Hey so I see a lot of people talking about galvalum roofs saying that they do not even touch them. But then I also see some people saying that it should clean up no problem and is pretty easy to approach.
I have a school district wanting me to wash six elementary schools roof, so I would like to know if I should quote this job or walk away. Would be the biggest job I’ve ever done so I’d like to do it if possible! Just not sure if the metal roofs will change color/rust or damage in any way. Which would be detrimental to my business.
Full Name (jd-metals.com) I found this procedure on jd-metals.com for cleaning Valspar brand HDG and Galvalume. I’d call JD metals to make sure this process isn’t Valspar-specific, but the way it’s written seems like it would apply to all “coated metal” surfaces. I also found this procedure somewhere on here:
“.05 percent SH “ housewash mix “ will clean most metal roofs
1 percent is generally max for non colored and dark colored metal roofs.
2 percent is max strength and usually only used on commercial roofs and white colored metal roofs.
Hardware the is the real problem.
Always check the hardware first. If the fasteners are galvanized are have been painted to match . I would recommend not cleaning the roof. No matter how much rinsing is done they might still rust. Although they shouldn’t be there since most metal roofs must be installed using coated hardware unfortunately many roofers take the cheaper route.
To determine quality hardware just lightly scratch the fasteners with a wire brush. If its quality the color will not come off.”
There is also a product called “Wash safe Premium Eco-Safe” that is supposedly safe on galvalume, organic, non-toxic, made of sunshine and rainbows, but a 5 gal bucket costs about as much as 55 gals of SH 
Hope any of that helps. I’m curious myself as to what the best practice would be.
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Most decent housewash mix is between .8% and 1.2% SH concentration, not .05%.
yeah I think that was a typo from the original poster, i had just copied and pasted to my word document and forgot to correct it
Really appreciate the detailed responses! I’ll make sure to check him with him as well and see what he recommends best
