Thought this is a great DIY Video for Deck washing
You may not actually need a new deck, but that old deck just may need a good scrubby and refinish on it. This Video will help you get that deck looking back in tip top shape.
If it seems like too much work you can call a professional, but for the DIY People out there this just makes sense to save you money. Not only that, you will appreciate the job more when you are finished with your deck.