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TOPIC: I Have An Existing Metal Roof and Have A Question

rust flakes from grinder on new roof

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I have just had a new galvalume roof installed on my house. The contractor got the ends crooked down one side of the house so he cuts the whole side off with a grinder. Now I have small rust spects all over the roof, heavy in spots scattered in others. How much will this harm the roof if nonthing is done. Will a pressure washer wash them off ? I have read the old post that I could find on the subject. Soft scrub was mentioned. How is it applied and used? Thanks
Charles Nichols

11/27/2015
You need to get rid of those. Otherwise the rust will work its way through the paint finish and reach the base steel. Soft scrub would have to be used by gentle hand scrubbing. Take care to not damage the paint. I do not think power washing will remove the metal shards though you can try.
Todd Miller
Isaiah Industries, Inc.

11/27/2015
In order to remove iron filings from the installed Mill Finished Galvalume product, you should clean the surface using a mild household cleaner such as “Soft Scrub” and a wet soft sponge. This will help remove the small stains that appear from the iron filings. The cleaned/treated area will have a different appearance than the uncleaned areas. The roof will eventually weather making it look more consistent in appearance. Low Pressure washing can also be considered (2500 psi MAX), a little elbow grease and a standard hose to rinse the residue off of the rood should get the job done for you. As always...please make sure to use proper safety harnesses to avoid falling off your roof. Happy Holidays!
Brian Partyka
Metal Roofing On-Demand

11/29/2015
Thanks guys for the replies. The roof is over 2500 sq ft and to hand wash every sq ft would be quite a job. Most of the pressure washers are going to be about 3500 psi. Do you think that would harm the roof? I think that would knock the shavings off. The roof is high and you cannot see the spots anywhere from the ground so I am not very worried about the cosmetic appearance. I just want the roof to not be damaged by the shavings. Thanks
Charles Nichols

11/30/2015
Charles, do you know what sort of paint finish / coating is on the roof?
Todd Miller
Isaiah Industries, Inc.

11/30/2015
The roof is not painted, it has the galvanized coating going by the name galvalume. It has a 25 year warranty.
Guest User

12/1/2015
Charles, the warranty you are referring to is an assurance that the flat part of the metal will not rust through. The bends, cut area or scratches are excluded. I doubt the grinder dust will be a problem as it is 'burned' into the acrylic coating. If you can live the aesthetic issue, I would leave it alone.
Dick Bus

12/1/2015

I just had my white metal roof installed less than a month ago. We love it. Got on the roof to clean some debris and discovered what seems rust specs all over the roof, at different locations and different intensity. Can anyone please advise? Most grateful.
Here are some pics.image0.jpegimage1.jpegimage2.jpegimage1 (1).jpeg
Al Moreno

10/29/2020

This looks like perhaps they saw cut panel ends and had hot shards of metal land on the panel surface and probably melt into the paint a bit. This is not something I like to see. Panel ends should not be saw cut on steel panels. I suggest contacting the contractor and manufacturer right away. It might be possible to clean this off with Soft Scrub or something but if it has melted through the paint and reached the steel beneath, I fear the rust will spread. I am very sorry.
Todd Miller
Isaiah Industries, Inc.

10/29/2020

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