What is a foundation crack and why does it leak?
Poured concrete foundations crack. It is normal. Concrete shrinks as it cures, the ground settles around the foundation, freeze-thaw cycles flex the wall, and over years that movement opens hairline gaps that grow with time. A dry crack is harmless. A wet crack is your basement's primary entry point for water.
The good news: most cracks in poured concrete foundations are non-structural and can be permanently sealed in a single 1-2 hour visit. You don't need a $15,000 system. You need an injection.
Types of foundation cracks
Vertical cracks
Most common. Usually run from the top of the foundation wall down toward the footing. Almost always non-structural - the result of normal concrete shrinkage. Polyurethane injection fix.
Diagonal cracks
Run at an angle, often from a corner of a window or door opening. Can indicate either normal settlement or differential settlement (one side of the house dropping more than the other). Often non-structural but worth a closer look. Polyurethane usually, epoxy if structural concerns.
Horizontal cracks
The serious one. A horizontal crack across a foundation wall often indicates the wall is bowing inward from soil pressure. This is structural. Injection alone usually isn't enough - we may recommend exterior excavation, wall pinning, or carbon fibre reinforcement. We won't quote a $500 injection on a wall that needs $10,000 of structural work.
Stair-step cracks
Found in block foundations (concrete masonry units). Follow the mortar joints in a stair pattern. Treatment depends on whether the cracks are structural and on whether parging is intact. Often need a different approach than poured concrete cracks.
Tie-rod hole leaks
Not technically cracks - they are the small round holes left from the steel tie-rods used during the original concrete pour. Original tar plugs fail at 30+ years and the holes start dripping. Quick polyurethane fix at $200-$300 each.
The injection process, step by step
- Inspection. We look at the crack from inside, check the corresponding outside grade, and confirm whether injection is the right fix. If it is structural, we tell you.
- Surface prep. We clean the crack face of paint, dust, and old patch material so the surface seal will hold.
- Port installation. Small plastic injection ports get attached over the crack every 8-12 inches.
- Surface seal. A temporary epoxy paste covers the crack face between ports to keep injection material from leaking out as we pump.
- Injection. We connect the injection gun to the lowest port and pump material in until it appears at the next port up. We cap that port and move up. Material flows through the entire depth of the crack, from inside to outside.
- Cure and clean-up. Polyurethane cures in 1-2 hours. Epoxy 24-48 hours. We remove the surface seal once cured. The repair is essentially invisible afterwards.
Polyurethane vs epoxy
Polyurethane (the more common choice for water leaks):
- Expands as it cures, fills the entire crack including hairlines
- Stays flexible, accommodates future foundation movement
- Excellent for active water leaks - even bonds while water is flowing
- Cures in 1-2 hours
Epoxy (for structural cracks):
- Rigid, restores structural strength of the cracked section
- Used when the crack is structurally compromising the wall
- Slower cure (24-48 hours) and won't bond to wet substrates as well
- Higher cost but rare to need it
When injection isn't the right answer
We won't sell you injection if:
- The crack is structural and needs reinforcement
- Your wall is bowing and the crack is the symptom, not the problem
- You have multiple seepage points along the wall and a system would actually be cheaper than 8 individual injections
- The crack is in a block foundation where parging or stitching makes more sense
