Posted 07-20-2004 at 05:48:20
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New galvanized roofs need to weather a year before priming so the paint adheres; I'm guessing the vinegar idea is to speed this along. I don't believe it is needed for an older roof.
I've done 3 metal roofs since I moved to my place, all old. Did two myself, paid somebody to do the barn cuz it is so high. Barn started flaking and rusting in a year; ones the wife and I did ourselves looked good for about 3 years before showing any wear at all and that was minor.
We prepped really well. Washed down the roof, let dry. Used stiff push broom to remove all loose paint and rust. Used a stiff brush to get the stuff that wasn't really loose yet but didn't look like it'd stay for as long as I wanted the paint to last (judgement call)...we did not try to remove every bit of old paint, just the loose or soon-to-be loose stuff.
We painted with the silver roof paint on the thought that it would keep temperatures inside (both buildings are chicken coops) cooler in the summer. We brushed it on, rubbed it well into the seams. The guy that did the barn sprayed, which went much faster but of course didn't last at all.
As I said, we did the coops over 5 years ago now and I don't think they'll need redoing for another 5 years so I'm happy. The guy that did my barn and charged an arm and leg is no longer welcome on my farm.