Why are my Tiles Cracking?

It’s so frustrating – whether it’s new tile or old: unsightly cracks. Wait a minute – I thought tile was supposed to be durable! Let’s explore some reasons this might happen.

Estimated reading time: 5 minutes

What causes Tiles to Crack?

There are only two things that really cause damage to tiles – movement and forceful impact. Every good tile installation will plan for and address expected movement and some amount of impact resistance. Depending on the type of movement, the patterns of damage don’t look the same, however. With a little sleuthing, you may be able to figure out the exact cause of your tile cracks.

Installation Mistakes and Practices

What we have often found is that cracks are often the result of a poor installation, whether through carelessness or a lack of understanding about the nature of a tiled surface. Installers experienced in the other trades can sometimes bring with them misconceptions about proper tile installation.

A well-bonded tile is one that has a consistent coat of mortar across the back that not only bonds it to the floor/wall, but supports it as well. There are a few problematic methods that crop up commonly, including spot bonding, troweling too little mortar with too small a trowel, and randomly troweling patterns. The following video shows a number of these problems and why they are problematic.

Setting tile is more than this, however. There are constantly new products, methods, and best practices to keep up with. A certain amount reading is required, and we see a lot of newer products being installed improperly as a result of not taking the time to read the datasheets or instructions. Waterproofing products in particular seem to be something that flummoxes many a contractor. Newer grouts also have different mixing times and speeds than those of yesteryear. Product failures as a result are not uncommon in the industry.

Deflection cracks: Movement Up/Down

Deflection is a fancy word for the amount of expected up and down movement in a floor. All floors will bend somewhat when they carry weight. The deflection measurement is a measurement of how much a floor system will bend under a given weight. You’ll see L/360 and L/720 thrown around in the tile world – those are measurements indicating a maximum allowable “bend” of 1-inch over 360-feet (or 720-feet).

If you plan to install ceramic/porcelain tile, your floor system must be build to L/360 or less (keep in mind, the high the L/number, the less the deflection). For any natural stone tile, you’ll need your floor system to be built to L/720 or less. If your current floor is not going to work for the product you’ve chosen, there are ways of increasing its rigidity/strength, but it will be more work to make that happen.

When your tile contractor gives you a bid, you’ll want to make sure that they take measurements for the joist structure in your home. While calculating deflection is not difficult, many skip this step and and up with cracked tiles as a result of the floor ‘bouncing’ too much.

Expansion/Contraction: Movement Side-to-Side

A photo of a cracked tile as a result of leaving no expansion gap. You can see that the tile is tight against the shower pan, and has developed a crack as a result.

All floors need room to expand and contract for temperature and humidity changes. Your tile will need a perimeter joint between the outer edge and the wall. Here’s something you probably don’t want to happen:

This is a worst-case scenario: the tile here is popping off the floor because of a lack of expansion joints in the tile assembly combined with insufficient mortar adhesion.

What you see in the video above is that the floor assembly has expanded, without actually having the room to expand. The tile wasn’t well-adhered to the substrate, so with all the sideways compression, it yielded and “tented.”

Regular expansion joints are similar in concept – every so often, a movement joint must be installed to allow for expansion and contraction. For interiors, these are usually every 25 feet, unless they are exposed to water or sunlight, where that measurement would drop to every 12 feet.

We sometimes find that certain glass tiles can be problematic in showers – glass tends to expand and contract more that other materials from heat of the shower water. It sometimes causes small fractures across an entire wall. There are glass tiles rated for shower wall use, but each type of tile must be verified before installation.

Forceful Impact

Let’s not forget that tile isn’t bulletproof. Dropping things, especially sharp objects can cause an impact that can gouge or break a tile. The difference is that these usually take the form of chips or defects on the surface of the tile. The mortar should be holding the back of the tile solid, and the damage won’t travel all the way through.

My Tiles have started cracking – what can I do to stop it?

Unfortunately, there’s not much you can do, unless you want to avoid that section of floor. All of the things causing the tiles to crack are already done, so there’s very little to remedy the situation. If the underlying structure isn’t supporting the tile well enough, the only thing to do is live with it until you’re able to remove the tile and start over.

What if they are only hairline cracks? Am I still in trouble?

Not always – it’s probably best to wait and see. There are a number of tiles with cracked glaze, manufactured deliberately to look that way. If the cracks aren’t traveling or spreading apart, there’s a good chance they will stay that way.