Hello Norma,
A few things to consider when doing a house wash in a diy situation, windows, d-glazed (upvc) or wood same with the doors. What sort of dirt is it? regular dirt ie atomosphere or alage etc. Any chance you could post a photo of the house/walls, and I'll try to help. DIY pressure washers (Argos, B&Q etc) are fine, and don't take offence really should be used for just cleaning cars, for a pro job, a pro machine and user is needed.