# Repainting a metal roof



## kdrymer (May 13, 2016)

Hello - I am planning to repaint my metal roof to give my garage a better appearance. As you can see in the pictures there is some minor surface rust covered on a large area of the roof. The material appears to be galvanized steel (attracts magnets). My plan was to (in this order) wire brush the roof first, apply phosphoric acid for any residual rust not removed from wire brushing, then apply a TSP detergent to clean the surface, followed by pressure washing the roof, applying a rust inhibitive primer, then an acrylic exterior paint. Any changes or additions to this process you would recommend? I have seen acrylic paint products labeled as "Direct to Metal (DTM)" that claim they do not require primer application beforehand, however the information I have seen thus far suggests always using a primer even with this type of paint.

The next thing I am struggling with is how to apply the primer and paint. The roof has the channeled profile so I would need to find a special roller that matches the roof profile in order to apply by roller. The other method I considered was renting an airless sprayer, however I must admit I do not really have experience with these so I'm not sure this would be a good situation to learn this skill. Appreciate any feedback, thanks!


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## nealtw (May 13, 2016)

This looks interesting.
[ame]https://www.youtube.com/watch?v=F7Akx5fXq2c[/ame]


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## elbo (May 14, 2016)

I would suggest a coating like  "devcon Z " It has a high amount of zinc in the paint and because of this is quite heavy. It is used by the military for rust protection. I ran across this when I worked for a major airline and we used it to coat the tops of the jetways. rust that had been a problem before, wasn't anymore.This is because if the coating is scratched the zinc migrates over the scratch and protects it again. It applies like paint, but might be a little expensive


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## bud16415 (May 14, 2016)

Your process sounds like it would work well. It also sounds like a lot of work. I would most likely pressure wash it and let it dry good and use a product that says it will cover over rust. I would most likely spray it on. Your spraying skills will improve quickly and it&#8217;s not like you are painting a car.


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## kdrymer (May 16, 2016)

Thanks for the feedback! After going through the preparation process, would it be wise to re-caulk all of the exposed screw heads securing the panels? They appear to have a neoprone type washer attached to seal out water but I'm not sure whether they should have a bead of caulk reapplied after work is done? Any type of sprayer you would recommend for this application?


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## DFBonnett (May 16, 2016)

I've used the previous solvent borne incarnation of this years back painting metal sheds. Worked well, but I also spot primed with rusty metal primer on the bad spots just to be sure. Ben Moore Ultra Spec® HP D.T.M. Acrylic Enamel.
FWIW
YMMV


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## slownsteady (May 17, 2016)

Sprayer is the way to go. Practice on scrap, or even in the center of the roof, where you can cover your mistakes later on.
I have seen rust neutralizer paint in small cans, i would guess it's available for bigger jobs too.


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## kdrymer (May 17, 2016)

Any recommendations on paint sprayers that would work with an acrylic DTM type application? I don't want to spend a lot of money on a sprayer that will very rarely be used. I saw Harbor Freight had several models but it seemed unclear what type of paint their models are compatible with.


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## slownsteady (May 17, 2016)

Any chance a sprayer can be rented?


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## DFBonnett (May 18, 2016)

kdrymer said:


> Any recommendations on paint sprayers that would work with an acrylic DTM type application? I don't want to spend a lot of money on a sprayer that will very rarely be used. I saw Harbor Freight had several models but it seemed unclear what type of paint their models are compatible with.


Local tool rental places should have some airless units. You may have to experiment with different tips to find the right one. When you factor in all the time to acquire, set up, then clean a sprayer for a job this size, it might be about as fast to just do it with a quality 4" brush.
FWIW
YMMV


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## bud16415 (May 18, 2016)

I am not a roofer and only ever painted one steel roof in my life and I remember waiting till the morning dew was off it to start and within an hour it was so hot I couldn&#8217;t stand sitting or kneeling on it and it was too steep to stand up on. and I said never again and replaced it with shingles a couple years later. 

We have a bowling alley close by that they redid the steel roof with an elastomeric paint on coating something like the Henry  or Sta-Kool product. That can be brushed on with a long handle roofing brush or I think a really heavy nap roller. 

Maybe some of the contractors will comment on if these coatings are the right stuff.


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## oldognewtrick (May 18, 2016)

If it were mine, I'd roll it after prep with elastomeric color tinted to the color of your choice. Just my 2 cents.


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## kdrymer (May 23, 2016)

I've searched high and low to find an economical sprayer that is compatible with this type of coating, and the only ones I can find that specifically mention they are DTM compatible are a few hundred dollars. I am starting to think along the lines of DFBonnett and just use apply with a hand brush. I looked at rollers that would match the profile of the roof panels and those are also expensive ($75 for one) so I may need to resort to the tried and true brush technique.


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## nealtw (May 23, 2016)

Have you checked for a rental sprayer.


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## kdrymer (May 24, 2016)

With the uncertainty with what type of sprayers are compatible with this material I did not want to take the chance of damaging rental equipment. Thanks all for the feedback1


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## oldognewtrick (May 24, 2016)

No bigger than that roof is, I'd roll it. It would be faster than setting up the spray rig and cleaning up afterwards. Prep is going to be the same. Get a helper and you'll be done before you know you started.


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## oldognewtrick (May 24, 2016)

Any long knapp roller cover will work fine for what you're doing.


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## kdrymer (May 26, 2016)

Someone I work with recommended this style brush to apply it with that can be pole mounted. Any thoughts?

http://www.homedepot.com/p/6-in-3-Knot-White-Pro-Roof-Brush-THD01803/203737538

I'm also now considering this product, as opposed to a DTM coating. Again, thoughts on this as opposed to the DTM application?

http://www.homedepot.com/p/Henry-4-...PIPHorizontal1_rr-_-203737538-_-100094951-_-N


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## oldognewtrick (May 26, 2016)

I'd stick with s roller. I think it will give you more of a consistent coverage and be a whole lot easier to apply. 

Which ever product you choose follow the MFG's directions for the best performance. And don't take any shortcuts on the prep work. Prep is the key to making any coating last its longest.


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## kdrymer (May 27, 2016)

Thanks I will use a roller. One last question (I hope!)... Does anyone have experience with the Rust-Oleum Clean Metal Primer product? I was planning to apply this primer (after prepping the surface) and then apply Rust-Oleum Protective Enamel, however I'm unsure whether or not the roof is galvanized steel and whether this type of primer would adhere to the surface. I'm hoping the etching with the phosphoric acid will help with adhesion, but I also see that Rust-Oleum makes a primer designed specifically for Aluminum and Galvanized surfaces. Which product do you think I should use? Since you can see light rust on the surface, this leads me to believe it is NOT galvanized, but I have no other way of confirming that. Unfortunately both of these primers only comes in quart sizes so I've been having trouble finding enough of it.

Rust-Oleum Clean Metal Primer:
http://www.homedepot.com/p/Rust-Ole...at-White-Clean-Metal-Primer-7780502/100126115

Rust-Oleum Galvanized/Aluminum Primer:
http://www.homedepot.com/p/Rust-Ole...Preventive-Primer-Case-of-2-8781502/202058550


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## oldognewtrick (May 27, 2016)

I would go to your local Sherman-Williams or Porter Paint store and have them rev omens the primer and top coat. I've always had good results dealing with both. Stay away from the big box stores. The lines they carry are often lesser quality. Just my 2 cents.


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