Washing walls

[bikeit]

I will soon be painting the exterior of my house which is rough render, so should i wash the walls down with a pressure washer at a moderate power before i start painting.
is there anything that i could put in the water bottle of the pressure washer that could be applied to the walls to make removing green algae easier and quicker?

 

[misterhelpful]

A mild bleach solution can be used to remove/kill the algae but I wouldn't recommend putting neat bleach into the pressure washer bottle for washing walls because you won't have control of the spray as you would if you were washing the floor, for example.

I like to use an old roller dipped into a bucket of the bleach solution and applied to the walls, leave for half an hour and then use the pressure washer to rinse it off.

Of course, you could substitute the bleach solution for a fungicidal wash, which is purposely designed for the job and removes the stubborn stuff better, but bleach is cheaper and goes a lot further.