First roof. Finished?

Hello all,
I have been pressure washing for 2 years now and am looking to add roofs. As always, I made sure mine was the first. I was initially concerned with the results. It was certainly not the before & after specimen I was hoping for. But reading through these feeds again has me thinking that I ought to reapply. Is this discoloration normal? And if, hypothetically, a relator needed it looking like new within 1-2 days, are there safe ways to help out mother nature and speed the process along?

Applied 5.5% SH with 1 oz/gal surfactant using a 12v. Let dwell 30-40 minutes. Rinsed with black tip (at a distance) using 5.5 gal, 2500psi machine.


I just wanted to verify that this discoloration is normal and nothing to be concerned about. Rather, I would probably need to re-apply SH until all the algae is the lighter color. Is that correct?

One of the first roofs I ever did was light grey with tons of stains. I am in the “no rinse” camp, not gonna go into it. But I went back the next day just to look, and the whole roof was this god-awful brown color. Thought I was going to be replacing the whole thing.

I ended up reapplying at 5% that day, let it dwell about a half hour, and walked the whole roof rinsing at around 60psi. It took hours, and I was freaking out.

Yes you can get fast results for a realtor, but you’ll need to know where the gutters go and it’s best to have someone drenching the ground to dilute the runoff. Price accordingly.

Before cleaning:

Oh geez what have I done?!

After a good rinse:


If it’s brown, it’s coming down. If it’s black, gotta go back.


Can you reword this so it’s a little more 2021 acceptable please?


You’re on fire tonite


I know. Gotta live up to the title ya know. Worked long and hard at this.

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Well done, Jake. Looks great. Except for that one spot but we won’t talk about that.

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Returned the next day and reapplied. Current appearance:

Any reason for concern here?

Don’t freak out, you’re gonna be fine. Needs a long, heavy rain or a good rinse to see what’s left under all the stuff you killed. Just let them know it’s not an immediate thing sometimes, and keep in contact with them.

So, the brownish yellow stuff is definitely going to come down eventually.

If you look towards the edge of the roof line you can still see a lot of black staining. That needs to be treated again to ensure that it actually goes away.

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Oh and watch that exposed metal there. It has a tendency to flash rust or spot up with SH. The runoff from a good hard rain may be enough to rinse it but if it’s just a drizzle you could have a problem with that.

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How did you arrive at your 5.5% target and what was your starting strength? To me it looks like you were being a bit shy with the application, I could start a bbq with 5.5%.

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Check back in a month or 2 unless you want to rinse. Agree with @DisplacedTexan - still looks like some black spots

will do, thank you

Good eye! I didn’t notice some of the remaining black areas. And that makes sense with the metal. Hasn’t rained yet, but if the next one is weak I’ll head back with a hose.

Filled a 55gal barrel with 30g of 10.5%SH and topped it off with water. You’re probably right that I went too light. It fizzed white pretty well, but there was just a lot of build-up to cut through.

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I would suggest you start using the 12.5% strength, no one knows what there getting at the end of the day, it’s just a label because they need one, that 10.5% could have been 6%. Start with the strongest you can source and go from there. I calculate my sh at 10% no matter what I’m mixing with 12.5 labeled stuff, easier to get an idea of strength and degradation when you always have the same round base figure. You can do it with 12.5% as well but I’m not a believer that it’s always 12.5, so i start at 10 to give me that “BS marketing” wiggle room.