A pink, rust or salmon bloom across block paving is normally red algae - a light-tolerant organism that thrives on open, sunny driveways where green algae struggles. It is often mistaken for iron staining and treated with the wrong product as a result.
Algae or iron?
Red algae covers broad areas evenly and sits on the surface. Iron staining is patchy, radiates from a point such as a fixing or an aggregate particle, and does not lift with a biocide.
This guide sits under our Patios & Driveways work, covering 20-mile radius of Plymouth.
Why washing alone fails
Rinsing removes the colour for a few weeks and then it returns from the spores left in the block's pores. The treatment has to reach into the block, which means dwell time, not pressure.
Sealing afterwards
A clean, dry, treated driveway can be sealed to slow regrowth and stabilise joints. It is optional, and we will tell you when a driveway is too degraded for sealing to be worth the money.
Questions we get on this
- Does red algae damage the blocks?
- No, it is a surface organism. The issue is appearance and, when wet, grip.
- Will the blocks come back to original colour?
- Close to it, though sun-faded blocks stay faded - cleaning removes growth, not UV fade.
- Do you re-sand the joints?
- Yes, kiln-dried sand goes back into the joints as standard after a full driveway clean.
Related reading
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