Why Does Bathroom Grout Crack?

image of cracked grout in bathroom

As a homeowner, you will likely have to deal with cracked grout in your bathroom at one point or another.

It can be frustrating to see your tiles falling apart.

However, there are many logical causes for these types of problems. When this happens, you should call a qualified professional to assess and repair the damage. These issues tend to escalate so it is important to address them as soon as possible. There may be issues as hand that require the help of a bathroom plumber Palmer PA. In this article, we will discuss some of the possible causes of cracked bathroom grout.

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What Causes Cracked Bathroom Grout?

Keep reading to find the causes for cracked bathroom grout.

Cement Hydration

image of tile adhesive cement in bathroom

As part of the curing process, cement hydration is vital to creating strong grout. More specifically, if you add water after cement hydration has already begun, the water will weaken the grout’s structure and ultimately, cause it to crack.

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Loose Subfloor

If your bathroom has a loose sub-floor or a structurally unsound floor, such as a bouncy floor, the grout is likely to crack. For instance, if you install tiles directly onto a typical wooden sub-floor, the grout is likely to crack because the sub-floor is unlikely to be strong enough to protect the tile and the grout.

If you have such a sub-floor, you should hire a professional…

to install tiles in your bathroom. In such a case, a professional would first install a concrete board on top of the wood sub-floor in order to make the floor structurally sound.

Foundation Settling

image of lifted tile due to foundation settling in bathroom

The foundation of a building/structure typically sinks down into the ground over time due to various factors including weather and vibrations caused by human activities such as construction. It is called “sinking” and occurs when the foundation is settling. This can cause the grout in your washroom to crack. However, this does not necessarily mean that the tiles held together by the grout would crack too. Grout is more flexible than tiles, meaning it is more susceptible to cracking under such conditions.

Insufficient Thinset

When installing tiles, it is important to use sufficient amounts of thinset (the adhesive applied over the mortar during the installation of tiles) to prevent the grout from cracking. This is because, as the thinset sets, it typically hardens, contracts, and pulls tiles tight to the mortar. For this reason, if an insufficient amount of thinset is used, the thinset is likely to pull away from the tiles, leaving air spaces under the tiles. When this happens, the grout is likely to crack.

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Movement Joints

A movement joint is basically anywhere a tile surface changes plane, such as an interior corner, or meets an abutting surface, for example, against a hardwood floor or wall. This is according to the Tile Council of North America (TCNA). Additionally, the TCNA says that the entire surface of a bathroom installation is a movement joint. For this reason, it should have room to accommodate movement. This means that, if your tiler applies grout to a movement joint, the grout is likely to crack. However, such areas should also be sealed to prevent moisture, induced damage, and improve aesthetics. Fortunately, your professional can use a more flexible material, such as 100-percent silicone, to seal such joints.

Weak Grout Structure

Improper mixing of the grout is likely to cause the grout to crack. More specifically, too much polymer additive or water in the grout mix is will likely lead to this problem due to excessive evaporation.



Some of the possible causes of cracked grout in the bathroom include:

  • weak grout structure
  • movement joints
  • foundation settling
  • insufficient thinset
  • loose sub-floor

Be sure to address these issues…

as soon as you notice them. The longer that you wait, the more of a headache that it will become.


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