Loo Academy

Hairline Cracks in Grout: Causes & How to Fix Them

Harline cracks in grout are tiny, usually unnoticed little problems. These small cracks are primarily cosmetic issues but can grow into large problems if left untreated over time.

These minuscule cracks can take away from the otherwise pristine look of your bathroom. While it will take some close inspection to see these cracks, they will grow larger and become quite noticeable with time.

As these cracks grow, issues like mold and water damage can grow with them. This article will cover the causes of hairline grout cracks and how to fix them. Tips on preventing hairline cracks in grout are also included.

Let’s get started.

hairline cracks grout
Source: Houzz

Are Hairline Cracks in Grout Normal?

Hairline cracks are caused by many things, from the spacing of your tile to how well you mixed and installed your grout. And while these cracks are not part of a normal proper installation, they are very common.

Hairline cracks are by no means an emergency and do not require your immediate attention. But you should deal with these cracks as soon as possible to prevent more troublesome issues.

The Causes of Hairline Cracks in Grout

Grout Mixture or Installation

When your grout was initially installed, the mixture of water to grout played a pivotal role in the quality of the grout and its lifespan. Giving your grout the time it needs to dry will also prevent cracks and lengthen the lifespan of your grout. Cracks caused by an overly wet mixture or a lack of curing are usually round, patchy, and expand quickly.


With bathrooms seeing the most humidity in your home due to showers and baths, humidity can become a common cause of hairline cracks in your grout. Humidity and moisture can seep into your walls, causing wood and drywall to expand, leaving you with cracks.

Tile Placement

If you don’t use enough adhesive when installing your tile to the wall, your tiles can become loose and crack your grout. These cracks are usually quite long, running the length of your loose tile.

Old Grout

Grout has a lifespan between 15 to 20 years. Your installation and environmental conditions like humidity play a part in determining how long your grout lasts. When grout grows past its prime, cracks can quickly form. You will also notice your grout will crumble, fall out, and become brittle.

How to Fix Hairline Cracks in Shower Grout

Patching Cracked Grout

If your grout still has a long life ahead of it and your cracks are not severe, then patching your grout is the best option.

It’s essential to determine whether you have a crack or a scratch. If you see a crack but do not feel it, the crack has not penetrated your sealant, meaning no patch is needed unless you want to patch it purely for cosmetic reasons.

You can mix up a fresh batch of grout and apply it to your troubled areas. Patching your grout only works in some situations, and if your grout is too damaged or too old, your only other option will be to replace the grout.

Replacing Cracked Grout

If your cracks are significant and widespread or your grout is past its expiration date, then a simple patch won’t do the trick; you’ll have to remove and replace it.

Replacing your grout might be the most expensive and time-consuming solution on this list, but it’s also the most effective. By replacing your grout, you can ensure it’s mixed and cures properly.

Ideally, replacing your grout will give you crack-free grout for 15 or 20 years. But due to the time required and the cost, you should not replace your grout when a patch would solve your issue.

Reducing Humidity

Humidity will always be one of the grout’s worst enemies. So the less moisture and humidity in your bathroom, the less cracked grout you’ll have.

Drying your tiled walls with a towel after you shower or bathe can go a long way in reducing moisture.

A less labor-intensive method is buying a dehumidifier and turning it on for an hour or two after you shower or bathe. Though reducing humidity does not fix cracks, it can prevent cracks from happening or keep cracks from expanding.

Replacing Tiles

If loose tiles are the cause of your grout cracks, you can replace loose tiles to resolve the situation.

Removing tiles requires delicate precision so that you do not damage the rest of your wall. But once the offending tiles are removed, the hard part is over.

Make sure you use enough adhesive when applying your new tiles to the wall, which was the initial cause of your cracked grout. Once the new tiles are in with a fresh layer of grout, you’ll have gotten rid of the cracks and their cause.

How to Prevent Hairline Cracks in Grout

Install Your Grout Properly

The easiest way to prevent grout cracks is to be meticulous when installing your grout. Mix your grout as precisely as possible and give it all the time it needs to dry thoroughly.

Fight Moisture and Humidity

As previously mentioned, reduce moisture and humidity whenever possible, whether that means using towels, fans, or a dehumidifier.

Use Sealant

Using a sealant is not just wise for waterproofing, but sealant acts as a barrier preventing water from entering any preexisting cracks while strengthening your grout.

Be Aware of Your Grouts Age

If you know how old your grout is, you are better informed as to whether it should be patched or replaced. You can replace your grout before it gets too old, preventing cracks and other damage.


Can hairline cracks in grout cause leaks?

Hairline cracks are tiny, but water will seep through them. Over time more water can seep through these cracks, which will eventually expand the cracks and cause water damage.

Can I caulk over cracked grout?

Caulking over cracked grout is not an ideal option. You can use certain waterproof acrylic caulk in the shower, but at best, it’s only a temporary solution until you can replace the grout.

James B. Parker

At a young age, James' father taught him carpentry, and he was pretty much destined for a career in the construction industry. He worked as a professional remodeling contractor for some of the most prominent construction companies for several years, before deciding to pursue his passion for writing.

A vast amount of construction experience allows James to provide practical advice for those considering a bathroom remodel.