Why Are There Pits and Holes Forming in My Concrete?

You’re seeing pits and holes because something in or on the surface is breaking down. Most often, water and salts keep the slab saturated and weaken the top paste. Sometimes a weak particle or contaminant pops out later.

Even when concrete feels “cured,” the surface still takes weather and traffic day after day. So they might not show up until weeks or months after the pour, and they tend to cluster in wet spots or around isolated cone-shaped pop-outs. In this guide, you’ll name what you’re looking at (pits vs. pop-outs vs. spalling), so you don’t go down the rabbit hole. Then you’ll match it to the most likely coastal North Carolina cause, like a dock board that never quite dries out, and decide when a simple clean and sealer is enough versus when you should document it and call a pro or the original contractor.

Pits, Pop-Outs, or Spalling?

If you name the pattern wrong, you’ll chase the wrong cause and the wrong fix, and that’s a guaranteed waste of time, This Old House style. First, classify the kind of surface loss you’re seeing.

Pits are lots of small pinholes or shallow craters, often fairly uniform across an area. Pop-outs are distinct, cone-shaped “plugs” that break out, typically about 1–3 inches wide and you may find a little stone-sized void at the center. Spalling is broader flaking or chunking where the top layer lets go, often showing up along edges, joints, and spots that stay wet after Wilmington-style rain.

Why Are There Pits and Holes Forming in My Concrete?

In coastal North Carolina, the most common driver is chronic wetness (concrete pits and holes): when a slab stays saturated from shade or poor drainage, the surface paste weakens over time and you get widespread fine pitting in the areas that hold water. Next is salt and chlorides (ocean air and pool splash-out) that make wet concrete more vulnerable, especially along edges and joints (see ACI guidance on deicer-related deterioration mechanisms).

If the damage looks like distinct 1–3 inch pop-outs, suspect porous or reactive aggregate or small contaminants that later break free (concrete pop-outs causes). Don’t default to “normal wear” if a newer slab keeps shedding cones; that pattern often points to materials or finishing and is worth documenting early.

Salt-laden coastal air can speed up material breakdown anywhere moisture lingers, so patterns that repeat in the wettest spots are an important clue. Read more in our article: Signs Salt Air Wind Damage Shingles

DIY Fix vs. Call a Pro

A patch can look perfect for a week, then the damp spots return and the holes open back up in the same locations. The difference between a lasting repair and an endless re-patch loop usually comes down to a few quick tells.

You can usually DIY if the spots are shallow and isolated, and you can clean them out to solid concrete, but don’t wing it: treat it like the Home Depot / Lowe’s bagged-mix aisle and do it right the first time, then scrub, rinse, let it dry, patch small voids, and seal the surface so pits don’t keep holding water. After a hard rain, do a quick check instead. The same areas stay dark and wet for hours. If yes, fix drainage or sprinklers first or your patch won’t last.

If water is sitting where it shouldn’t, fixing flow paths like gutters and downspouts often prevents the same wet areas from reappearing after every storm. Read more in our article: Keep Gutters From Backing Up

Call a pro (or the original contractor, if it’s newer) if the holes multiply quickly or you see 1–3 inch cone pop-outs across the slab; edges/joints are chunking, cracks show vertical offset, or you get rust staining that keeps returning after cleaning. Don’t write those off as “normal aging.”