Orange stains on roof

I’m cleaning this roof and on the north sides of it there was thick black stuff, I didn’t think anything of it and sprayed away. After 10 minutes I go back over to those areas and these orange stains are showing now.
Any idea what this is?
I told the customer to call a roofing company and see if they’ve seen it before because Google didn’t give me any answers.

I don’t think telling the homeowner to call a roofing company to see if they’ve ever heard of it is the right call. Most roofing companies have no idea about how to clean a roof so won’t have the answers. Even still, you should be calling a roofing company. It was black and likely not very noticeable until you tried cleaning the roof. Now it’s orange and highly visible. Don’t leave it up to them to figure it out since they hired you to clean the roof. It might be different once you figure out the cause but I would still do all I can to figure it out and fix it. I definitely wouldn’t take a dime from them until their roof is clean.

Have you tried rinsing it? I’ve never seen anything turn that brown or orange but maybe it’s just some organic stain that was killed.

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Its normal in really bad areas. Hit it again still looks a little dark. It will come off in the next couple of rains

I hope your going to hit those other stains along the ridge line too.

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This picture was after only 1 pass with 3%SH, I was coming back to respray anything that didn’t come clean and there was these bright orange stains. Obviously anything that’s still black I’m going to continue spraying but I didn’t want to keep spraying and wasting my time and SH before finding out what this crud is. On the back of the house there is dark orange tinted stains that I haven’t sprayed yet, spraying them with SH turns them to a bright orange stain so I’m holding off until I can figure out how to get it off this section first.

They hired me to clean the black stains off of their roof, I didn’t notice the black stains on a couple portions were also orange tinted otherwise I would have tested a small area rather than spraying it all at once. I advised them to call a roofer so that someone could be here when they come by to look at it. Yes I’m going to do everything I can to get the whole roof looking great but considering I have no idea what it is, calling a local roofer who may have seen it before and know what causes it seems like the best option. I advised the customer to do so because they have a gated entrance to their house and I don’t want to be a middle man figuring out when the roofer and the customer can be there at the same time so he can get in to see it.

The customer had someone offering to paint/stain her roof a few weeks ago so i thought maybe that’s what this crud is and the SH just brightened the hell out of it. They bought the place less than a year ago so they have no idea what was done prior to that.

I’ve now sprayed that one section 4 times with 5-10 minutes between sprays and it looks basically the same, I’m going to try rinsing it with the pressure washer and see if it helps. I’ve cleaned many roofs that were much dirtier than this one and never seen orange stains like this. There aren’t even any trees near this section of the house so I’m perplexed.

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Why did you withdraw it your right. Its bleached. Could have even been a homeowner DYI thing. Literally 50% of my roof jobs the homeowner has YouTube it and failed by used a weak bleach/TSP/ spray and forget and gave up. Even caught one customer in a lie because his wife told on him :joy::joy:


I am going to go back tomorrow if it doesn’t rain and bump my mix to 4%, give it a few sprays and then rinse with the pressure washer. It’s chalky looking so I didn’t think it was just mold/mildew or algae.
The rest of the roof cleaned up great in 1-2 sprays so when this barely budged after 4 I figured it was something different.
Hopefully bumping the mix up and agitating it by rinsing gets rid of it.
That’s hilarious the wife ratted him out. My customers all just assume I’m going to be blasting the roof with high pressure and are surprised and slightly sketched out when I explain soft washing.

Lol damn your fast. I deleted it because after zooming in on the picture it does look somewhat abnormal. Probably just a bad photo

It probably needs to be hit with a stronger mix then rinsed. It’s organic if it bleached out so I wouldn’t panic.

Yeah the pic sucks, I took it from the ground and had to zoom in. If you hit the little pencil button next to your post it shows what you posted before deleting it.

Haha I’ve been here two years-ish and just learned something new. Nice

Take some more pics when you go back.

Ya he gave me a long story over the phone about how the guy who “washes” his house called the roof manufacturer and they told him how to safely clean his roof and nothing worked.

I asked what he used and he knew EVERYTHING his “regular house washer” did/used.

Turns out it was TSP/bleach applied with a pump up and rinsed with a garden hose.

I gave him the whole safe pressure blah blah blah speech and he gave the go ahead. When i came out he watched me closely and fed me some more crap about the “last guy” the whole time he watched me clean and talked. Half way through the wife pulls up and sees what i have already cleaned. She says " Wow Jason you should have called him weeks ago. You could have hurt yourself climbing around on that roof" he didnt watch me clean anymore. She wrote the check :joy::joy::joy::joy:


Haha. She crushed him inside without even realizing. That’s awesome. I bet you gained a life long customer there.
I’ll get some closer pics before I attempt cleaning it again. Looks like a storm is coming through tomorrow so might not get to it until next Sunday.

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Lightly wet it first to soften it, that crap has dried. Then treat whole section again with like 3.5-4%. Get the rest of the roof too. It’s obviously organic, you can see the stuff dead in there unless someone mudded their roof. Why would you leave a job with it looking like that. Did you try brushing, rinsing, F9 or anything? You don’t just walk away and leave a job looking like that. You’re suppose to be the professional. I’d crawl up there and scrub it with toothbrush before I left a clients house like that. If you’ve tried a lot of different things, then you post it looking for help. A lot of parts of the country have different lichen, mosses and algae. Literally thousands of different species.

You need to quit doing roofs for awhile.

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Quite a harsh response but I’ve picked up a lot of knowledge from your posts so I won’t take it too hard. This roof is as vertical as they make them and was covered in soap on a cool cloudy day. No way I was crawling up there, but apparently you are much more comfortable in dangerous situations than I am.
Had I not started this job later in the afternoon perhaps I would have had enough time to try a dozen things, but I didn’t. I cleaned the rest of the 6000sq ft roof and cleaned 90% of the exterior windows along with all of the interior windows and by the time I packed up it was dark outside.
I told them I would be back first thing in the morning to finish as long as it’s not storming and they were more than happy with how the other 90% of the roof turned out.
My question was simply if anyone had an idea what this chalky orange crud is before I started messing with it further. None of the hundreds of houses I’ve been to this year have had any resemblance of this stain on the roof so I came to the place people come when they need a second opinion.
I will give the things you mentioned a shot. I’ll even bring a toothbrush just in case all else fails.
I think I’ll continue cleaning roofs considering I’ve never had an issue up to this point, but I appreciate your input.

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Lonnie, don’t take it personal. But that whole section looks bad. You say you treated and then came back to it 10 min later. Why would you treat just part of a section and as @Grizz said not do the rest of it. I never leave a section until I’m pretty darn sure it’s done. I hate dragging my ladder back around to redo a section I’ve already done. The top part of that section hasn’t been touched and the section where your ladder is resting has lichen growing on it. Do you typically just spot treat roofs?

It’s steep but only one story there, so you could have rinsed with garden hose or shot some water up there easily in 5 minutes or brushed with a pole. And it’s definitely not dark when you took pic. If it wasn’t there when you started, then your responsibility. And if it was just a real dark area then it turned, then obviously organic.

The reason I made the prior comment was I’m questioning your spraying technique. I’ve never done or seen anyone spray the lower 60% of a roof and not do the rest if it needed at the same time.


So how did it go?