Basement cracks appear in two locations: the concrete slab underfoot and the interior face of the foundation wall. Both need attention before moisture works deeper. We route and seal slab cracks with flexible material that moves with seasonal shifts, and inject interior wall cracks with polyurethane that bonds and flexes. Structural cracks get referred to our foundation repair team. Every visit includes a free assessment and a written quote.
Where Basement Cracks Start and How They Get Fixed
Basement cracks originate in two distinct places, each with its own cause and repair path. Floor slab cracks typically stem from concrete shrinkage as it cures or from settlement of the base underneath. These run vertically and allow water to seep upward from below the slab. Wall cracks on the interior face usually signal that the structural crack on the outside of the foundation is letting water through from the soil side.
The repair method depends on location. Slab cracks are routed open with a crack chaser to create a clean V-shaped or square channel, then blown clear of dust and debris. A flexible sealant is pushed full-depth into the routed channel and finished flush with the surface. Interior wall cracks receive polyurethane injection through small ports drilled along the crack line. The polyurethane bonds to the concrete and flexes with minor movement.
When a crack shows signs of structural movement, we identify it and recommend our foundation service instead of a basement-only patch. If water is actively entering, we pair the crack repair with basement waterproofing to address the root cause. This honest approach means the repair stays sealed.
Recent work
The repair sequence
How Basement Crack Repair Gets Done in Boston
Document and measure each crack
We photograph and measure every visible crack in the slab and along the interior wall face, then classify each as shrinkage, settlement, slab-only, or a sign of exterior wall movement.
Route slab cracks to clean profile
Slab cracks are opened with a crack chaser to a uniform V or square shape, then vacuumed and blown clean to remove all loose material and dust before sealing.
Seal or inject based on location
Slab cracks receive flexible sealant pushed full-depth and finished flush. Interior wall cracks get polyurethane injected through ports drilled along the crack, bonding and flexing as needed.
Why Basement Cracks Keep Coming Back Without Root Cause Work
Sealing a basement crack is necessary but incomplete if the underlying cause remains. A slab crack above an old plumbing trench will reopen unless the base is rebuilt. An interior wall crack weeping water will continue to weep until exterior drainage is improved or the structural issue is resolved.
Our approach identifies the cause alongside the repair. We explain what is driving each crack and what the lasting solution looks like. Sometimes that means a follow-up visit, sometimes a paired upgrade like a new slab over a rebuilt base, sometimes engaging foundation repair specialists. The quote reflects this honesty.
Slab vs wall cracks, sealing, injection, and when a basement crack means something bigger.
Yes. Slab cracks get routed to a clean profile and sealed with a flexible material that handles small seasonal movement. Wall cracks on the inside face get polyurethane injected through ports along the crack. The repair matches the crack.
Not always. Some are dry hairlines that are cosmetic for now but worth sealing before water finds them. Others are already wet and need the cause addressed, drainage, an exterior crack, or a structural issue, alongside the crack repair itself.
Yes. Horizontal cracks usually mean soil pressure is pushing the wall and the right answer is structural; we refer those to foundation crack repair on the engineered side rather than injecting from inside.
It will stop the leak at that specific crack. If the basement is wet in multiple places, the root issue is usually drainage rather than the cracks themselves; the right answer is also interior waterproofing to address the cause.
Most basement crack visits are a few hours to a full day, depending on how many cracks and whether they are slab or wall. The slab repairs cure within hours; injected wall cracks cure overnight. The timeline is on the quote.
Homeowner reviews
What Boston Homeowners Say About Their Basement Crack Repairs
Slab crack above an old plumbing trench got routed and sealed properly, and they said up front the base under it was the real cause. Honest call, the crack stayed sealed.
Q. B.
Boston
★★★★★
Three slab cracks and one interior wall crack all in one visit. They classified each, repaired each the right way, and the basement is dry through the season.
X. K.
Cambridge
★★★★★
They flagged my horizontal wall crack as structural and referred it up rather than just injecting. Could have charged me and walked away. Glad they did the right thing.
Z. E.
Quincy
★★★★★
Routed slab cracks instead of just smearing sealer on top like the last guy did. The repair has held through two springs of melt. Real method, real results.
F. V.
Somerville
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Describe the cracks you see in your basement, whether in the slab or walls, dry or wet, and we will assess them at no charge and provide a written quote for any repair work.
