How to Fix a Leaky Basem*nt Wall From the Inside and Outside (2024)

Fixing a leaky basem*nt wall is critical to maintaining the structural integrity and health of your home’s interior. Beyond simply having a bad smell, water in your basem*nt can lead to mold and structural issues for your foundation that will affect your entire home. Fixing these leaks before they become worse is critical.

Fixing a leaky basem*nt can be done from inside or outside. From the outside, you can patch with a store product or, if the leak is bad, you can dig up the foundation and put a waterproof membrane to the entire wall. From the inside, your options are the same, including using a membrane to simply patching with a product from the store.

In this article, we’ll go over all your options for fixing a leaky basem*nt wall, from simple fixes to major overhauls that will ensure you never have water in your basem*nt again!

What Are the Causes of Leaky Basem*nt Walls

There are likely too many causes to count, but below we’ll go over some of the most common causes of leaky basem*nt walls. There are several different types of foundation, but many of these causes can occur in both poured foundation walls and concrete block basem*nt walls.

1. Cracks in Poured Concrete Wall

One of the most common leaks for homeowners is with a poured basem*nt wall. Some poured walls are poured in sections, and the joints between sections are often prone to leakage.

2. Cove Joint

The cove joint is where the exterior of the basem*nt wall meets the footing. Some masons would use leftover concrete to make a “bead” all around the joint as a means of “waterproofing” the joint. Concrete itself, however, does not waterproof a joint and water often gets into the joints and slides beneath the wall into the basem*nt.

3. Porous Masonry or Concrete

Damp spots on concrete block walls or poured foundation walls are not uncommon, and signs that you need to add waterproofing to either the inside or exterior walls. Damp walls will lead to mold, particularly interior walls covered by framing and insulation. They will also degrade the walls themselves, resulting in shifting that could alter floors, walls, and other parts of your home.

4. Mortar Joints

The mortar joints in your basem*nt walls are the parts between the concrete blocks. Mortar holds them together and is often a space where air pockets or cracks can form due to improper mixing of the mortar or poor application. Either way, it is a favorite haunt for water, and it isn’t uncommon to see water stains running down the mortar to the floor.

5. Seepage Over the Top of Basem*nt Walls

In some instances, you may have a basem*nt wall that tops out close to ground level. That means that the earth comes up to the topmost portion of the block or concrete wall. In these cases, heavy rain or, more likely, snowmelt will seep over the wall and into your basem*nt.

6. Window Wells

Basem*nt windows are a common entry point for water. Often, they are not caulked or sealed properly, and water finds a way in around the window. Other times, the bottom of the window is very close to the ground, and standing water sits too close to the window. If you have window wells, they might not be properly installed and they can back up and allow water into the house.

7. Tie Rod Holes

While not as common in newer builds, older poured foundations had steel rods called tie-rods that went through the walls to hold the steel rods together before pouring. After the pour, they were removed and filled with hydraulic cement. Over time, that cement can fail and allow water into your basem*nt.

Solutions to Fix Leaking Basem*nt Walls

There are many solutions for fixing leaking basem*nt walls. Some work better than others, and some fixes only require small steps, whereas severe leaks require major fixes.

Interior Basem*nt Leak Fixes

Interior basem*nt leak patching can occur using several products that are all readily available at your local home reno store.

• Patching with epoxy. There are many epoxy products you can use to fix leaks. Commonly referred to as epoxy injection, the product comes as a thin or thick paste depending on the size of the patch. It takes a long time to harden but is incredibly strong. It can be used for structural repairs and will fill the entire crack.
• Patching with hydraulic cement. Hydraulic cement is regular cement with gypsum. It hardens when it interacts with water, hence the term “hydraulic”. When you already have water in your basem*nt, hydraulic cement is a great option for filling cracks. It sets very fast, however, so it is not ideal for filling a hole as it will dry before you can fill the entire hole.
• Patching with polyurethane. Patching with polyurethane is also effective but is not used for structural crack repair. It comes as a foam and has flex, so it can get larger or smaller depending on the crack. With a lower compressive strength, polyurethanes are for minor repairs. They dry almost immediately, so you get nearly instant sealing.

Major Interior Basem*nt Leak Repair

For large leaks in your basem*nt walls, you’ll need to install an interior waterproofing system. This repair involves removing all finished parts of your basem*nt walls, down to bare walls. A trench must be dug – or jackhammered – around the basem*nt wall interior perimeter.

Once the trench is dug, a weeping tile pipe is laid and backfilled with gravel. A dimpled, waterproof membrane is placed over the entire wall. Once in place, concrete is poured over the trench with the tile and membrane.

Any water that leaks through the walls will go down the membrane, into the tile and then be deposited out beyond the house by a sump pump placed in a pit where the tile drains into.

