Average amount of bleach used on a 2000sq. ft. roof

Can anyone tell me what the average amount of bleach is used for a 2000sq. ft. roof? Or better yet, what is the amount of bleach used per sq. ft.?

Depends on so much. What’s the pitch? What’s the roof made of? Is there moss or just the black stuff? What are you applying it with? What surfactant are you using?

I’d bet on 15-20 gallons with a good, thick surfactant


Thanks Jake, I realize there are multiple factors. The reason for my question is I’m putting together a small trailer for roof washing. Just wanted an idea on tank size. Thinking 25gal. tank for bleach, 25gal. water tank and 5gal. surfactant. (?)

Will you have a metering valve, like one from Midwest or will you be batch mixing?

You want a lot more water, remember it’s somewhere around 3-4% SH.

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I started out as a roof cleaner. Have at least a 100gal mix tank unless you’re going to have a metering valve. Here are some pics of my first trailer, before the days of metering valves.

Depending on variables figure about 50 sq ft of roof per gal of mix to be safe. I just set up trailer so they could load a drum of SH onto. I think it was a 6 by 10 trailer if I remember. Think I had about 4k in whole setup.
But get a good metering valve if you’re serious about it and think you’ll be fairly busy. It’ll pay for itself fairly quickly.


Yes, I plan on using metering valves / proportioner.

I plan on using a Hudson float valve in the water tank and tapping into the customers garden hose spigot.

25 gallon tank is to small. You have no room to grow. If you have the space definitely put a larger tank. You don’t want to have to fill it to the very top

Thanks Racer - Wow, awesome set-up on all the equipment (electronics and pumps). Mine might not be so elaborate, I’m working on a tight budget but I’ll post some pics once I get it done. This will be a starting point for me eventually moving into a skid in a pickup truck bed.

If I have a 25gal. just for SH, another for water (with a hudson float valve), and a 5 gal for surfactant, do you think I can do at least 2-3 roofs (or more?) before running out of SH?

Not saying its impossible. But NO

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Okay - Thanks. Appreciate your help for sure.

I’d get at least a 50-55 gallon tank for sh if it were me……

How many Roofs with average “black streaks” can you get out of that? (55gal. tank of SH) :thinking:

At least 3 average roofs, I run around 4% majority of the time with metering setup, sometimes higher depending……

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Thanks - Didn’t realize it took so much SH.

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Can take more depending on how bad the roof is and touch ups after but usually not that bad….4% seems good for me in my area majority of the time.


Say you do a 5000 sq ft steep pitch roof that’s pretty bad and using my 50sq ft formula, then that’s a 100 gal of mix at 4% you’re talking close 40 gal of SH for one roof. Depending on SH cost in your area, other than FL, you need to charge enough to make it worthwhile. Your cost of materials with SH, and surfactant could be .10 a sq ft.

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Don’t forget ladders, they’re expensive

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