Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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How to paint a galvanized metal roof
1 2
June 29, 2009
Q. Hi,
I live in a house built in 1906 but I don't know the age of the metal roof. It is galvanized and although it doesn't leak, it is not pretty to look at because of a lot of rusty areas.
I have some experience with sandblasting and industrial coatings and was thinking of blasting it with a fine 40 mesh sand and painting it was a inorganic zinc coating like Carbo Zinc 11 because 1) I live in Florida and rain won't hurt the zinc coating after only an hour after applying - this will allow me to get the blasting and priming done without too many problems withe the rain and 2) the zinc is cathodic protection like the galvanizing
My questions are: 1)will I need to use anything like TSP before the blasting
and 2) what should I topcoat with - metal with a zinc coating gets hot in the sun and I'm a little worried about that and would like to save some money on my air conditioning bills (not make the bills larger)
Thanks,
David
- WINTER HAVEN, Florida
Q. My father is having the tin roof on my parents old farm house over. its being scraped and primed but what about paints for it. my parents seem to be having a 'discussion' on whether the paint he bought - Rust-Oleum Professional High Performance Enamel Oil-Based will work. Any help would be appreciated!
Stacey B [last name deleted for privacy by Editor]- Village, Virginia
July 24, 2009
A. I have painted many galv roofs; we usually clean it with a roof wash, anything that lifts the grime, and salt. If near the sea, spot-prime with a galv primer, rust-kill any rust, replace any nails, prime these, and then two top coats. If you need a product in NZ, try Reids paints or Dulux
gerry kenna- wellington New Zealand
September 17, 2009
Q. I have a metal rod iron fence that is about 15 yrs. old. It was painted black in the beginning and still is. There are parts of it that was painted with a primer over galvanize, and some that is not. The part that was painted over the galvanize without the primer is beginning to flake. What would be the best way to refinish the fence?
Joe H [last name deleted for privacy by Editor]Maintenance - Mobile, Alabama
March 15, 2010
What a very informative site; excellent.
- London, U.K.
March 20, 2010
Q. My cargo trailer's sheet metal roof has rust patches I think from parking under pine trees. What needs to be done to remove the rust and not have it come back?
Bob S [last name deleted for privacy by Editor]Hobbyist - Howard, Pennsylvania, USA
August 16, 2010
A. What an interesting site this is. I have painted three tin roofs (or is it rooves?), all in Dunedin, South of the South Island.
I am due to do my fourth in our Summer, January 2011. I am pleased to report this is not as steep as others I have done, and I will not need to tie myself on. I should be able to walk on it quite comfortably.
My tip - In the preparation, where it is recommended that you give it a good rub with a wire brush. I have found that chicken wire, squashed into a ball shape, is far better for rubbing down the corrugated iron roof. Much easier, and very efficient.
Happy painting.
- Dunedin. New Zealand
September 6, 2010
Q. Hello
We have a simple tin roof (no paint) on several older buildings where I work and in several places the tin is starting to rust. I want to take the necessary steps that will stop the rust but also just maintain it for future years.
I understand I need to powerwash and scrub the rust but I am uncertain as to what I should apply afterwards. As mentioned, it is unpainted and I would prefer to keep it that way so all the buildings will still match.
Basically, just looking for something that will protect the roof and it keeps the plain tin look. Any help is much appreciated
Thank you
Mosby
- Trinity, Texas, usa
September 27, 2010
A. Roof coating.
We have been in the metal roof restoration business for 15 years. We have found the best way to restore a look similar to the original galvanized color is to use a product from ALCO/NVC. They are out of Detroit MI.
If you are looking to preserve the metal and add color the best products for this application we have found are produced by Truco, Inc. in Cleveland OH.
Over the last 15 years we have restored over 20 million square feet of roof surface and tried many different products, we have found these to be the best.
