La Puce wrote:

saralove999 wrote:
(snip)
I think I

might need some sort of high power water jet but I dont know if that
will destroy the decking. Please help!

I use my power washer on everything (to which I get totally obsessed
with - once I start I won't stop even if my face is frekled with mud

My advice, wear goggles and wellies. You're going to get soaked (which
is also very much part of the fun). Don't use chemicals. There's no
need. You'll only damage your environment because the algea/moss will
return next winter anyway.

The non-ionic surfactant that is usually sold for pressure washing isn't
safe to drink, but it is relatively benign in the environment. Lots of
other common household products are much worse.

And using much larger volumes of pure drinking water with brute force is
probably at least as environmentally damaging as using a wetting agent.

If you can live with the smell for a while, spraying the decking with a
dilute solution of Jeyes fluid (or a real algicide) will work. Decking
is not a great choice in the UK since it rains too much. My N facing
paving always gets coated in green algae during the winter months.

Regards,
Martin Brown