under the tile.
For a number of years now an ISO standard for thinset mortars has been available. In my opinion it still has some category shortcomings however it does offer a substantial means in controlling the quality of the products being used. Reference to the ISO 13007 thinset designations are listed in the current TCNA handbook.
Currently medium-bed mortars are defined as such by their manufacturers. These mortars do not have unique ANSI or ISO standard designations to characterize them. That is an issue currently being addressed by the standards committees and will hopefully soon be resolved. Limitations of space will not allow me to delve into all the other specification ills of our current standards system using only ANSI A118.4, so it is time to pick one performance area and for me that would be deformation.
Tile installed in slab on-grade applications is subject to minimal needs when it comes to deformation. Tile installed over slab on deck (suspended slabs) and in wood structures have a great need for deformation abilities. By design all above-grade slabs and wood structures move. The thinset you use for above-grade applications certainly should exceed the values of minimal base grade material. There is no guidance under ANSI standards for deformable thinset mortars. Manufacturers refer to these as flexible mortars. There is some guidance provided under ISO (International Standards Organization) on thinset mortars for certain performance attributes, but not in the medium bed category as mentioned earlier.
Tile, grout, and bonding materials have grown increasingly complex. Claims are increasing due to poorly skilled installation and loose written specifications. My recent personal experience is many of those who have bid too low using minimalist products improperly applied are no longer with us. Is it really worth taking a chance with product performance?
