Beginner’s Guide To Detecting And Fixing Slab Leaks

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Slab leaks can be extremely dangerous. If left unattended, they can cause serious damage to your home or business.

A slab leak is a common problem that can occur when water gets into a concrete floor.

The water can then seep through cracks in the concrete and create a wet area around the perimeter of the room. This can cause mold (see also ‘Is White Mold Dangerous?‘) growth, rot, and other problems.

To prevent slab leaks, you should check your floors regularly. Once you notice a wet spot, call a professional immediately. They can repair the issue before it becomes too big.

In this article, we have put together everything you need to know about slab leaks in your home – including how to detect them and the best way to fix them.

Guide To Detecting And Fixing Slab Leaks

What Are Slab Leaks?

Slabs are made up of several layers of concrete. These include:

  • A base layer of cement paste (the stuff that makes up concrete)
  • An intermediate layer of sand and gravel
  • And an outer layer of aggregate (gravel and stone).

When water enters these layers, it causes the concrete to expand and contract. As a result, the concrete will crack and break apart over time.

When this happens, the water can get trapped between the cracked concrete and move along the surface of the floor.

This is why slab leaks happen, and the consequences can be expensive.

Why Are Slab Leaks An Issue?

Slab leaks can cause a major headache to homeowners and can be responsible for more extensive damage to your home, including :


If too much water is allowed to enter the home via slab leaks, then you are at increased risk of flooding. Flooding not only causes significant structural damage to the house, but it can also lead to mold growth.

Water Damage

If water gets inside the walls, then it can cause considerable damage to your property. Water damage can range from mildew to severe rot.

Mold Growth

Mold grows best in moist environments, so if water enters the wall, then it can easily grow and spread throughout the entire structure.

Not only does this make the home look unsightly, but it can also pose health risks to those who live in the home.


Over time, excess moisture can lead to decay within the walls. Decay is caused by bacteria, which thrive in damp conditions.

If you notice any signs of decay, then you should contact a professional immediately, as this can result in more serious structural damage.

Damage To Foundations

One of the most common issues associated with slab leaks is that they can affect the foundations of your home. When water enters the foundation, it can weaken the soil underneath the building.

As a result, cracks can appear in the ground, and this can ultimately lead to further problems down the line.

Damage To Floors

The floor of your home is one of the most vulnerable areas when it comes to slab leaks.

The reason is that floors are usually made up of wood, which means that they can easily become damaged when exposed to excessive amounts of water.

In addition, the floor itself can also begin to rot over time, which can cause even more damage.

Structural Issues

Slab leaks can have a number of negative effects on the overall structure of your home.

For example, if water enters the walls, then there is a high likelihood that it will eventually seep through the ceiling. This can cause damage to the roof, which could potentially lead to leakage.

In some cases, slab leaks can also cause damage to the plumbing system, which can lead to costly repairs.

What Causes Slab Leaks?

As we have mentioned, slab leaks are caused by unwanted water being able to enter the concrete, and this can occur from many different sources, such as:

Rainwater Entering Through Cracks In The Foundation

One of the most common causes of slab leaks is when rainwater is allowed to enter the structure through a crack in the foundation, which may be caused by poor drainage.

If you live in an area with heavy rainfall, it’s important to make sure that your foundation has good drainage (see also ‘ Retaining Wall Drainage: How To Drain Water Properly’ ). 

You can do this by installing gutters (see also ‘How To Install Seamless Gutters‘) on all sides of your house. Make sure that there are no clogs in the gutter.

If you don’t have gutters, consider using a sump pump. It will help keep water away from your foundation.

A sump pump (see also ‘Sump Pump Repair: A Complete Guide‘) is also useful if you have a basement because it helps drain any water that does manage to enter the basement.

It works like a giant vacuum cleaner, removing any unwanted water from the space.

Faulty Plumbing

Another reason for slab leaks is when water enters the floor due to faulty plumbing.

Check your pipes, faucets, toilets, and drains for any signs of leakage. Repair any issues quickly so that you won’t end up with a major problem.

Drainage Problems

You may find that you have a slab leak even though you haven’t experienced any flooding. This could mean that there is something wrong with your drainage system.

For example, if your driveway slopes towards your house, this could allow water to flow downhill toward your home.

You can solve this problem by making sure that your driveway slopes away from your house.

Another option would be to install a French drain. This type of drain uses rocks or gravel to channel water away from your home.

Dripping Pipes

Dripping pipes can be another cause of slab leaks. If you hear dripping sounds coming from your walls, ceiling, or other areas, then you might have a leaking pipe somewhere.

The first thing you should do is turn off all power to the affected area. 

Then, use a flashlight to inspect the area where the sound is coming from. Look for cracks, holes, or anything else that could be causing the noise.

