What causes the green growth?
Algae and moss thrive where there is moisture. Areas that remain damp for long periods provide ideal conditions for growth.
Several things can make a surface more susceptible:
- Shade from buildings, fences or trees
- Poor drainage
- Regular rainfall
- Moisture that doesn't dry quickly
- Dirt and organic debris accumulating on the surface
This is why one part of a patio or driveway can remain relatively clean while another becomes heavily covered in green growth.
Why does it keep coming back?
Cleaning removes the existing contamination, but it doesn't necessarily change the conditions that allowed it to grow in the first place.
If an area remains damp and shaded, algae and moss can gradually return.
This doesn't necessarily mean the original cleaning wasn't effective. It simply means the environment is still suitable for organic growth.
Can pressure washing remove it?
Pressure washing can remove a lot of visible growth from suitable hard surfaces. However, simply blasting the surface with water isn't always the complete answer.
Depending on the surface and the type of contamination, a suitable cleaning treatment can help break down organic growth more effectively.
The important thing is to avoid assuming that every green surface should be treated in exactly the same way.
How can you reduce regrowth?
Keeping surfaces reasonably clear of leaves and organic debris can help, as can improving drainage where possible.
You may not be able to change how much shade an area receives, but regular maintenance can stop organic growth becoming heavily established.