Here's What Causes Loose Grout—and How to Fix It

Nothing beats walking into a bathroom or kitchen with gleaming, perfect tile bonded with smooth, clean grout. But if your grout is loose, it's not only unsightly—it can be dangerous, leading to slipping hazards and even mold. That's why it's essential to understand what causes loose grout, find out how to spot it, and learn how to repair it.

This guide breaks down some of the most common causes of loose grout and offers telltale signs on how to identify and fix it so you can enjoy the look and feel of that seamless tile.

What Is Grout?

Grout is a mixture of water, cement, and sand that fills the gaps between the tiles throughout your home. It's basically the glue that holds everything together in those areas, so if it's loose, you'll notice it. A homeowner or professional usually mixes these materials together and applies the grout when wet, allowing it to set over a certain period.

Signs of Loose Grout

These telltale signs should help you determine once and for all if you have loose grout.

Loose Tiles

Tiles should never be loose. The grout should firmly anchor them in place, so if you can feel movement in the tile when you step or push on it, that's an indication of loose grout. Loose tiles are a tripping hazard, and can result in additional problems down the road—a few issues now can spread through the whole floor and cause widespread damage over time. Reinstalling the tile with new grout may be necessary, and if it’s a small enough fix you can do it yourself, but consult with a professional first if you are unsure whether you should attempt to fix it on your own.

Mold

Grout should provide a seal between the inside of your tiles and the outside world, so if you're seeing mold develop quickly, that's a definite sign that moisture is seeping through your loose grout and causing the mold.

Cracked Grout Lines

If you can see damage to the grout, such as cracks or deterioration, you should consider having a professional come take a look. It's possible the grout was installed improperly, or that there are issues with substrate deflection (an industry term for the bending of the underlying surface), but either way, you should address it.

What Causes Loose Grout?

There are many reasons why your grout can become loose, ranging from how it’s mixed to how it’s installed to the environment in which it was installed. Here are some of the most common reasons for loose grout.

Structural Failure

If the floor shifts beneath the tile, it could cause the grout to become loose. And while it’s not as common a problem with walls, structural failure is sometimes to blame for loose grout in those areas.

Insufficient Packing

When you install grout, you really need to pack it in there good and tight. If you don't use enough force, the grout may not penetrate as deeply as it needs to, leaving the grout with little overall strength and making it susceptible to loosening later on.

Too Much Water in the Mix

If the installer mixes too much water in the grout, or uses too much water while dressing the joint, the grout may fail.

New Grout Installed on Top of Old

When you install grout, it’s vital that you scrape out as much of the old grout as possible. If you don't, the poor-quality grout underneath will undermine the strength of the new grout you put on top of it.

Moisture Seeping In

Cement is porous, so grout must be sealed before it can be exposed to moisture. If the grout was applied after moisture already seeped into the cement, it could cause the grout to lose its structural integrity.

How to Repair Loose Grout

Even if you’re not a handyperson, it’s not particularly difficult to do a simple re-grouting job. As long as you have the right materials, you can repair the grout in a relatively short amount of time.

To do this job, you'll need the following items:

• Grout float

• Grout or rotary saw

• New grout mix

• Damp towel

Once you have these items, which are available at most hardware stores, take the following steps to repair the grout.

1. Remove the Old Grout

First, remove cracked and damaged grout. A rotary saw is a good way to do this. Vacuum up the excess grout and clean up the area so it's ready for you to lay down the new grout.

2. Mix the New Grout

Follow the manufacturer's instructions on the container for mixing the new grout.

3. Spread the Grout

Using the grout float, spread the new grout evenly over the grout lines. Go slowly and ensure there are no air bubbles.

4. Remove the Excess Grout

Use the edge of the grout float to remove any excess grout so you have clean, smooth lines between the tiles. Then, wait a few minutes so the grout has time to set a little, and then use a damp towel to clean up the area. You can also buff the area afterward.

Should I Use Caulk to Fix Loose Grout?

If you've got problems with your grout, consider using caulking instead in some cases, or even as a supplement. Caulk is made from different materials than grout, and it's more flexible and doesn't dry as hard as grout.

For example, if you have cracks in your grout, a simple fix could be to use some caulking to fill those cracks in. Use a grout or rotary saw to get all the cracked grout out, and then just caulk the cracks in and smooth it over. You'll need to let the caulk cure for 48 hours to ensure it has properly set.

When You Should Hire a Professional

While this can prove a do-it-yourself project, if you have widespread issues with loose grout, problems with mold, don’t own or want to purchase the necessary tools—or you’d rather do something else with your Saturday, consider contacting a grout repair professional near you to come out and take a look. They can do a deep inspection, make some recommendations, and provide you with a quote.

With this knowledge in hand, you can determine whether you want to move forward with hiring a professional, or if you'd like to take a crack at doing the job first yourself.