Fixing a Leaky Basem*nt Wall from the Outside

There are several different ways to fix a basem*nt wall from the outside. Many of the fixes you can use on interior walls can also be used on exterior basem*nt walls. For instance, epoxy injection and hydraulic cement can be used outside, too. Below is a list of your options if you want to fix a leaky basem*nt wall from the outside.

• Patching products. Hydraulic cement, epoxy, and polyurethane are viable solutions to smaller cracks and holes in an exterior wall. They should only be used for very small leaks, particularly from the outside, as exterior damage is subjected to moisture more frequently than interior cracks and holes.

• Waterproof membrane. Self-adhering bitumen-based membranes come in rolls that stick to foundation walls. When used in conjunction with primer and sealant, they form an impenetrable wall, allowing zero moisture through. Non-adhering membranes attach mechanically and are dimpled to funnel water down to weeping tiles.

• Tar. If you want to keep costs low and rely on a method that’s been used for decades, then choose tar. It rolls on and provides a thin layer of waterproofing. However, it’s easy to miss spots with tar and over time, a crack or hole can form, negating the efficacy of tar.

• Weeping tile. Regardless of your basem*nt wall waterproofing, your home should always have weeping tile. It is a perforated pipe that runs the exterior perimeter of your home’s foundation footing. It leads to either a sump pit inside your home or a french drain – if your home is on a slope. A weeping tile is your first line of defense against water in your basem*nt.

How to Fix Leaking Basem*nt Wall From Inside

The best way to fix a leak from the inside is by using epoxy injection. Epoxy injection is a two-step process.

Adhere epoxy injection ports at even intervals along the crack. Place epoxy paste over the entire crack. This “seals” the epoxy in the crack once the epoxy is injected. Once the paste is dry, slowly inject epoxy into the injection ports, one by one.

Start at the lowest port and fill until the epoxy is seen in the next port. Cap off the lowest port, then continue along the crack in this manner. Epoxy will fill the entire crack, from the interior to exterior, and cures in about 5 hours.

If you have many cracks or a leaking cove joint, a more serious basem*nt waterproofing system is needed – see below.

1. Remove stud walls around the perimeter of the basem*nt – or just in problem areas.

2. Plan your project accordingly, taking into account space for a sump pit and outlet house. Choose a sump pit and pump before you begin, so you know exactly how much space it will take up in the basem*nt.

3. Remove concrete floor 12” to 18” from the base of the exterior walls. Use a jackhammer. The basem*nt slab will be over the top of the footing. Make sure the footing is left intact. Concrete slab pieces should be removed. The trench must be deep enough to see the entire side profile of the footing.

4. Dig a sump pit – 3’ at least. This will be the endpoint of the interior weeping tile. Jackhammer a hole 6” wider in diameter than your new sump pit. Dig down at least 3’ to accommodate the new pit.

5. Lay a bed of gravel then a solid weeper against the footing. A “weeper” is a PVC pipe with small round holes punctuating its entire length.

The pipe will sit flush against the vertical interior face of the footing and connect to the sump pit. Ensure the sump pit connection is below the grade of the rest of the pipe to encourage drainage.

6. Put gravel over the weeping tile. Use ½” or ¾ gravel or pea gravel. Fill the trench but leave a bit of room for the concrete and membrane that will go over the gravel/weeping tile trench.

7. Put dimpled membrane on walls to a height a foot above the ground level and make sure it goes down and over the gravel/weeper. The membrane attaches with manufacturer-specific fasteners at the top of the basem*nt walls.

8. Attach weeping tile to the sump pit. Use a mechanical fitting as indicated by the manufacturer of the pit, such as a pipe clamp. Backfill around the pit with gravel.

9. Pour new concrete over your weeper/membrane and around the sump pit. Use a product that has, at minimum, a 4000 psi compressive strength. Use a bonding adhesive so new concrete bonds to existing concrete.

10. Install sump pump outlet. Choose a spot that has a grade sloping away from the house. Route a rigid pipe through the basem*nt walls or route it up and through a rim joist in your basem*nt.

11. Re-install walls and finish your basem*nt.

How to Fix Leak in Basem*nt Wall From Outside

If you want to fix your leaky basem*nt from the outside, is best to do so with a full-scale exterior excavation. Once done, it will protect your basem*nt walls. Interior waterproofing keeps water out of your living space, but not your walls. Structural problems could occur over time.

Below is a step-by-step overview of how to waterproof exterior basem*nt walls.

1. Excavate foundation. Ideally, you excavate at least 4’ from the walls of your basem*nt. You must dig down to expose the entire footing. You don’t want to further damage your walls with an excavator, so consider hiring a pro.

