Never, ever, ever pressure wash a house. Nothing on a house is designed to withstand anything stronger then a garden hose. While you might make what you are washing look pretty, you are destroying your seals, your paint and putting water into places that it's not supposed to go. Then it just sits there and either turns to mold, or starts the process of rot. Mositure is also what bugs look for when invading a house, and what the flying termites are trying to find when establishing a new colony. It can take weeks or even longer to dry out!!!
This Old House had a really good episode that showed how much water got into the house from pressure washing it. If I remember correctly, they waited a month and then cut open the walls to show what was wet and how wet it still was.
To wash a house, you have to use a house cleaning detergent, a scrub brush and a garden hose. Anything more and you will damage your house.
Eddie