My house has a patio area outside the back door. The patio borders onto grass and makes a home for a pair of sheds. It doesn't drain well and is always in the shadow of the house, so that it stays damp long enough for algae to grow, leaving the area slimy and treacherous.

I clean the algae off the slabs when the weather is dry, but it grows back quickly as soon as it becomes damp again. Living in the UK, this is more often than is tolerable.

Long-term, I want to replace the entire area with something that drains properly and is dry enough to stop the growth completely. Until then, is there anything that can be done to inhibit the algae?

  • 1
    copper salts are very poisonous to algae. they sell them for this purpose, for ponds and aquaria. – Grady Player Feb 18 '13 at 20:46

Not really, if water is pooling in the area, or it remains damp and sunless, particularly in our wet winters. On roof slates or walls, the addition of a copper strip at the top, so that any water running down contains a minute amount of copper, inhibits algal growth or stops it altogether, but that's not going to be effective in the area you describe. I'm afraid you're stuck with cleaning it off whenever you get the chance.

  • Yes it sounds like drainage is the only long term solution. Perhaps some kind of rubber mats could be put down temporarily as a stop-gap to make it safer. – winwaed Feb 18 '13 at 13:14

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