Reaction With Pressure Treated Cedar Roof Shingles

Kenneth Holzberg
2/18/2011
I have a galvalume roof on my one-story wrap around porch. Above it, on the second story roof, my contractor installed pressure treated cedar shingles. With the first rain, the galvalume roof immediately appeared to rust/corrode from chemicals leeching from the cedar shingles. It continues to worsen. Is there any way to remove this corrosion? My contractor wants to try a product called CLR, but I'm concerned that such a strong chemical will cause further damage to the galvalume. Is there any way to prevent further damage from the leeching? There is a gutter on the second story roof, but it is ineffective as a barrier in the winter months when it is filled with ice and snow; when the snow is thawing, the runoff just bypasses the gutter.
Todd Miller
Isaiah Industries, Inc.
3/3/2011
There probably is no way to stop this. It will lessen over time but the damage will be done. I think that CLR will create additional damage. A quality paint system on the galvalume roof would be one option. You could even stay with the silver or mill finish sort of color.
Eric Novotny
An informed customer is the Best Customer!
3/3/2011
+1 The CLR is designed to remove oxidation and mineral content via a chemical interaction. It is likely that this chemical would further strip the roof of any protective finish.
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