Coral stone and keystone are classic South Florida materials, used on walls, columns, patios, and facades across older Miami neighborhoods. They are also soft, porous, and easy to ruin with the wrong cleaning. Treat them like concrete and you will regret it.
What makes coral stone different
Coral stone is formed from ancient reef and shell, which is why it is full of natural pits and pores. That texture is the look people love, and it is also what makes the stone fragile. It soaks up water, holds onto dirt and algae, and gives way under pressure that concrete would shrug off.
The two things that damage it
High pressure. Blast coral stone or keystone and you erode the surface, deepening the pits and knocking away detail. Low, controlled pressure is the only safe approach.
Acidic cleaners. Like travertine and marble, coral stone etches chemically under acid. A cleaner strong enough to speed up the job will leave dull, eaten spots that no future cleaning fixes. These surfaces need a pH-appropriate solution, not muriatic acid.
The right approach
Coral stone and keystone get cleaned with low pressure and a gentle, growth-killing solution, worked patiently rather than blasted. Because the stone is so porous, sealing after cleaning is usually worth it. A penetrating sealer slows down the staining and algae that this material attracts, and makes the next clean quicker and lighter.
If your home has coral-stone features, mention it when you book so the surface gets the right method from the start. We clean natural stone as part of house and exterior service, matched to the material rather than one setting for everything.
Common Questions
Can coral stone be pressure washed?
Only at low pressure. Coral stone and keystone are porous and soft, and high pressure pits and erodes the surface. They are cleaned more like travertine than like concrete.
Why did my coral stone turn dull in spots?
Usually acid. Acidic cleaners etch coral stone and keystone chemically and leave dull, eaten patches that do not buff out. These surfaces need pH-appropriate cleaning, never harsh acid.
Does coral stone need sealing?
It benefits from it. Coral stone is highly porous and stains easily, so a penetrating sealer after cleaning slows staining and makes future cleanings far easier.