- Houston Texas USA
January 11, 2011
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Hi, folks! We appreciate everyone taking the time to post their recommendations! But to the extent practical, we prefer responses like: "epoxy is better for this purpose than alkyd", or "oil base offers thus-and-so advantages over latex" -- rather than "Company X in France has a better secret formula than company Y in New Zealand" (which seems to always start a race to the bottom, and is quite unfair to the supporting advertisers who are making this site possible for us all). Thanks! Regards,  Ted Mooney, P.E. Striving to live Aloha finishing.com - Pine Beach, New Jersey January 12, 2011 |
A. I am a qualified roof painter and also do restoration to properties in n.z. If you have a waterblaster which is round about 3000 psi it should be sufficient to remove all dirt, lichen, mould and residue. loose paint may need removing with a hand tool till it is at a point in which old paint is well bonded to the roof metal. scrape and sand rust prime with solvent based product to just the affected areas. if your roof is galvanised iron/metal you only need to prime it with metal primer if it is less then 1 yr old otherwise the weathering process will do the job for you. Once all this is complete then you can apply two coats of acrylic paint in any desired colour, if done properly it should last 10 years no prob. I recommend a spray finish as it saves a truck load of time and has a pro finish!
krish clayton- Hamilton, New Zealand
March 3, 2011
A. FOR RUST ON ANY METAL I HAVE BEEN USING A PRODUCT CALLED Por-15 Rust Preventative Coating ⇦ this on eBay or Amazon [affil links] . IT IS EASY TO USE BUT FOLLOW THE INSTRUCTIONS. ONCE DRIED ON YOUR SKIN IT IS THERE UNTIL IT WEARS OFF.
ED MORRISSEY- SANTA ROSA BCH. FLORIDA USA
May 25, 2011
Q. We recently acquired a cottage in Canada with a white metal roof which we want to paint a different color. It shows no rust and needs only power washing. Our question, do we need to etch the present surface so the sprayed paint/primer will adhere properly? Or just spray on a primer direct then spray with 2 coats of finish?
Jake C [last name deleted for privacy by Editor]- Traverse City, Michigan
June 16, 2011
Hi, Jake -- sorry but I'm a little lost.
If this is a galvanized roof that an owner has previously painted white, and he has secured good adhesion to it, I would not mess with that. Getting adhesion to previously applied paint is usually much easier than starting back at the metal again, and there is good advice on this page from professional painters and successful do-it-yourselfers about that.
But if you are referring to a baked enamel "factory painted" roof rather than an owner-painted galvanized roof, that's a somewhat different thing. Good luck.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
June 16, 2011
Thanks Ted
Our roof is less than 20 years old and is a "factory painted" metal roof. We simply want to change the color.
- Traverse City Michigan
June 17, 2011
Hi, Jake.
What I am suggesting is that the article that describes repainting factory-painted aluminum siding should be applicable to repainting a factory-painted roof. What you are painting is the existing paint, not the underlying metal. Good luck.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
June 20, 2011
A. Painting galvanized metal is tricky; etching is absolute. What to etch with is tough (EPA regs, surrounding area, safety, etc.) As far as pressure washing, just a garden hose and dawn soap removes old gunk the best. I wet sand with a large disk hand sander from sherwin williams while I wash the roof after it's dry. Old galvanized metal still needs etch. I used lacquer thinner ⇦ this on eBay or Amazon [affil links] Warning! highly flammable! . My paint choice has and always will be Benny Moore IRON CLAD it can be gotten in every color except 4-b dark colors. Spreading rate says 4 to 5 hundred but plan on 250 square feet per gallon. no priming. this will last 5 to 7 years. Do a second coat after 2 years and it will out live you! Brush and roll. be careful on your roofs. signed Rusty
Rusty McIntyre- Wilder Vermont United States
July 14, 2011
Q. I read on a different website that the krylon H2O spray paint will work on galvanized metal. Is this true?
Angela M [last name deleted for privacy by Editor]- Rio Rancho, New Mexico, USA
August 18, 2011
A. Hi, Angela.
I haven't tried it and don't know, but would be surprised. As far as I know, it's just latex paint in a spray can. I don't know why putting latex paint into a spray was more difficult to do than brush formulations for latex paint, but apparently it is a recently solved challenge.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
August 19, 2011
Q. I sanded, scraped and put my first coat of paint on the galvanized roof of my 105 year old house. Do I need to do a light sanding between the first and second coats?
