Exposed shell concrete finish in Florida

This is the one that looks like what it is made of. Rather than grinding the plane flat, the surface is opened up so the shell stands proud — additional shell is broadcast onto the fresh pour and seeded in, then the top layer of cement paste is taken back to reveal it. What you end up with is aggregate you can read from standing height and feel through a bare foot.

It is the most obviously coastal of the three by a distance, and the one people picture when somebody says the word.

Grip is the point

Texture at the surface is what stops a foot sliding, and this finish has the most of it. That is why it turns up in the places where a slip actually matters: entrance steps, pool coping, the transition from deck to lawn, walkways that run through irrigation spray, and driveway aprons that pitch toward the street.

Coping is the clearest case. It is the one edge in a pool that everybody grabs, kneels on and climbs over, wet, all summer. A textured edge there is worth more than a comfortable one.

What it costs you

Comfort, in two specific ways, and both are worth knowing before rather than after.

It is not a lie-down surface. Sunbathing on aggregate, or kneeling on it to plant something, is a different experience from doing either on a honed deck.

And it is not a furniture surface. Chair feet find high points, tables rock, and anything dragged across it catches. If the area is going to hold a dining set, this is the wrong finish for that part of it — which is a real and common answer: exposed shell on the walkway and coping, honed on the terrace where the table goes. One pour, one material, the finish varying by what each area is for.

Keeping it clean

Texture holds more than a flat plane does. Sand, leaf litter and pollen sit in it rather than blowing off, so it wants a hose more often than the other two, and a stiff broom rather than a soft one.

Get to organic stains early. Leaves and berries left on any pale surface through a wet week are the marks that end up permanent, and that is more true here because there is more surface for them to sit against.

Never acid-wash it. Muriatic acid attacks the shell faster than the matrix holding it, so what starts as a cleaning job ends as a texture change you cannot undo.

Sealer, as with the other outdoor finish: penetrating, breathable and matte. A film-forming product does something particularly counterproductive here — it partly fills the texture that is the entire reason this finish was chosen. The sealing post goes through why.