What Causes Grout to Crack and How to Prevent It

Posted on June 05, 2013 by

Cracked grout is one of those things that can really ruin a tiled wall or floor. It's especially discouraging if you installed the grout yourself because it means you have to do it all over again. To help you avoid this problem in the future, here's what you need to know about cracked grout and how to avoid it.

Common causes of cracked grout

  • Not enough thinset
    One of the common causes of cracked grout is not applying enough thinset when the tiles are installed. Thinset is the cement-based adhesive that sticks tiles onto surfaces. Without enough thinset, the tile would eventually loosen and the grout would then crack.

  • Improper mixing
    Not mixing the thinset properly would eventually lead to cracked grout. If there's too much water or polymer additive in the mixture, the resulting concoction would be weak. Another possible issue is when the timing of the mixture was incorrectly made, like when water is added to the mixture after the grout starts to set, which would make the grout brittle when it dries.

  • The grout was improperly packed
    Cracking can occur if the grout wasn't packed properly into the joint (i.e. the space between tiles filled with grout). This problem often occurs with wall tiles.

  • The backer board wasn't installed properly
    A backer board is a type of panel material used as a substrate for tiles. It's clearly important since this is the surface onto which the tiles and grout are fitted. There's a certain way to install backer boards: there has to be enough thinset underneath, it has to be screwed on correctly, and the seams need to be taped using alkali-resistant mesh tape. Skipping a step could cause your tiles to shift over time, and the grout to crack.

Other possible reasons

  • There's not enough space between your walls and the tiles. Space is actually necessary because walls often exand due to temperature changes. Without space for expanding, the walls will exert pressure on the tiles, cracking the grout.

  • There are no soft joints between the tiles. As mentioned earlier, joints are the spaces between tiles filed with grout. Soft joints are joints that use caulk or silicone instead of grout. These soft joints are necessary because they allow movement on your tiled wall or floor without cracking the grout or the tiles themselves.

To avoid cracked grout or tiles, you need soft joints for every 20 feet to 25 feet in either direction for indoor tiles and 8 feet to 12 feet in either direction for external installations. So if you're laying tiles in a room larger than 25 feet, you need a soft joint. If you're putting tiles outdoors at an area larger than 12 feet, a soft joint is necessary as well.

How to prevent cracked grout

The trick to avoiding cracked grout is to install it properly. Here are a few tips on how to prevent cracking:

Tip #1: Follow the manufacturer's instructions
Each brand of grout has its own quirks so make sure you follow the manufacturer's instructions to the letter to avoid any problems. The instructions would provide the exact amount of water needed for the quantity you'll be mixing.

Tip #2: Remove lumps in the powdered grout
Before you start mixing the powder, be sure to check for lumps first. These chunks form because of the moisture from the air, particularly from bags that have been previously opened. To take out the lumps, strain the powder through a fine-mesh screen. However, you should still stir the mixture well to remove any chunks you may have missed.

Tip #3: Avoid mixing more than two litres at a time
Grout hardens quickly—usually in a half hour or less. Because of this, you should avoid mixing more than a two litres of grout at a time. Making a larger batch would force you to add water when the grout slakes, which means it wouldn't have the right mix of water and polymer additives anymore, and this would likely lead to cracked grout.

For more tips on better grouting, read our guide.

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