Pressure washing a house.

BigNick73 said:

best house wash is a bleach mix 1 part bleach to 3-6 parts water depending on how bad the mildew and crap is use a garden sprayer to apply and rinse off with a water hose.

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I ran a PW company for 3 years. The base of most professional house wash mixes is 0.75-1.00% bleach (on the wall). 1:3 (1.34%) is a bit too strong (unless you are buying dollar store bleach) and you risk killing plants and chalking siding. Add a good bleach stable surfactant and you can clean 95% of what you need with a 0.75% mix. Use a proper house wash formula (about 7 components, some not available at retail), and you can clean any house at 0.5-0.75% bleach.

One other note for the DIY house washers listening. Nick is dead on about cleaning a house at garden hose pressures. Ignore all the BS the guy at home depot tells you about needing 6 billion psi to "blast away the crud". That's the language of the ignorant. Pro's use use 3000 psi machines to clean 50ft gables from the safety of the ground. The actual working pressure at the surface is typically less than 100psi. Your 3.0 gpm machine (we use 6+ gpm) won't throw that distance anyway, so the difference between 2500-3500 psi is negligible to a homeowner.

One last note: The box box stores LOVE to print big numbers and state that "Cleaning Units" = pressure * volume. For those few jobs that require high pressure (i.e. heavy grease removal), cleaning efficiency is better approximated as volume^2 * pressure * water temp. Plug that into the HD brochure and see how they compare.

Interesting. What is your take on those things you can buy to screw onto the end of the hose, labeled "House Wash" or something? I think Windex makes one.

I need to wash my house, it is dirty and have some spots of green. I should have done it in the spring/early summer before they started outdoor water restrictions. Towards the end of summer I could clean my own house but if I hired a pro, they could come use my hose and do it but I didn't want to pay someone for something I can do myself.

Go to a sherwin-williams and buy some Bio-Clean. It's a biosafe mildew and moss treatment that works wonders and doesn't harm plants or streams. We used it for years while painting houses.

Yeah you do have to watch the plants 1:3 was the absolute strongest we went (lots of mildew) and we always used the cheapest bleach available. 1:6 was normal. Never had any problems with either mix, wood siding is almost unheard of down here it's 90% brick and stucco and occasional bit of vinyl siding, wood siding just goes to crap in the high humidity. For the plant part if we using the stronger mix we'd follow it up with plenty of water to try and rinse most the bleach out of the immediate area and dilute it even more of course we would wet the house, bleach it and then rinse, bleach wasn't on the house more than a minute or two (just long enough to watch the mildew turn orange) before lots of clean water followed it rinsing it all clean, I'd imagine the bleach to water mix once it reached the ground was negligible.

If anyone tries this we used 3 gallon garden sprayers for bleach application and be careful cause if using the 1:3 mix it really irritates the skin after a while.

It was interesting watching my previous house being pressure washed. I don't know what psi it was running, but it was enough to dig most of the dry-rot out of the wood. Punched a hole through the siding in one spot.

My house is white vinyl siding, pretty thin. I use a cheap pressure washer with HOT water, TSP and bleach. It doesn't kill the grass or shrubs. I use a long handle RV wash brush to break loose the thick stuff.
Not feasible for most, but hot water makes a huge difference. The pressure washer really just launches it high enough to get the 2nd story.
BTW, this combo works great for plastic outdoor furniture and yard toys (the little tikes playhouses...).

Beerrific said:

Interesting. What is your take on those things you can buy to screw onto the end of the hose, labeled "House Wash" or something? I think Windex makes one.

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The ones for windows aren't bad, but the ones for a house are horrible. It's dry pool chlorine in a dispenser. Perfect for chalking up paint/siding (and usually windows).

Klainmeister said:

Go to a sherwin-williams and buy some Bio-Clean. It's a biosafe mildew and moss treatment that works wonders and doesn't harm plants or streams.

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Never tried it, but two things come to mind. First, to kill moss and mildew you need a bio-cide. There is no such thing as a bio-safe bio-cide. I suspect it's formulated with a much wider margin of error, but if it works it's still a plant killer. Second, it's not good enough to just kill the organic material or bleach it white, but you must also remove it and the dirt.

BigNick73 said:

1:3 was the absolute strongest we went (lots of mildew) and we always used the cheapest bleach available.

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The "cheapest bleach" decision was a blessing to you. It is typically only 3% while good bleach is 5%. Thus, you were maxing out at 0.75% Had you tried that with good bleach, or "ultra" (often 6.25) you would have a much bigger problem with burnt plants.

BigNick73 said:

if we using the stronger mix we'd follow it up with plenty of water to try and rinse most the bleach out of the immediate area

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Rinsing after helps, but the key to plant survival is rinsing before. Bleach on a dry leaf will do damage in seconds that cannot be rinsed away.

david_42 said:

It was interesting watching my previous house being pressure washed. I don't know what psi it was running, but it was enough to dig most of the dry-rot out of the wood. Punched a hole through the siding in one spot.

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You have just found our what happens when you hire the lowest bidder. I used to get at least one call a week asking me to repair damage done by the homeowner or the low bidder. You should have heard the responses when I explained that what they were looking at was permanently damaged.

5isnotenough said:

My house is white vinyl siding, pretty thin. I use a cheap pressure washer with HOT water, TSP and bleach.

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Speaking of permanent damage...

With about 2000 homes under my belt, I can say without a moments hesitation that hot water is totally unnecessary in residential pressure washing (with the exception of flat concrete). Not only does it damage wood (decks, trim), but the temperature at which vinyl siding deforms is just a few degrees above that at which it does not. The really sick part is that by the time you see it start warping, it's too late to stop it from happening over a large area.

You have just found our what happens when you hire the lowest bidder. I used to get at least one call a week asking me to repair damage done by the homeowner or the low bidder.

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Actually wasn't the low bidder (I never hire the low bidder OR the high bidder) and he said removing dry rot with a pressure washer got more of the fungus out. He then treated the areas with an epoxy stabilizer and wood filler before painting. The areas were the rot went all the way through got replaced.

david_42 said:

Speaking of permanent damage...

With about 2000 homes under my belt, I can say without a moments hesitation that hot water is totally unnecessary in residential pressure washing (with the exception of flat concrete). Not only does it damage wood (decks, trim), but the temperature at which vinyl siding deforms is just a few degrees above that at which it does not. The really sick part is that by the time you see it start warping, it's too late to stop it from happening over a large area.

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I'm sure it is, but it sure is nice when all you've got is a piece of crap pressure washer! (BTW, not much that I do is ~necessary~)

david_42 said:

Actually wasn't the low bidder (I never hire the low bidder OR the high bidder) and he said removing dry rot with a pressure washer got more of the fungus out. He then treated the areas with an epoxy stabilizer and wood filler before painting. The areas were the rot went all the way through got replaced.

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Oh... He *intended* to blow it away. Normally, when I hear about a PW'er damaging wood it's because some hack is out there destroying homes for $99.00

5isnotenough said:

I'm sure it is, but it sure is nice when all you've got is a piece of crap pressure washer! (BTW, not much that I do is ~necessary~)

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Just be very careful. I wouldn't recommend a degree over 125*F. I've known several people who made multi-thousand dollar mistakes combining hot water and vinyl homes.