Hairline Cracks in Tile Grout: How to Fix

Grout is one of the most important elements in a tile installation. It fills the spaces between tiles and acts as a barrier that prevents moisture from getting into the spaces between tiles. 

Unfortunately, over time grout can crack and develop hairline cracks that are difficult to see at first. They become bigger over time though and can be harder to fix once they expand. 

 As grout begins to deteriorate it cannot perform its function as effectively and moisture penetrates the space between tiles causing other problems. This can result in water damage or even mold!

Fortunately, there are a few things you can do to prevent grout from cracking. If you have already discovered hairline cracks in your grout, there are several ways to repair them so they are almost unnoticeable. Read on to learn how you can get rid of these unsightly cracks.

What Causes Hairline Cracks in Grout?

Grout is a porous material. That means that it has microscopic pores that allow moisture to pass through it. Unfortunately, grout is also very alkaline-sensitive. 

Repeated exposure to strong alkaline cleaning products can damage the grout, causing it to break down and develop hairline cracks. 

The best way to prevent grout from cracking is to use non-alkaline cleaning products. 

It is also possible that the grout wasn’t installed properly or that a nearby material is expanding and cracking the grout.

Grout also breaks down over time. 

Repairing Hairline Cracks in Grout

If your grout shows signs of cracking, you should take immediate action to prevent the problem from getting worse. 

First, determine what caused the grout to crack. If the problem is caused by low pH cleaners, you can fix the problem with an acid-based grout sealer. 

If the problem is caused by high pH cleaners, you can use a grout stabilizer. 

Once you have identified the problem, you can use a grout repair product to fix the cracks.

 The best grout repair product for hairline cracks is an epoxy grout repair kit. You can also use a grout repair kit that contains a silicone-based sealer.

Before you use these, you should use a brush to clean the area around the cracks.

Using silicone Epoxy to Repair Grout

Epoxy-based grout repair kits are very effective at repairing hairline cracks in the grout. To use this type of repair product, clean and scrape off any loose grout and debris. 

Once this is done you can add plastic bags in the tub to make sure that the epoxy won’t damage your shower tub.

You often have to mix two parts of epoxy. Check the manual as the composition has to be mixed correctly. Wear gloves and protective glasses while you do this. Use a squeegee to remove the excess solvent. 

Apply an epoxy grout repair compound to the hairline crack. Smooth and level the crack with a plastic putty knife. Let the repair compound cure for 24 hours. After it has cured, apply a grout sealer to prevent the epoxy from rubbing off.

Expoxy shouldn’t go in the drain. Throw it away in the right way (see the manual of the epoxy that you have bought).

Using Resin to Repair Grout

Like epoxy, a resin-based grout repair kit will work on hairline cracks in the grout. Follow the same steps as outlined above. The only difference is that you’ll need to apply a resin-based grout sealer after the repair compound has dried. 

Make sure that you get clear resin so that you can hide the repair as much as possible.

Resin-based kits are ideal for repairing fiber-mixed tiles, especially ones with a high water absorption rate. Resin-based grout sealers are highly resistant to moisture penetration and will last longer than epoxy-based sealers.

Regrouting the shower

If the previous methods don’t work, you can opt for regrouting the shower. Removing old grout is not always easy and can require quite a lot of work. With the right tools, this can be done in a few hours.

 Once this is done though, you can add new grout again and your shower will look brand new! This will last a lot longer than just repairing the grout.

It is essential that you have found out why the grout has cracked before you do this. Otherwise, the problem can reoccur quite soon after you have regrouted the shower. This is a shame of the hard work that you have put into this. 

Now that you know what to expect, let’s get started with the regrout.

– Start with a clean surface. If there’s dirt or grime on your surface, that will complicate things later. Instead, start with a clean surface to ensure that your regrout is a success.

Once the shower has been cleaned, we can add plastic bags or old towels on the floor. This will make sure that grout doesn’t stick to the shower pan. Shower pans are white and dirt can easily leave spots.

 Before we start, we have to make sure that the shower is not damaged. Inspect the shower tiles. Make sure that there are no broken tiles.

The next step is to remove the old grout from the wall. If there’s any grout left on the tiles, you’ll need to remove it before regrouting. A grout scraper, putty knife or multitool makes this quick and easy. You break the grout by scraping it. This can release a lot of dust so have a brush, wet wipe, and vacuum handy.

Mix the grout and have it in a bucket. Check the color of the grout so that it matches your tiles. Mudding is done by stroking the sealant over the grout.  Grout often has to be mixed up by yourself and this is quite easy to do as you just have to add water and mix it. Now we can finally regrout the shower.  This is generally done with a trowel. It can be quite challenging to fill a grout completely. You shouldn’t make a turning movement. This is quite similar to waving to someone.

You can scrape excess grout from tiles with a scraper. You can also use a sponge to clean it further. Finally, go over the grouts with a wipe once it has settled. Check the manual of your grout filler for more details on this.

The grout should rest for at least 24 hours before you use the shower again.


Hairline cracks in grout can be repaired using one of the two methods discussed in this article. These methods are epoxy grout repair or resin grout repair kits. These kits are cheap and it is easy to apply them.

It is still essential to find out why the grout is cracking. It is possible that you are using cleaning products that are too aggressive, you don’t ventilate the bathroom enough, or there is a problem with nearby materials.

Once you have found the root cause of the problem, you can use a repair kit or simply regrout the wall. The last option is more work but it delivers the best results.