Features

An ideal ceramic-tile base

by Morris and James Carey
Friday March 08, 2002

Our father, although he had never worked in the trades, definitely was a handyman’s handyman. He loved his workshop. He favored plumbing, painting and carpentry, but was hesitant about doing electrical work. And, we never saw him do ceramic-tile work. 

As we have developed our own interests in construction and home improvements, we have discovered that our father’s fear of ceramic-tile work was not unfounded. Tiling is fun, but some tasks, such as those requiring intricate tile cutting and notching, can be very difficult. Also, some types of tile are more difficult to install than others. 

Generally speaking, the larger the tile the easier it is to install. This is because when large tiles are used, fewer have to be installed to cover a given area. This means less cutting, less grouting and less chance for mistakes. Tiny tiles are extremely hard to install because there are so many lines to consider, straighten and grout. 

The big problem with installing tile — even with the small jobs — is the unevenness of the surface (countertop, wall, ceiling or floor) to which the tile is going to be applied. Tile seems to exacerbate waviness in a surface. Most uneven surfaces look worse after tile is applied. In a home, practically every surface is wavy to some extent. Mortar is used to correct this kind of problem. Mortar is a substrate that can be made to be perfectly smooth no matter how wavy the surface. In short, troweled-in-place mortar is a backing that adds strength and smoothness for tile. A mortar bed can be built to work over a waterproof layer, like in a shower. 

First, a waterproof membrane is installed, then the mortar bed, and finally the tile and grout. When the grout fails and water gets behind the tile and mortar, the waterproof membrane protects the framing. All of these layers make tile in mortar very expensive. 

Thirty years ago, builders decided to try a new technique — tiling directly to wallboard. No mortar. At first everything looked great and tile showers in modern subdivision homes were selling like hotcakes. Soon after their warranties ran out, these unlucky homeowners were spending big bucks repairing those tiled showers. Before long, folks were discovering that tile-on-wallboard wasn’t a good application. Soon after, better building departments started to outlaw the technique. Before long it was apparent that another alternative had to be found. Wallboard wasn’t the answer and mortar-in-place installations were simply too difficult and expensive. 

Finally, a material was developed to replace wallboard for wet-tile installations. It’s known generically as “cement-backer board” or “mortarboard.” Mortarboard can be installed over a waterproof barrier and has the same water-stopping qualities of tile in mortar installation. Mortarboard is very different from the old-fashioned and far-too-flimsy tile-on-wallboard. Now you know why cement-backer board was developed and why it has become so popular. Once the grout starts to leak, the surface below doesn’t fall apart. Backer board was developed to hold together when attacked by moisture, and it does a good job of it. 

Even though mortarboard resists moisture better than does wallboard, it doesn’t smooth the surface. If the studs are crooked, the mortarboard will telescope the problem through. If you want good results, you have to make sure the wall studs are perfectly straight and that the face of each stud perfectly aligns with the face of each adjacent stud before applying the waterproof plastic and the mortarboard. Shimming and planning the studs as needed would be a smart thing to do. 

Each manufacturer will recommend a different fastening method. Follow the manufacturer’s installation instructions to the letter. What you do with one product might not be recommended with another. Once the board is up, joints are taped and filled with joint compound — usually latex-fortified mortar. Latex-fortified mortar is a fancy way of saying mortar mixed with glue. Be sure to leave a 1/8th-inch gap between sheets for expansion. Mortarboard expands and contracts just as wood does. 

Some say that mortarboard is the answer as a base for tile floors. We don’t agree completely. Yes, mortarboard is an alternative to plywood. However, troweled-in-place mortar is still the finest way of doing any tile job.  

With mortarboard, the floor that it will rest on must not vary in height more than 1/8th-inch. Believe it or not, this is a rather stringent tolerance. Most manufacturers recommended that a thin coat of mortar be used to level the floor before the mortarboard is applied. 

We sometimes wonder if our father would have tried tile work if mortarboard had been available then. We think he would have. 

If you are extremely careful with mortarboard, the job can look magnificent — without a lot of work, experience or cost. We have seen mortarboard tile jobs that look better than others where the tile was set in troweled-on mortar. However, a good mortar job is always better than a good mortarboard job. 

 

Tip of the week: Mildew Elimination 

 

We have long been passing along this formula to eliminate mildew. You can use it on any washable surface. All you do is add 1 quart of liquid laundry bleach and 1 cup of powdered laundry detergent – less if concentrated – to 3 quarts of warm water. Scrub the solution onto the mildew-affected area, and be sure to keep it wet until the black mildew turns white (when mildew changes color from black to white, it’s dead). Although this is a relatively safe concoction, to be certain of safety, use eye protection, wear rubber gloves and make sure there is plenty of ventilation.