How do I clean painted brickwork?

[MILdesperandum]

Previous owners painted our house exterior (mixture of bricks, render and what looks like stone cladding) and on the north side we're getting green algae like growth. What should we be using to clean it off?

You could try that stuff they use on paving to remove green slime, I suppose oc.hg.eu/products/show/id/662

Or a high pressure hose, have you tried that already?

Nope tried nothing yet, I walk past it and think "must do something about that" and then go inside and forget lazy

I know that feeling!

green is due to damp. Do the gutters or downpipes leak or spill?

A powerwasher will get it off. It will also take out perished or loose pointing, which needs repair anyway.

Usually if a wall is painted, it is to cheaply disguise something wrong with it. Once painted, you will have to paint it again, regularly, for ever.

You might perhaps have it rendered instead.

Thanks Piglet, The gutters and downpipes are OK I think. The worst affected is a (very old) flat roofed section which has a parapet wall.

does the flat roof drain fast, or does it suffer ponding? Could water be getting through the parapet?

I've not noticed ponding... will double check next downpour. Its a gravelled type flat roof if that makes any difference.