Successful Ceramic Tile Installation

The importance of underlayment: It's what is underneath the tile makes all the difference.

Most tile failures can be attributed to incorrect installation.

Properly installed, a ceramic tile floor should provide years of service and beauty. While vinyl floor coverings will be replaced several times, a ceramic tile floor is installed once. What makes for a successful installation?

The importance of the underlayment

Too often ignored by the non professional installer, the underlayment is key to the longevity of a ceramic tile floor. It is the foundation; and, just as you wouldn’t build a home without a firm foundation, this important part of a ceramic tile installation should not be omitted either. Unfortunately, some floor covering retailers and installers will still tell you that underlayment is not necessary if you have a sound subfloor. Don't be fooled! Your existing subfloor does not by itself offer proper support for ceramic tile, and secondly, underlayment is not intended to compensate for an unsound subfloor. In addition, it is difficult to achieve the proper bond to wood. Even though adhesive products are sold for installation of tile over plywood (fir plywood only), most professionals in the industry advise against this practice.

We have seen countless new homes that are under five years old with failed tile installations because the contractor, not interested in quality construction, but only “cheap”, omitted this important part of the floor “system”. All too often they will simply lay tile directly on the plywood subfloor. If this isn't bad enough, the type of plywood used for the subfloor is not of the correct type for a tile-over-plywood installation, which must be fir plywood, with no voids. As of this year, 2008, we are still seeing this in our area. The result of this practice is predictable. Failures include, cracked tiles, loose tiles, loose grout, or all three. At this point, all that can be done is to remove the tile, install the proper underlayment, and lay new tile.

Especially in wet areas, such as a kitchen or bath, underlayment is essential, as moisture that may be absorbed into the wood subfloor will cause the tile to separate from the wood, and the grout will begin to come loose. Often, the tile will crack due to improper support. Once again, even though adhesive products are available for setting tile over exterior grade plywood, this may mean the difference between a 3-5 year installation and a lifetime installation.  Additionally, mold and mildew, which may grow underneath the tile as a result of the plywood becoming saturated, may present a health risk.

Underlayment must be set in a mortar bed

This is not optional, and it is another one of the most common installation errors that we find. Even though underlayment may have been installed, it has not been set in a mortar bed, but fastened directly to the subfloor. This is often the case when the General Contractor installs the underlayment ahead of the tile contractor (which should not be the case, because, in the end, the tile contractor is responsible for the quality of the installation). Nevertheless, we have seen this countless times in our area of North East Ohio. Builders in our area routinely omit this important step. This is also the mark of what we call the “handyman job”, as the nonprofessional will usually skip this step too.

Not setting the underlayment in a mortar bed may be only marginally better than no underlayment at all, and will lead to failure of the installation. All  CBU (Cementitious Backer Unit) manufacturers clearly state in their literature that the product must be set in a mortar bed. Omission of this step by a building contractor can only be due to laziness, or a means to cut installation time and cost at your expense. This is not done for purposes of bonding. The mortar is for support, and as a filler, so that there are no voids under the CBU.

One homeowner, who consulted us about a failed tile installation done by the home improvement store, told us that the contractor from the “big box store” that did the installation had glued the cement board down with construction adhesive and told the homeowner that this was “accepted practice”!  A mortar bed is the only accepted method for installation of cement board.  It should also be noted that the mortar is not intended as an adhesive; it is there to provide continuous support for the board with no voids.  It is the fasteners which secure the board to the sub-floor.

Finally, the underlayment must be fastened according to the manufacturers specifications. For cementitious backer boards, this means 1-1/2" galvanized roofing nails, or specially made screws for CBU, every eight inches in each direction. Not drywall screws!  Drywall screws are not acceptable fasteners for cementitious backer board.  They do not have a large enough head to properly secure the board. Further, it is difficult to install them flush with the board's surface, and they are subject to deterioration from the alkali in the mortar. This is another mark of the nonprofessional installation.

Unfortunately, these problems are all too common with new construction in our area. There are still far too many installers and home builders who will tell you that underlayment is not necessary, or will install it incorrectly, with no mortar bed and incorrect fasteners. We have even seen staples used! Do not be fooled by their claims that they “have never had a problem”. Do not accept this. We have seen the resulting problems time and time again, long after the contractor is gone; cracked tiles, and loose tiles and grout.

Important: No contractor or installer that is familiar with ceramic tile and tile installation methods and practices, would omit this important component of the tile “floor system”.

It is your floor.  Insist that it be done in accordance with industry standards. If you are building a home, make sure your contractor does not skip this.

Beware of the “Jersey Mud Job”

Recently we have run into a method which the homeowner has been told is a “mud job” by the installer, who leaves the impression that this is better than cement backer boards, and may also tell the homeowner that this is the “old method”.  Disparagingly referred to as a “Jersey mud job”, or sometimes, “Cleveland mud job” by tile professionals because it's popularity seems to be regionally confined to these areas, this method involves stapling expanded metal lath to the floor and troweling mortar into it, thus producing a thin (approximately 1/8") bed. The tile is then set as usual on the surface thus created.

Warning! This is not a Tile Council of North America approved method, and bears no resemblance to the old mortar bed method (which required a thick bed), but is simply a shortcut which cuts installation costs, and only serves to save the installer time and money, at your ultimate expense. It is very cheap and it goes down fast, but reports from the field by other tile professionals who are industry leaders, indicate that the failure rate for this kind of installation is extremely high, and for this reason, this method is not approved by The Tile Council of North America (TCNA), which sets the standards for ceramic tile installation methods and practices.

The only cement mortar and metal lath method which is approved by TCNA (Method F145-02), requires that the mortar bed be not less than 3/4" thick for areas up to 100 sq. ft., and not less than 1-1/4" thick for areas greater than 100 sq. ft. In view of these requirements, one must conclude that the thin bed method described above is inferior, and will likely result in failure of the installation.

If an installer tells you he is going to do a “mud job”, ask the installer how thick the mortar bed is that he plans to install. If it does not meet the above specification, politely show him the door.