House Painting - when to power wash?

I'm going to paint our house, and I'm a little confused as when to power wash.
My first instinct says to do that first, gets all the dirt off, and the least amount of bare wood is exposed to aborb water.
Obviously, you should let the siding dry off afterwords before starting scraping, sanding and repairs.
But what about the dust raised from sanding? How do you clean that off?
Do I wash again? Is this not a problem? or something else?
Dave (trying to plan ahead).
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Dave,
My opinion, weather permitting, is to scrape and sand first then power wash regardless of bare wood. Let dry for 48 hours then paint. Another thought is powerwash, scrape and sand then use an air compressor to blow off the dust and clear out cracks and joints.
Good Luck.
There comes a time in the affairs of man when he must take the bull by the tail and face the situation. -- WCF http://www.utahhousevalues.com
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I suggest you wash first as a good power washing will remove a lot of loose paint. this will reduce your sanding time (and sanding dust) and the paint that stays on will not be going anywhere.

wash.
least
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Depends...do you want your paint job to last 15 years or 4 to 5? If you want 15, then never powerwash. Only scrape and (prime bare wood) and paint. If you don't mind painting regularly or plan to move in the next few years then I'd suggest powerwash, dry 24 hour, scrape & patch & wait another 24 before application of paint.
Powerwashing is the cheaper way out (short-term).
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Miles Kramer Your a moron of just bsn.. You wash, paint lasts longer....
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mark Ransley awoke from a drunken stupor and wrote:

Pot - Kettle - Black
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Ara Movsesians new name today Shoeless janet jackson
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That's ridiculous. How is powerwashing the cheaper way out? It takes longer to powerwash and scrape and prime than it does just to scrape and prime.
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Miles Kramer forgot how to remember
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Oops, my mistake...should read, hand wash with a medium bristly brush to remove mildew & grim THEN scrape, patch & prime. Powerwashing drives grime, mildew & water into the paint and can take weeks to dry in all but the driest climates. When moisture is trapped in the wood, a newly applied layer of paint will not adhear properly and can begin to flake in as little as 2 to 3 years. A properly prepped and painted house will cost about twice the amount as a powerwash prep type of job but will last much, much longer. And, it may be difficult to find someone willing to do the job properly.
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Its amazing how your response changed so dramaticly I see you speak from experience HAAA Ha. So how many years have you done this? How many hundreds of houses have you done? 0 for 0 , I will bet.. So you let it dry for a few weeks ,big deal, and mold, kill with bleach first, now about driving dirt " into paint" somebody been lian to you...And a properly preped house costing Twice as much as powerwash. This is one time I can say 100 % you do not know what you are talking about and you shouldnt, as it misleads people
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Agree, power washing is for concrete, unless you're a concrete guy, and they'd say it's not for that either.

wash.
least
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Here is a link that I found that might be helpful to you.
http://www.askbuild.com/cgi-bin/column?177
It suggests washing the house with detergent and water and not power washing.

wash.
least
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margie Kay , ,,Power washing works, soap can be applied, with power washer, and cleaned...It has been and is the recomended way by paint manufacturers. unless you have a serious problem.with chalk. . With the best of todays paints hand washing is not necessary. with cheaper paints any chalk is a problem. If you note on his site you refered it advertises Sears weatherbeater, made by sherwin williams, when purchased at sherwin williams it has a lifetime warranty and states it is designed to bond to chalky surfaces, as Sears does. Every job is different, and must be seen in person, the cleaner the better, but some paints bond to minor residue.
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In Charleston SC, power washing is always done with a cleaning agent, then rinsed. Without the cleaning agent, I have had mold growth below the new paint. We never wash the entire house - just one side at a time.
Tom Baker
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I get a kick out of this guy's advice. In the referenced column he says:
"Old houses were painted with oil based paints. These paints become more brittle with age. As the wood moves back and forth, the paint simply looses its grip. Even though you may scrape loose paint, a year or so later another spot on the siding may succumb to the forces of gravity and peel away. Fortunately I do not have oil based paint or primers on my 10 year old house."
Okay, don't use oil-base paint or primer. Oh, wait. In the column he links to:
"Oil based primers are superb products. These products penetrate deeper into wood fibers. Oil primers also do a great job of sealing woods like cedar and redwood that can produce bleed stains when coated with water based products. Primers are a must on bare wood and previously painted surfaces that have bad alligatoring, blisters, or the paint film is eroded. If your existing paint job is fairly smooth and sound, you do not need to use a primer over the entire surface."
Okay, so never use oil based primer but make sure you use oil-base primer...
There's tons of free painting advice available, most of it contradictory. Locally, power washing is a part of almost every paint prep job. It doesn't negate scraping, sanding and priming, it's just an additional step. But locally mildew is a big problem, freeze/thaw is non-existent, there's not a lot of wood siding left and the main enemy to your paint job is the sun.
Jeff
wrote:

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Miles Kramer you said, dont wash to make it last...that is quite a bit different , not to put down your father, who im sure did things right, but 30 yrs ago power washers were new, and oil was king. and I can see where people yrs ago not knowing power washers made alot of mistakes with oil. 20 yrs ago alot of old timers still would not recognise latex, even though manufacturers only guarnteed their latex line..times change. Every job is also different, you cannot generalize on prep. You must see and touch the old paint to know what you are up against, and how best to aproach it. So you dont rip off your customer.... Your house may have been chalking off so bad the ground had the same color... Ive seen it.. To say Double Cost for hand washing, I cant even think how in terms of labor how you could beleive that bs. I have only done high end work, use factory reps all the time,, following their instructions so on tough jobs I had their warranty.. and the customers had mine. you wrongfully scare people when you say dont powerwash. You did see on that reffered site the Sears weatherbeater, made by shewin williams, with lifetime warranty, is DESIGNED for chalking surfaces.remember Miles EVERY job is different...
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