Cracks in a Raleigh Foundation: Which to Seal, Which to Watch

Sealing a single foundation crack typically costs $200–$1,000 with epoxy or polyurethane injection (Fixr, 2026), and This Old House lists $250–$800 for crack filling. Sealing stops leaks and closes gaps, but it does not stop movement. A crack that keeps widening needs its cause found first, which can mean drainage work or piers.

Reading the crack before foundation crack repair

• Hairline and vertical in a poured wall or slab: usually shrinkage from when the concrete cured. Fine to seal if it leaks; otherwise watch it.
• Stair-step through brick or block mortar: one part of the wall has moved down or out relative to the rest.
• Diagonal from a door or window corner, wider at one end: points to settlement under that section.
• Horizontal along a block basement wall: soil pressing from outside. This one needs prompt attention.
• Offset, where one side sits higher than the other: movement across the crack, not just a gap. Always worth an assessment.

How can you tell whether a crack is still moving?

Mark both ends with a pencil line and the date. Measure the widest point with a ruler or a crack gauge card, and photograph it with the ruler in the frame. Check again after a long wet spell and again after a dry one. The NC Geological Survey notes that clay soils swell when wet and shrink when dry, so a crack that opens and closes with the seasons tells a different story from one that only grows. A few months of notes will make the first conversation with a specialist far more useful.

What the repair involves

Epoxy injection fills a crack in poured concrete through small ports and bonds the two sides back together. Polyurethane injection stays flexible and is chosen when the aim is to stop water. Repointing replaces cracked mortar in brick or block once movement has stopped. Slab cracks are usually cleaned and sealed.

None of these holds a foundation that is still settling. If the pattern points to a corner or wall going down, stabilizing it comes first, and the page on house leveling and piers explains how that works.

Before the specialist visits

List every crack you know of, inside and out, with the date you first saw it. Note where the nearest downspouts empty and whether water stands near the wall after storms. Mention any doors or windows that have started to stick. Then look over the typical costs for crack sealing and structural repairs so the numbers you hear have some context.