A crack in your foundation does not always mean disaster, but it does mean you need an answer, not a guess. At Foundation Repair by Alex, we look at foundation cracks in homes across the Triangle every week, and most fall into a handful of categories we can explain standing next to the wall. This page covers why cracks form here, how to tell cosmetic from structural, and what actually goes into fixing it.
Why Foundations Crack Around Here
Wake County sits on a mix of clay and sandy soil, and that clay is behind most of the cracks we find. Clay absorbs water and expands when it’s wet, then shrinks back down once it dries out. Over months and years, that back and forth movement puts pressure on a wall or footing that was never designed to flex. A wet spring followed by a dry August can move that soil enough to open a crack that wasn’t there the year before. Sandy soil drains faster but erodes more easily, which creates its own kind of shifting ground underneath a slab.
Poor grading and clogged gutters make it worse. Water pooling against a foundation wall speeds up erosion and softens the soil under the footing. That’s the single most preventable cause of foundation cracks we run into, and it costs nothing more than an afternoon with a shovel and a downspout extension.
Reading Your Crack
Not every crack needs a contractor. Here’s the rough guide we use on every inspection:
- Hairline vertical cracks under 1/8 inch: usually shrinkage from the original concrete cure, cosmetic in most cases
- Vertical cracks between 1/8 and 1/4 inch: worth sealing, especially once you notice any dampness nearby
- Diagonal cracks running from a corner: often tied to settlement, worth a closer look
- Horizontal cracks, or ones that step across block joints: point to lateral pressure from soil pushing on the wall, and shouldn’t be ignored
If a crack is wide enough to fit a coin’s edge into, or it’s grown in the last few months, call someone. In the meantime, put a strip of tape across it with the date written on, check back in six weeks, and you’ll know a lot more than you do now.
Epoxy or Polyurethane: It Actually Matters
Some contractors grab whichever product happens to be on the truck that day. That’s the most common reason a “repaired” crack shows up again a year later. Epoxy injection bonds the concrete back together and restores structural strength, so it belongs in a dry, structurally significant crack. Polyurethane foam expands on contact with moisture and seals against water, but it stays flexible and doesn’t add strength back into the wall. Save it for a wet or leaking crack.
We use Sika epoxy for structural injections, since it has a long track record in poured concrete walls, and we turn to polyurethane products like PolyLevel when a crack is actively weeping water. When a wall shows early bowing alongside a crack, Emecole Metro carbon fiber grids let us reinforce that section without digging up the yard on the other side.
| Crack Type | Typical Repair | Estimated Cost |
|---|---|---|
| Hairline, dry | Monitor or seal | $0 – $350 |
| Vertical, dry, structural | Epoxy injection | $350 – $900 |
| Wet or leaking | Polyurethane injection | $400 – $1,000 |
| Bowing wall with crack | Carbon fiber straps or grid | $800 – $1,500 per strap |
| Active settlement | Piering or underpinning | $6,000 – $25,000+ |
Those numbers reflect national cost data for 2026, where the average full foundation repair project lands around $5,176. Most of the jobs we run in this area come in well under that figure, since a straightforward crack injection is a two to three hour visit, not an underpinning project.
What We Actually Do
On the first visit, we bring a moisture meter and a flashlight, not a sales pitch. We check the crack’s width, direction, and whether it’s active or settled into place. If it’s a straightforward epoxy or polyurethane job, we can usually finish it the same day. Small ports go in along the crack, low pressure injection fills the void from the inside out, and we grind the surface flush once it cures.
Structural cracks get a different process. We check the wall for bowing with a level, look at the footing where we can access it, and if carbon fiber reinforcement is called for, we install that before sealing the crack itself. Sealing first and reinforcing second leaves the wall unsupported while the epoxy is still curing.
One thing we tell every customer up front: a repaired crack doesn’t guarantee a new one won’t form somewhere else on the same wall if the underlying soil movement goes unaddressed. That’s why we look at grading and drainage during the same visit, even when the call was only about a crack.
When to Call Us
Call if a crack is wider than a quarter inch, if it’s growing, if water is coming through it, or if nearby doors and windows have started sticking. Those signs separate a $400 fix from something bigger down the road.
We work with homeowners across Wake County and nearby communities, and every estimate is free. Send a couple of photos of the crack with something for scale, a coin works fine, and we’ll tell you straight whether it’s a same day repair or something that needs a closer look in person.