Advice with prep and painting rough effect rendering.

[Thandeka]

Our extension is rendered with the rough effect stuff. It is a dirty mustard colour and minging- it also is a bit grubby but scrubbing with strong brushes doesn't do much. One google site said you need to jet wash it and leave to dry for ages as part of your prep - another site said never ever do that as it will push water into any cracks and cause internal problems and when you paint over you will seal in any water- causing damage.

The extension is over 30 years old and a bit dodgy but still has life in it- I am wary about jetwashing as don't want to cause any problems. but how can I prep the surface ready for painting? Or can I just paint over it all and hope for the best? (I can't see how we would ever get the surface "clean" for painting.)

Think we will be painting it an off white.

Any tips?

[Thandeka]

Anyone?