Ask the Expert Question-and-Answer Archive

by Ron Joseph

October, 2003

Repainting Old Tin Roof

Q. I would like to know the best way to repaint an older tin roof.This particular tin roof was painted about 5 years ago. The paint that was used on it was a benjamin moore floor and deck enamel oil base with urathane.I not sure what primer was used on it.I want to powerwash it and get as much of the old paint off as possible. since it is tin it will rust fast.Please tell me what is the best primer and finish coat that shold be used.

A. After you remove the old paint on the roof and also sand down corroded areas, I suggest that you apply a corrosion resistant primer. It doesn't matter who the paint manufacturer is as they all sell basically the same type of products. If you go to an industrial paint store, as opposed to a retail consumer store, you might be able to get a more corrosion resistant primer. When you refer to a "tin" roof, you are generally speaking about a galvanized (zinc-coated steel) roof. Are you sure that you mean "tin" and not galvanizing? It makes a huge difference.

If it is galvanizing, as I suspect, you need to purchase a primer that is designed to go over zinc. Most oil-based paints, (alkyds) do not perform well on galvanizing. An industrial paint store will be able to give you the appropriate primer. On the other hand if the galvanizing has worn through and you are now painting over steel, then you can use a corrosion resistant oil-based or waterborne alkyd or acrylic primer.

You can apply a high quality roof topcoat over the primer.