First housewash help please🙏

First housewash scheduled for Thursday morning. Did a garage floor and a front and back porch on a condo last week, which was my first job. 4gpm belt drive machine… plan to dowmstream w/ SH and some laundry soap for a fresh smell. 1500sqft house with hardie shingle exterior. Its yellow and it does have a soft texture that i think is the beginning of oxidation but none came off onto my hand or fingers… she has dark algea growing on one side of the house and thats the real reason she wants it washed. So my thought is to communicate w/ her about the oxidation but assure her the mold/algae/organics will all be gone. What strength of solution would you run? Starting w/ 10% SH.

Very much appreciate any help🙏

I’m a vet as well…to be honest man I think with your experience level you’re playing with fire on this one. Hardie is nothing to be played with, if it’s anything but a light grey or ‘neutral’ color it can spot and streak very easily.

Aside from using laundry detergent, you’ll need to rinse the HECK out of that after letting the housewash mix do its thing and absolutely do NOT let it dry before rinsing.

It’s pretty obvious by the pic it’s sun damaged, don’t let the homeowner blame you for that.

Are you downstreaming?

Yes downstreaming… w/ the GP injector that came w/ the machine. I was thinking about filling the bucket 50/50 w/ 10% SH and water… isnt it supposed to be about 10 to 1? so 5% in the bucket would be .05% out of the wand? Am I right on that math? approximately?
I don’t know if it matters but the house was wet when I took that picture… It had just rained, and those darker areas felt wet. I hate to turn down the work… I’m 45 and pretty meticulous and careful… and can follow direction well… Maybe start at .025%? only one wall w/ organics… but, definitely value your opinion… if you think I should bow out, maybe I will… definitely don’t want drama and a big claim.

Ah gotcha, wasn’t aware it was wet.

Honestly the other guys can comment better than I can, but a lot of guys do cut their bleach using a 4gpm as it draws a lot harder than bigger machines. You are just using 10% though and depending on the age it may be less potent. Might just want to cut 25 water/ 75 SH and just be absolutely sure to keep misting that siding and rinse thoroughly. Generally speaking you want about .8% to 1% SH concentration for housewashes.

Again, the pro washers on here can comment further.

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Do a test spot first.


and a bucket test so you’re not relying on hypothetical math


See if they know what kind of paint is on house. Either way, find an inconspicuous spot and spray a little straight SH on it and let sit for about 10min to make sure paint doesn’t change colors. Sherwin - williams has a line of paint that used organics for coloring and so SH will cause color to change. Do you have a pic of the part with mildew on it?
50-50 with your 4 gpm should be about right. If mildew disappears in about 5min your mix is probably fine. If 1min, too strong, if 10min too weak unless really bad.


Thanks Racer! I will ask her about the paint… maybe they have some left from when it was last painted. Having the actual can would be ideal. Absolutely going to do a test spot. Here’s a couple more pictures. You can see the one wall with the mildew on it.

will do! :+1:

That’s not bad at all. Your 50-50 ratio should be good unless you’re using store bought SH, then maybe want to go about 60% SH mix.

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Be sure to test all those colors too…

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Thanks guys! Definitely will test all the colors… certainly the dark green now that I think about it… w/ the spray bottle Racer suggested. I did get the SH from the pool area in home depot, but it says 10% on the label. I think I found a source for 12.5 from a pool store about a half hour away. Right now just want to complete this job, do it well, and collect the money… then wash, rinse, and repeat… start improving a process. What do you guys think about blue plastic 55gal drums/barrels as buffer tanks… plenty large enough for my little 4gpm right? I was thinking of getting two, one for a buffer, and one for a batch mix 12v set up. Have to head that way in a few hours. Haven’t slept very well…lol buuuut we’ll get it knocked out! Thanks again for the help everyone, I’ll post the after pics this afternoon/evening… praying all goes well :pray:

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Well… i was there for 5 hours but I got it done… had a 30min lightning delay… i don’t mind a light rain but when it starts crackin and poppin I run for cover…lol Was able to use the machine for one side of the house, before I realized she had really poor water volume/pressure from her well so I finished it w/ a pump sprayer and her hose… and that sucked…lol plus I bid it via google and couldn’t see all the detail… she had have a soffet as such, the ends of her trusses were exposed and painted which created these individual cells w/ 5 sides that you had to hit… all the way around tbe house… and all the wood work on the porch… should’ve be a 500 dollar job, and I bid 299🤦‍♂️ of course if I couldve downstreamed it, it wouldve taken hapf the time… so maybe i was right on w/ the right equipment… what i shouldve done is check the water as soon as i arrived and immediately explained I wouldnt be able to use the machine and would have to do it by hand and it would take considerably longer and ergo would coast more for… but only because of the lack of water volume/pressure for her well… idk… how would you have handled it? What would be the lesson(s) I should take from this?

Thanks so much to everyone for the help!:saluting_face: Customer loved it and gave me a 25 dollar tip


Oh and there was mold on more than one side of the house… i was just going off what she said on tbe phone… it was all around under the eaves… and on 3 walls…lol

To be honest that is probably a one hour job for me. Once you get the proper equipment (downstreaming, buffer tank etc) you’ll just fly through jobs.

I would have rolled up, done a walk-around for a battle plan, unrolled hoses and once the buffer is at about 50 gallons go to town.

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I’d be at Starbucks networking on Myspace by then.

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Just looking at the photos, looks like you did a great job. Happy customer is all that matters.

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You can’t charge her because you didn’t have adequate equipment. A small buffer tank and you would have been fine. Turned out looking good, chalk it up to experience building.


2 places I haven’t been in decades… :rofl:


absolutely… the whole thing was a HUGE learning lesson… both jobs have been… I’m in an s10, so space is at a premium… but tomorrow I’m getting a blue plastic 55gal barrel for a buffer tank.