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Old 07-09-2013, 08:46 PM   #1
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Pressure wash then scrape, or vice versa?


Hi,
I'm new to the forum. Thanks to everyone who reads and responds to my posts.
I have a 918 sq. ft. house that I'm prepping for exterior painting. The siding is T-111 (a type of plywood with grooves). Much of the south facing wall and parts of other walls have flaking paint that I need to remove. It makes more sense to me to scrape the paint first, then pressure wash. If I pressure wash first, then I'll have to wash the walls again to remove the debris from the scraping. Or do people think that the pressure washing will remove all the loose paint? Maybe pressure wash in conjunction with a stiff broom or brush?
Also, I want to use some kind of soap/detergent/bleach mix. I was thinking phosphate-free TSP (it exists), but I'm open to other suggestions.
Thanks for your time.

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Old 07-09-2013, 10:24 PM   #2
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Pressure wash then scrape, or vice versa?


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Originally Posted by psychopengy View Post
Hi,
I'm new to the forum. Thanks to everyone who reads and responds to my posts.
I have a 918 sq. ft. house that I'm prepping for exterior painting. The siding is T-111 (a type of plywood with grooves). Much of the south facing wall and parts of other walls have flaking paint that I need to remove. It makes more sense to me to scrape the paint first, then pressure wash. If I pressure wash first, then I'll have to wash the walls again to remove the debris from the scraping. Or do people think that the pressure washing will remove all the loose paint? Maybe pressure wash in conjunction with a stiff broom or brush?
Also, I want to use some kind of soap/detergent/bleach mix. I was thinking phosphate-free TSP (it exists), but I'm open to other suggestions.
Thanks for your time.
Figure on doing it twice either way, even if you scrape first the pressure washing will probably loosen more so more scraping. If you pressure wash first then after you scrap you will need to go back over it. Be careful pressure washing T-111 to much pressure can damage the wood. And just use a house wash for pressure washers.

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Old 07-09-2013, 10:28 PM   #3
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Pressure wash then scrape, or vice versa?


There's nothing wrong with doing the pressure washing after scraping. I have done that many times with siding that is in poor condition and lots of dust is made from scraping/sanding. Like you hinted at, you would really have to pressure wash twice if you are counting on the PW to remove loose paint, which, it really is not that effective at doing. You could use some krud kutter cleaner or no cleaner at all. The thing about cleaners is that they often leave a residue if not thoroughly rinsed off the siding. First try it without the cleaner to see how effective the pressure washing is. If you're not getting a lot of the dirt and mildew off that way, you could then add cleaner to your PW reservoir.
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Old 07-10-2013, 12:01 AM   #4
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Pressure wash then scrape, or vice versa?


I'll be renting a pressure washer, and I'll have to transport it in the trunk of my car, so it will be a hassle. I'd like to avoid having to rent it twice. Would it suffice that after the initial pressure wash and subsequent scraping, that I just hose down the wall with a garden hose and spray nozzle? Or will it need to be pressure washed again?
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Old 07-10-2013, 10:34 AM   #5
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Pressure wash then scrape, or vice versa?


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Originally Posted by psychopengy View Post
I'll be renting a pressure washer, and I'll have to transport it in the trunk of my car, so it will be a hassle. I'd like to avoid having to rent it twice. Would it suffice that after the initial pressure wash and subsequent scraping, that I just hose down the wall with a garden hose and spray nozzle? Or will it need to be pressure washed again?
Non-treated T111 absorbs water, detergents throught bare cracks and bare areas. I recommend you scrap off loose paint, sand any remaing ruff edges, brush off with a broom then wash with quick acting wood siding cleaner. After the cleaner has time to work (see cleaners instructions for time) then rinse twice (or per cleaners instructions) from top to bottom. Do not forget to also wash the fascia, eves and gutters. If over saturated T111 may will swedistorted story. Any windows my dry with spots or film. Ordinary window cleaner should clear them up.

Good luck
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Old 07-10-2013, 11:00 AM   #6
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Pressure wash then scrape, or vice versa?


I typically pressure wash first with cleaner/bleach solution, then scrape and sand. I don't find it to be necessary to wash again after scraping, and if fact I'm not so sure its a good idea.

After you do the scrape/sand an have removed all the loose paint, having the surface go through another wet/dry cycle is likely to loosen more of the old paint.

I've found it's important to get some primer on the surface as quickly as you can after prepping, it doesn't take long at all for paint that was tightly adhered when you scraped, to loosen up around the edges, especially if it gets wet.

My advice would be to wash, scrape, sand, dry clean the surface,(an electric blower and a broom work good) them prime as soon as possible.

I have had jobs get weather delayed during prep work, if it sits for more than a couple days, I almost always have to re scrape.
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Old 07-10-2013, 10:08 PM   #7
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Pressure wash then scrape, or vice versa?


It depends on how bad the surface is. If it seems like there is a lot of loose paint and there will be lots of scraping involved, then I would scrape first to avoid paint chips flying off. The same applies if you are dealing with lead paint as well, because you want to contain paint chips from flying and spreading around the property. If scraping seems minimal, then go ahead and power wash first.

Good Luck!
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Old 07-11-2013, 08:35 AM   #8
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Pressure wash then scrape, or vice versa?


I hate pressure washers! Everything on the exterior of your house is there to make your house waterproof. The clapboards, paint, flashing, caulking, roofing, windows etc, are all there to prevent falling rain from entering and damaging your home. Why then do people insist on blasting high pressure water at the house they have tried so hard to waterproof?
I scrape what's loose and then use a damp sponge to wipe down as I go. Oil based primer followed by two coats of good quality latex. No pressure blasting needed.
IMHO.
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Old 07-11-2013, 10:17 AM   #9
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Pressure wash then scrape, or vice versa?


be really careful when using a pressure washer. I just used one on my sunroom and it did some damage to the wood. I had to sand it down to get rid of the small indentations that it left. Made a lot more work for me than it had to be. I'd rather scrape than to use a pressure washer now. Then rinse with a hose.

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