Blog › February 17, 2025
How to Stop a Foundation Crack from Leaking
Not all foundation crack repairs are equal. Here is what actually works to stop water from coming through a crack, why surface patching keeps failing, and when to call a professional.
First: Understand the Type of Crack
Foundation cracks are not all the same, and the right repair depends on what type of crack you have.
- Vertical cracks are the most common in poured concrete walls. They form from shrinkage as concrete cures or from settling. They are typically not structural but are a direct path for water.
- Diagonal cracks typically run at 45-degree angles from corners — often window corners or door openings. They may indicate differential settling. They can leak significantly.
- Horizontal cracks are the most concerning and indicate lateral pressure from soil against the wall. These require structural evaluation, not just waterproofing.
- Stair-step cracks in block foundations follow the mortar joints and indicate settling or movement. The entire mortar joint network may be compromised in a wet block wall.
Why Hydraulic Cement and Patching Fails
The most common DIY and budget contractor approach to a leaking crack is to pack it with hydraulic cement, apply a coating of waterproof paint, and call it done. This approach fails consistently, and here is why: hydraulic cement and coatings applied to the interior surface of the wall are holding back water pressure from the outside. When the soil saturates again and pressure builds, that patch gets pushed, cracked, or simply bypassed as water finds another path.
We see this on virtually every home that has had "repairs" done by previous owners. Multiple layers of paint, old hydraulic cement patches, and new leaks forming right next to the patches. The underlying pressure was never addressed.
What Actually Works: Polyurethane Injection
The professional standard for leaking poured concrete cracks is polyurethane or epoxy injection. This involves drilling a series of small injection ports into the crack, then pumping a low-viscosity resin under pressure through the full depth of the wall. The resin fills the entire crack from the interior surface to the exterior face of the foundation, and cures into a flexible, waterproof seal that bonds to the concrete on both sides.
Because the seal penetrates the full depth of the wall, it is not fighting water pressure at the surface — it creates a barrier through the wall itself. The flexibility of cured polyurethane allows the seal to accommodate minor foundation movement without re-cracking.
When Injection Alone Is Not Enough
Injection seals the crack that exists today. If the underlying drainage situation around the foundation is not addressed, the soil will continue to saturate, the foundation wall continues to experience hydrostatic pressure, and new cracks may develop nearby over time. For homes with significant cracking, active water intrusion, or a history of repeat leaks, interior drain tile that manages the water load on the foundation is the more complete long-term solution.
An injection repair on a single isolated crack in an otherwise sound foundation with reasonable drainage is typically sufficient. An injection on one crack in a wall with four other cracks and 3 inches of standing soil water against it is a partial solution at best.
Horizontal Cracks: A Different Situation
If your crack is running horizontally across a basement wall, this is a different conversation. Horizontal cracks indicate lateral soil pressure that is bowing or bending the wall — this is a structural issue, not just a waterproofing issue. Sealing a horizontally cracked wall does not address the structural movement. This type of crack needs structural assessment and potentially repair with wall anchors or carbon fiber straps before waterproofing is addressed.
Getting the Right Repair
If you have a leaking crack in your Utah Valley basement, we offer free inspections throughout the area — Provo, Orem, Lehi, American Fork, Spanish Fork, Springville, and all surrounding communities. We will identify the crack type, assess the overall drainage situation, and give you an honest recommendation for the right repair. Call (385) 448-5185 or request an estimate online.
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