Removing stains on rough cast

[bm]

My house is roughcast with the white spar (I think that is the correct term) and half way up there is a band of sandstone about 10ins wide After a number of years this sandstone has been discoloured and in places is quite dark Below this band at irregular intervals the roughcast has been stained Sometimes directly below the cement joining the blocks. I have cleaned the sandstone fairly successfully but in places the discolour is difficult to remove. It almost looks as if some substance has penetrated the surface I have tried bleach on the roughcast but was not successful. Can anyone suggest how I can remove the stains on the roughcast? It may be that I will require to get a professional to steam clean the surface Blair

[Phil L]

When you say 'roughcast' do you mean pebbledashed or tyrolean? - whichever it is, it can be painted but it's a horrid job, especially if it's never been painted before.

Forget about cleaning it as it's impossible