Patio flag cleaner?

my patio flags havent been cleaned for a good 10 yrs ive spent 3 hours cleaning them with a pressure washer,probably an area 5m x 5m and it was difficult,hardest thing to remove was some green spots on the flags,im assuming this is algae?

Id like to go over it again to get rid of every mark possible so whats a good cleaner for this sort of thing,any comments appreciated
thanks

 

Dunno about the cleaning stuff, but I believe (once you've got them clean) that you can seal them which makes cleaning them easier.

 

Three options, Hire an industrial pressure washer or get someone in with one, these are not the same as the cheap B&Q karachers and operate at two or three times the pressure and water flow.

With the turbo lance on mine and at full pressure it will literally drill into a surface if you keep it on the same spot.

Option two is to treat the surface before and after with a bleach solution, Hyperclorite from a farmers merchant sprayed on neat up to 50/50 dilution with water works and will kill of algal growth. Wear a respirator and visor.


Option three is to use an algaecide, spray it on, leave for a month or two to work then wash to remove any algal traces and reapply as a preventative.

I use ecotherm regularly, particularly on shaded courtyard areas, this works out a cheaper option than pressure washing, I tend to wash these areas every two years to remove ground in dirt however on the treated areas there is no algae or lichen:

http://www.amenity.co.uk/webstore/product_info.php?cPath=1018&products_id=111

 

i have indeed purchased from your link the algaecide,look fwd to using it

thanks

 

Every Spring we kill off the moss and algae with a solution of household bleach and then about 10 ten days later blast off the dead stuff with a pressure sprayer and follow up with a stiff brush. Killing the moss and algae is easy. Getting it loose is the hard work bit!

 

thanks dave most helpful but i have ordereed the algaecide in pro gards link

thanks again useful info