Sewer Backup

A sewer backup elsewhere can be a contributor towards slab leaks. Sewers are designed to carry waste away from your home.

However, sometimes they back up into your home due to blockages or overflows.

To prevent this from happening, make sure that your toilet isn’t overflowing. Also, check around your property for possible blockages.

Check Your Roof

Roof leaks can contribute to slab leaks. If you notice any wet spots near your roof, then you need to fix them immediately.

The best way to do this is to contact a professional contractor who specializes in waterproofing roofs. They can seal any leaks and ensure that your roof stays dry.


Slab leaks can be caused by floods, as a high volume of water can make its way into the slabs.

When this happens, you’ll want to call a flood damage repair company as soon as possible. These companies specialize in repairing flooded homes.

They’ll remove any debris and clean out any standing water.

Afterward, they’ll apply a protective coating to your home’s exterior. This coating prevents moisture from getting inside your home.

How Can You Detect A Slab Leak?

How Can You Detect A Slab Leak?

If you suspect that you have a slab crack, you can easily detect one. Simply look at the bottom of your concrete slab.

You should see a line running across the entire surface. If you see any cracks, then you need to get them repaired right away.

If you’re not sure whether you’ve got a slab leak, then you can try using some of these tips:

Listen For Water Sounds

Water will often drip onto a concrete slab. If you hear a steady drip, then it means that there is a leak somewhere nearby.

Use A Flashlight

Shine a flashlight on the ground near your foundation. If you see any light shining through the cracks, then it means that water has made its way into the slab.

Check Around Your Home

Look around your home for signs of a slab leak. If you spot any wet spots, then you know that there is a leak nearby.

Inspect Your Foundation

Look at your foundation. If you find any cracks, then you probably have a leak.

Call A Professional Contractor

Call a professional contractor if you think that you have a slab leak. They can help you identify what kind of repairs you need to make.

In these cases, your plumber will quickly become your new best friend and are best placed to solve and fix the problem.

Fixing A Slab Leak Yourself

If you want to repair a slab leak yourself, you should always use caution. You never know how much damage you could cause by using too much force.

Always wear safety goggles and gloves while working on the job. Also, make sure that you clean up any spills immediately.

There are two main ways to fix a slab leak yourself. The first way is to simply drill through the slab and patch the leak.

While this is a quick and easy fix, it’s not recommended because it can lead to further problems down the road.

The second way is to call a professional who specializes in slab repairs. They’ll be able to tell you exactly what needs to be done in order to fix your leak.

In most cases, calling in the professionals is the best course of action – they can repair your slab leak quickly and easily, with minimal risk of causing further long-term damage.

How Plumbers Approach Slab Leak Repair

When it comes to repairing a slab leak, many plumbers will have a number of tricks up their sleeves, and these can include :

Draining The Water Out

The most common method of fixing a slab leak involves draining the water out of the slab. Once the water is gone, the plumber will seal the cracks and holes with epoxy resin.

Sealing Cracks

Another popular technique involves sealing the cracks and holes in order to stop the leakage. Epoxy resin is used to fill the cracks and holes, and once cured, it forms a hard and durable seal.

Patching Up Cracks

Sometimes, even after all of the above techniques have been tried, a slab leak still persists. In such instances, a patch may be required.

Patches come in different shapes and sizes. Some of the more common ones include:

  • Concrete patches
  • Fiberglass patches
  • Rubber patches
  • Sheet metal patches
  • Cement patches

All of these types of patches can be used to stop a slab leak, but each type has its own advantages and disadvantages.

For example, cement patches are very effective at stopping leaks, but they don’t last long.

On the other hand, fiberglass patches are excellent at holding onto the concrete, but they aren’t able to withstand extreme temperatures.

In terms of repairing a slab leak, there isn’t just one single solution. Instead, there are several different options available. These include:

Drainage Systems

A drainage system is an ideal option when it comes to repairing a leaky slab. This involves installing a sump pump or drain pipe to remove excess water from the area.


Grouting is another great option for repairing a slab leak. It involves pouring grout into the crack or hole to create a solid seal.

Resin Pouring

Resin pouring is also a good option for repairing a slab. However, unlike grouting, this process requires no tools.

All you need to do is pour the resin into the crack or hole, wait until it sets, and then scrape off the hardened material.


Sealants are yet another option for repairing a slab, and they’re often used alongside other methods.

Sealants can either be applied directly on top of the cracked concrete, or they can be mixed with water and poured into the crack.

Final Thoughts

Slab leaks can be a real headache for homeowners and have the potential to cause a great deal of expensive, destructive damage if left unchecked.

Learning to recognize the signs of a potential slab leak will allow you to take swift action, and either attempt a repair yourself, or leave this to the pros, and reduce the potential damage that is caused to your home.

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Get a free estimate online from top local home service pros in your area.


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