coaming

Imagine the deck of a boat in rough weather—you don't want waves washing across the deck and pouring straight into an open hatch. That's where a coaming comes in. It's a raised border, like a short wall, built around an opening on a vessel (such as a hatch or companionway) to keep water from getting below. It also gives a sturdy edge for covers, hatch boards, or seals to sit against.

And it isn't just for boats. In building and roofing work, a coaming can mean the raised curb around a roof opening—like a skylight or roof hatch—designed to shed water and create a solid, weather-tight frame. In both settings, the idea is the same: a raised rim that helps keep the outside out.

A coaming (pronounced "KOH-ming") is a raised, usually vertical rim that extends above a surface to frame an opening. On a vessel, it rises from the deck around openings such as hatches and companionways (and on some small boats, around the cockpit) so that waves and spray washing over the deck are less likely to flow straight down into the interior. It forms a barrier against water, and it also provides a firm edge for hatch covers, boards, gaskets, or a spray skirt to seal against.

Historically, coamings were often made of wood, but modern vessels commonly use metal, fiberglass, or other composites. They aren't only functional; as part of the framing around an opening, they can also add stiffness to the surrounding structure.

Beyond maritime use, the same idea appears in construction: a coaming can be the raised curb around a roof opening (for example, beneath a skylight or roof hatch), intended to keep water out and provide a secure mounting surface. The term is often linked to "comb" in the sense of a ridge or crest—an apt image for this raised edge standing guard around an opening. So when you notice a protective rim that helps keep water from sneaking inside, you're looking at a coaming doing its quiet, practical job.