Cracked Floor Tile

If you have ceramic or stone tile installed directly to your concrete floor, you may have noticed cracked tile. There can be a number of reasons for this, including inadequate bonding, lack of expansion joints, use of an inferior grade of thinset, and cracking of the substrate. For the purposes of this article, I’ll address only the last factor: cracking of the substrate.

Many concrete finishers will tell you that it’s not a matter of whether or not the concrete will crack, but when it will crack. While there are a number of reasons for the concrete to crack, it’s almost impossible to determine when and where it will crack. Cracking sometimes occurs at the weakest point of the slab. For instance, if there is an inset porch in a floor plan, there may be one or two weak points in the slab. The slab is narrower at this area, hence the weak point. However, it’s possible for concrete to crack at any place or time, even several years after the slab has cured.

There are other contributing factors, such as:

• improper mix of the concrete recipe
• excessive heat or cold at the time of the pour
• excessive heat or cold during the curing times
• improper preparation of the base on which the concrete is poured

Given all these factors, you can see that it’s almost impossible to account for every variable when predicting when or where concrete will crack.

When tile is installed directly to the concrete with thinset it is referred to as “direct bonding.” Direct bonding is an acceptable method of tile installation and is widely used in many applications, however, the integrity of the tile installation is completely dependent upon the integrity of the concrete slab. In short, if the concrete cracks, the tile is very likely to crack as well.

Extreme weather changes can also cause a concrete slab to expand and contract significantly, so what started out as a hairline crack can expand to a much larger crack, which could then contract to it’s original size later. Tiles that span this crack will not expand and contract at the same rate as the slab, so when the tile is “stretched” to its limit, it will ultimately break directly above the crack in the slab.

A cracked tile is a relatively easy fix, but outside factors can create other problems. If your tile was installed several years ago, you may find that it is no longer manufactured, making it difficult or impossible to obtain replacement tile. For this situation, many times the only remedy is to remove all the tile and install a different tile. Obviously this is a very expensive and messy undertaking. If you have replacement tile, you can remove the cracked tile and install new ones. However, if you install the new tile using the same method used in the original installation, it’s very possible that your new tile will crack as well. Removing the grout around the cracked tile is a necessity, and often when the tile is replaced and re-grouted, the new grout will not match the old grout.

A number of products on the market are available to prevent cracked tile. They fall into two basic groups. Each product has its own positive and negative attributes, and here I’ll try to illustrate a few of them.

Crack Isolation Thinset. A popular crack-isolation thinset is manufactured by Laticrete and is called 125 Crack Suppression Adhesive. Laticrete 125 is used just like standard thinset, but it remains flexible forever, therefore allowing the slab to move without damaging the tile. While 125 is a superior crack-isolation product, it is very expensive and a little messy. Laticrete 125 costs about $2 per foot (as of the date of this article), so in most cases it is not a product that you would want to use over the entire installation. In my opinion it is the best product for installing individual tiles over an existing crack. Laticrete 125 can be mixed to any amount so you can use if for one tile or several.

Crack Isolation Membrane. If I were concerned that cracks might occur in the slab in the future, I would use a crack isolation membrane. There are a number of membranes on the market, including Custom Redgard or Custom Fracture Free. A membrane is simply painted on the slab with a brush or roller to the required thickness. The membrane effectively separates the tile from the slab allowing independent movement. Standard thinset is used to bond the tile to the membrane. Most crack-isolation products will allow movement of up to 1/8″ in the slab while preserving the integrity of the tile.

While there is no guarantee that any of these products will absolutely prevent your tile from cracking, they are certainly your best bet. It’s also important to note that the cracks I refer to in this article are lateral, or horizontal cracks. Cracks that have vertical displacement (one side of the crack is higher than the other) will still cause damage to your tile. Currently, there are no products available that will suppress cracks that have vertical displacement.

Kevin Trevathan is an expert in ceramic and stone tile installations. He owns Trevathan Floorcovering in Pea Ridge, Arkansas. Visit his website for more articles on tile and hardwood flooring: www.TrevathanFloors.com