Most leaking cracks in Buffalo's poured concrete foundations are vertical shrinkage cracks that can be injected from inside in an afternoon. Some are not, and the difference matters. We tell you which kind you have before anything is sealed.
Tell us what the Buffalo property is doing and we'll take a look.
Concrete shrinks as it cures, and a poured wall that is restrained by its footing relieves that shrinkage by cracking, usually vertically or at a slight diagonal, often near a window or a corner where the wall is thinnest. Those cracks are common in the 1950s-through-1990s poured foundations of Amherst, Clarence, Orchard Park and Grand Island, and they leak because clay backfill keeps them wet for half the year.
Buffalo adds two stresses of its own. The first is frost. NOAA's normals give the airport about 124 days a year at or below freezing, and the soil survey notes that frost action is a threat to shallow foundations on the county's silty and clayey soils. Saturated clay expands when it freezes and pushes on the wall; it relaxes when it thaws. The second is the clay's own behavior: the Erie County survey describes the Odessa-Schoharie-Rhinebeck soils as very sticky when wet and cloddy when dry, which is what a shrink-swell soil looks like in the field. A wall that is loaded and unloaded every year eventually shows it.
Settlement cracks are a different matter. The survey observes that many homes on the Urban land-Niagara complex show signs of settling because of low soil strength and frost heaving. Those cracks are often diagonal from a corner, wider at one end, and sometimes offset. They are not simply injected and forgotten.
For a non-structural crack in a poured wall that is leaking water, the repair is injection from inside. Surface ports are set along the crack, the face is sealed with a fast-setting paste, and a low-viscosity polyurethane is injected under pressure. It travels the full depth of the wall, reacts with the water in the crack and expands into a flexible seal that stays bonded as the wall moves slightly with the seasons. This is the right material for a crack that is wet and may move.
Epoxy injection is used when the goal is to restore the wall's strength rather than to stop water alone: a crack that has been evaluated as structural and is no longer moving, or a crack that will be carrying load after a wall repair. Epoxy is rigid and welds the concrete back together, but it does not tolerate movement and does not bond well through active water, so the wall has to be dry and stable when it goes in. Choosing the wrong one is the most common injection failure we see.
Injection needs a solid wall with a single crack to fill. A rubble stone foundation from the 1890s on Buffalo's West Side or in the older parts of Lackawanna and Tonawanda is thousands of joints, not one crack, and block walls are hollow. For these, crack repair means repointing failed mortar joints with a mortar compatible with the original (soft lime mortar for stone, not hard portland cement that spalls the stone), rebuilding sections where stones have loosened, parging the interior face where appropriate, and then draining the base so the wall is not asked to hold back water it was never built to hold.
Where a block wall has cracked along a mortar line horizontally, that is a wall under lateral pressure and belongs on the bowing wall page, not here. We will say so if that is what we find.
The quick signs: a hairline-to-eighth-inch vertical crack that is the same width top to bottom and shows only water is almost always shrinkage. A crack that is wider at the top than the bottom, runs diagonally from a corner, has a horizontal component, or shows one side displaced from the other deserves a closer look. So does any crack that has grown since you first noticed it, or a stair-step crack in block. We measure and photograph cracks on the assessment and will tell you plainly whether the repair is a seal or something more.
If a crack is structural, the honest sequence is to stop the movement first, with piers, anchors or carbon fiber depending on the cause, and to seal the crack second. Sealing a moving crack buys a year and then fails.
Questions
A properly done polyurethane injection in a non-moving crack is a permanent repair for that crack. It will not prevent new shrinkage cracks elsewhere, and it will not hold if the wall is actually moving, which is why we assess the crack before injecting it.
Injection needs access to the full length of the crack from inside, so a section of drywall along it has to be opened. The alternative is exterior excavation at that spot, which avoids the interior wall but costs more and depends on what is outside.
Floor cracks are common and usually harmless unless water comes through them, which points to the water table under the slab rather than to the crack itself. That is a drainage and sump question. A floor crack with heave or displacement is worth a look.
New concrete cracks as it cures; vertical hairline cracks in the first year or two are normal. Have them injected if they leak. Cracks that widen, run diagonally or show offset are the ones to have evaluated.
Call the local line or send the form and we will set up a free on-site assessment with a written scope and no obligation.
Request a free estimate Call (716) 325-5837