On this page
They are the two most common products people use on terraces, and the ones that ruin the most floors.
Bleach on outdoor floors
Bleach whitens algae so it disappears from view, but doesn't remove what's inside the pores: it comes back within weeks. It can also fade terracotta, stamped concrete and stone, harms nearby plants and leaves residue if not rinsed.
Hydrochloric acid on outdoor floors
It dissolves lime and cement, so it eats away joints. On limestone, marble, terrazzo and concrete it leaves burns and stains that can't be fixed. It also rusts nearby metal.
Never mix bleach and acid
Mixing them releases toxic chlorine gas. Don't use one after the other without rinsing thoroughly in between.
What to use instead
- Algae and moss: an outdoor biocide, left to act, then rinsed.
- Calima and embedded dirt: a technical alkaline cleaner and pressure with enough flow.
- Salt: a salt neutraliser.
- Oil and grease: a specific degreaser before washing.
FAQ
I already used acid and the joints are black. Can it be fixed?
Often, yes: they can be deep-cleaned and, if eroded, re-grouted. Send us photos and we'll tell you what can be recovered.