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Galvalume Metal Roofing

Posted by Jim P. on January 1st, 2000 08:39 PM
In reply to METAL ROOFING by PASCALE on December 14th, 1999 01:42 PM [Go to top of thread]

5 of 5 people found this post helpful

Galvalume is not really paint, but an electro-mechanically bonded coating of 55% aluminum, ~43% zinc and 2% of something else that I can't remember. Bethlehem steel developed it about 30 years ago and the test panels they have had in the field for over 25 years are supposedly still shiny bright. Be sure you don't make the mistake of buying galvanized (100% zinc coated) metal roofing - it has a significant probability of the
zinc coating failing with the unfortunate result of the substrate steel rusting out. As far as the SCREWS with the neoprene washers shielded by a metal washer, they will last a long time before the neoprene would dry out and cause a leak. That's the purpose of the metal washer on top of the neoprene washer - to shield the neoprene from UV radiation (ie. sunlight) which is the culprit as far as Neoprene failures. Be sure not to overtighten the screw and make the neoprene washer bulge out from under the metal washer. If you are overly concerned about the neoprene washers failing, you can buy a fastener called a ZAC screw which has a hex head with a metal dome which completely covers and shield the neoprene washer from sunlight. The downside is that they are very expensive, about 35 cents each versus about 5 cents for the more routinely used screw fasteners. I am currently building a home for my wife and I and decided to install a metal roof with a galvalume finish. I am using the "normal" screw fasteners (not the expensive ZAC fasteners) and feel quite comfortable doing so. I have looked at a number of metal buildings 5 - 10 years old and have not seen any significant deterioration of the washers. The $600 I save by not using ZAC screws (materials cost only - I am building this house myself, without hired labor) will pay for the "insulating paint" I plan to coat the roof with the second year I live in it. The "insulating paint" will further protect the fasteners and the edges of the neoprene washers.
If you don't know about "insulating paint", read about it here:

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