Roof Cleaning Questions

So, I just started doing roof cleaning with a soft wash system in January of this year. I’m in California. It doesn’t rain from mid May through October.

I did some roofs with concrete flat and barrel tiles with lichen. I treated them with 4-5% SH back in February. I went back to one of them today to see how the roof looked, and there was still lichen in many places.

So, my questions are these?

  1. How long does it take for the lichen to fall off the roof? Especially considering it rarely rains here, and when it does it is usually very light. Was my mix too light?

  2. If you lived in an area like mine, would you even use SH, or just use pressure to remove the lichen from the roof?

I feel like if I soft wash a roof now, there will be no rain for 6 months, and it will still be there in November.

The whole idea of not rinsing a roof is because you anticipate a decent rain at some point to take the lichen with it once it’s dead. Spray the roof nice and thick and rinse it. It has to be dead first.

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Even 3 months after I applied the SH, it would not rinse off. It took medium pressure to get it off. I can’t just rinse it off.

Do I need a stronger mix?

It’s one of 2 things, you either aren’t putting enough on to allow it to stay wet for any amount of time or your chemical margarita needs a review. 4-5% is a hot mix, with any lichen it will die when the roots soak up chemical and release. My roof mix is 50/50 no matter what’s on the roof with the exception of steel roofs. Never had any issues.

What do you mix for steel roofs?

Are they turning white? They need to be dead.

For painted steel roofs anything from a house wash mix to 2%, you would keep it wet and rinse heavily, same process as a house wash basically. Not uncommon to have to hit it twice.

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Concrete tile roofs are super porous, and on a hot day your mix disappears as soon as it hits the tile. On clay tile soft washing works great, but on concrete it’s a nightmare.

What’s the process on those soft concrete tiles?

Not soft, porous. They’re much easier to walk ok than clay. As far as cleaning, it’s controversial. I use a turbo nozzle on concrete tile. I’ve heard others say they soft wash them but, until I see video of it in southern California, I don’t buy it.