2. You’ll need to clean your walls before applying the self-adhering membrane. Use a pressure washer on a low setting. Ensure the water has a place to go – either an existing sump pit or pump out any standing water with a utility pump.

3. Apply the primer for the self-adhering membrane. It will come in large buckets and roll on. Some primers require immediate membrane application, and others need to sit for several minutes or longer. Read the directions on the bucket. Roll it on using a roller.

The membrane will need to cover the entire wall to grade level and go over the footing, including the cove joint. Ensure primer covers this area.

4. Install the membrane. This is a two or three-person job as the membrane is very sticky. Ensure the membrane is flat – no bubbles – against the walls. Overlap sheets by at least 1.5”.

5. Apply sealant on all joints. Use manufacturer-specific sealant. For instance, Blueskin membrane has Blueskin sealant, available for purchase in the same aisle as the membrane itself.

6. Install the dimpled membrane. This membrane is not self-adhering and fastens with nails or screws designed for foundation walls. Ensure the dimples face the walls, and use the fasteners as indicated by the product. The membrane will go down to the bottom of the basem*nt walls.

The top of the dimpled membrane will go above grade and be covered by a manufacturer-specific strip that will keep water out.

7. Install the weeping tile. Use a black perforated weeper with a filter sock. It will sit against the vertical face of your exterior footing. Ensure that it connects to a sump pit on the inside of your house – it will go under the footing of your home to connect.

8. Backfill the weeping tile with a foot of pea gravel. Then cover the weeper and pea gravel with landscape fabric. This will ensure all water is diverted to your weeping tile drain and keeps all other dirt and sediment out.

9. Backfill the rest of the excavated area with ½” gravel, up to within a foot of ground level. Top off the excavated area with topsoil, ensuring you have at least ½” of drop per foot of distance away from the house.

How Not to Fix a Leaky Basem*nt Wall

Taking shortcuts to fixing a basem*nt leak is never a good idea – it will simply result in more leaks and result in a greater cost to fix what could’ve been a potentially cheap solution. Here’s what not to do when attempting to fix a leaking basem*nt wall.

• Never apply sealers – epoxy, polyurethane, cement – on dirty walls. If the walls are painted, remove the paint. If the walls have a white, chalky substance on them – efflorescence – then it must be removed, too.
• Never begin a waterproofing project without first checking your exterior water management. That means ensuring gutters are not clogged, downspouts are diverting water at least 6’ away from the house down a slope, and that the grade around your foundation walls is at least a ½” per foot for at least 10’ away from the house.
• Don’t assume you “know” where your basem*nt leak is coming from. Expose the leak, then watch to make sure that is the only place water is entering your basem*nt. You don’t want to patch a crack, then find out two months later there was another crack you missed, and you then have to replace your finished walls all over again.

Tips and Tricks for Keeping Basem*nt Walls Dry

There are many quick fixes for ensuring your basem*nt stays as dry as possible, and most are within the ability of nearly every homeowner. Before you rush to excavate your foundation, try these ideas first to keep your basem*nt dry.

• Keep your gutters clear. Clogged gutters result in water going over the top of your gutters in spots you don’t want it to, which results in water pooling near your house where it wasn’t meant to pool. Gutters failing are a major cause of basem*nt leaks.
• Divert downspouts as far away from your home as possible. Ensure they are delivering water onto a slope away from your house. The water should be at least 8’ or more away from your home.
• Walk around your exterior house walls. Make sure the soil slopes away from the house at all times – a minimum of ½” per foot for 10’ or more. You can build up sections with topsoil and a metal rake. Tamp down the topsoil to create a gradient for surface water to move away from your house.

How Much Does It Cost To Fix A Leaky Basem*nt?

The cost to fix a leaky basem*nt is less than $100 for patching of any kind. If you want an interior drainage system, expect to pay anywhere from $3000 for a small section of the wall to $10,000 for an entire basem*nt interior drain system.

For an exterior drainage system, $20,000 is not uncommon for homes of an average size where a full exterior drain system is installed. If you only do one side of your house, you may be able to get a much lower quote, such as $5,000 or less.

Are Basem*nt Leaks Covered by Insurance?

Basem*nt leaks are not typically covered by homeowner’s insurance, as they consider leaks to be caused by the homeowner’s failure to adequately perform maintenance on the house. However, you can get insurance coverage as an add-on for a fairly low annual or monthly rate. Sewer backup and flood insurance, annually, can range from the low $100s up to nearly $1000.

Conclusion

When it comes to keeping your basem*nt dry, you must perform regular exterior maintenance and checkups to ensure water is always going away from your house. This will solve most, if not all, of your basem*nt wall water issues.

If you still have leaks, consider the larger and more expensive drainage systems. While you will pay much, much more than patching, you’ll also have a piece of mind that your basem*nt walls will never leak again.