Alison H [last name deleted for privacy by Editor]- Afton, Virginia, USA
November 9, 2011
Q. How do you go about painting galvanized metal and what kind of paint would you use?
John s [last name deleted for privacy by Editor]painting contractor - Houma, Louisiana usa
November 10, 2011
A. Hi, John.
We appended your inquiry to a previous thread that discussed the same issue. Pick one of the pretreatment ideas and be sure to avoid alkyd paints. Good luck.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
November 10, 2011
Q. Hi, I have read the above info about pretreatment and preparation. My question is does all this apply to Quonset huts? I will be doing mine this summer which has been previously painted and it now has peeling paint and some rust. I am trying to find the best overall solution for resurfacing it. I am looking for a product that will keep the roof cool as well as giving it a long term coating. Is it better to spray or roll the paint on? Thanks very much in advance to anyone who can assist.
John
- Ottawa, Ontario, Canada
April 10, 2012
Q. Re. etching! If I was to use household vinegar ⇦in bulk on eBay or Amazon [affil links] to etch my galvanised iron roof as part of the prep, do I use it neat/on-the-rocks or mix with a carrier, i.e., water. If so, at what ratio? If I choose to use TSP, same question. Many thanks. Mark :-)
Mark Lyons- New Zealand
June 7, 2012
A. Hi Mark. I've never heard anyone claim that the vinegar dilution ratio was critical, so I'd go 50:50 with water. If the vinegar is still too strong smelling or too expensive, it probably wouldn't hurt to cut it 50:50 a second time.
TSP is not an etch, it's a cleaner, a powdered detergent, and the suggested strength may be on the box. If not, a cup in a gallon of water would probably be a strong mix. TSP, if used, should be applied before the vinegar.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
June 7, 2012
Q. I have some knowledge & experience in the prepping phases, i.e., washing, priming, etc. What I need to know is what about all those asphalt coated screw heads and seams?
Do I need to strip all of this off, replacing nails or screws? What sealant type paint may be used, and are there colors other than black and white? My roof is old rusted galvanized on a 200 year old cabin. No telling how old the metal is but it does keep us dry.
- Sunset, South Carolina USA
September 26, 2012
Q. I have a historical 60 ft. high 40 x 90, 2-pitch 1930 galvanized steel roof, never been painted, mostly covered with rust. QUESTION: Is there a method/product that will last more than 20 years?
Lynn Johnston- Debert, N.S., Canada
December 8, 2013
A. D.T.M. (Direct To Metal) Paint ... NO PRIMER NEEDED ... ONE COAT ONLY ... Most colors are available (green, red, etc.)
Bradley Busler- Statesville, North Carolina, USA
February 26, 2016
Q. I'm painting a galvanized roof on a house that I have painted every ten years (40) since it was painted several times before. I'm now seeing colors I've have never seen before. Last time it was pressure washed, scraped, wired brushed, primed with metal primer and painted using Devoe Paint. I'm 6 years down the road and looking for a longer life as the pant is peeling. Suggestion are welcome. Thanks.
Mike Jones- Vinton, Virginia
March 24, 2017
Q. We have a galvanized steel quonset building that is new. Wanting to get a stain/color like weathered copper/greenish on it. Would like more of a translucent appearance than a thick color coat. Suggestions for a product & application for this please. Thank you in advance.
Bonnie Farrell- Salida, Colorado, USA
April 11, 2017
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