Metal Roofing Gauge

November 23, 2009 | Filed under: Metal Roofing Gauge, Misc

Q: I am looking at samples of several roofing products. Two of them claim to be 26 gauge, but they feel very different. One is clearly lighter than the other. Can I use a micrometer to test the thickness and figure out which one really is 26 gauge? Is there a chart that would tell me the appropriate thickness for the 29, 26 and 24 gauge of roofing materials? Please review and advise. This is very important to me.

A: As long as you gauge a flat area of metal, sure you can check it with micrometers. I have long been a proponent of the industry looking at steel roofing in terms of decimal thickness rather than gauge.

Too many games can be played with metal roofing gauge in regards to tolerances, with paint, without paint, etc.

You can find charts referencing gauge and decimal thickness but as you will see there is a wide range of tolerance on decimal thickness for each gauge.

todd Miller

has spent his entire career in the metal building products manufacturing industry. He is president of Isaiah Industries, an organization recognized as one of the world’s leading metal roofing manufacturers. Todd is currently Vice President of the MRA (Metal Roofing Association) and a Past Chair of MCA (Metal Construction Association). Through his website, he strives to raise the bar on standards and practices to provide property owners with the best possible products for successful roofing projects.

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74 responses to “Metal Roofing Gauge”

  1. Andre Leamy says:

    What is “oil canning” ? I was asked to sign a waiver if I installed a 24 ga smooth flat standing seam roof. Thanks

    • toddmiller says:

      Great question Andre. Thank you.

      Oilcanning refers to ripples which can appear in the surface of the panels. Most common causes are inherent and unavoidable stresses in the shape of the metal, and imperfections in the flatness of the surface being installed on. Other causes can be improper panel formation and improper installation.

      Requiring this disclaimer is not uncommon.

      You may wish to ask the contractor if they have any options for ribs or striations in the panel which can help to mask the appearance of oilcanning.

  2. Teresa Faulkenberry says:

    I currently have a shingle roofed one story house in full sun in North FL. I am NOT on the coast, about 8 miles from the GA line.

    I have two different metal roofing quotes.

    First Quote-24 guage galvalume w/ a kynar 500 painted finish, metal standing seam roof system with 1.5″ risers, 1″ expanded polystyrene foam insulation underlayment, concealed fasteners, boots and vented ridge. This quote is double the cost of a shingle roof.

    Second Quote-26 guage Versa-Lock metal roof system over titanium underlayment. There is no polystyrene insulation. This quote is only about 25% higher than the shingle roof.

    My questions–
    How much does the guage of metal matter? Is 26 guage (a lighter metal) inadequate?

    Also, how important is the poly insulation? Should I definitely get it or just add additional attic insulation?

    I appreciate any help you can give me!!


    • toddmiller says:

      These are good questions. I would suggest a concealed fastener panel and these both may be that. I would also suggest a quality coating such as Kynar 500.

      Generally I am not real fond of foam beneath systems and would prefer to see attic ventilation and insulation on the attic floor but some construction does not allow for that.

      I would look for what wind uplift ratings they have. Heavier gauge doe snot automatically mean better performance. Product design and installation have great bearing as well.

  3. Benjamin says:

    Have you heard of metal roofing over existing asphalt shingles with airway in between for venting. Is this do-able and what is your thoughts on it? Thank you for your comments.

    • toddmiller says:

      There are various ways to do this depending upon the particular metal roof being installed and depending upon construction methods. Generally, I see this as a way to increase energy efficiency and decrease the possibility of ice damming. It can also be helpful with avoiding condensation issues in certain cases.

      Every job must be looked at individually to determine whether this is worth the cost. Additionally, some products such as the metal shingles have integral airspaces to act as a thermal break and help with energy efficiency. Energy efficiency is also boosted by coatings with reflective pigments.

      If anyone wants to call me at 1-800-543-8938 ext 201 I am happy to discuss your exact roofing situation and make a recommendation as to what would be best for you.

  4. Floyd Rogers says:

    I was on the site and decided to contact you to ask a question. I needed to know if you could advise me about the exact thickness of galvalume metal roofing metal as to how thick 26 gauge is with the substrate and painted process combined. Is the metal .018 normally before any substrate or paint has been applied and if so then what is the thickness after the paint and applications on the metal combined? I ordered some 40 year galvalume but it only showed .018 thick totally. I felt it should have been thicker due to the layered paint on 26 gauge metal which is supposed to be .018 thick without any additions to the bare metal? Let me know if you will. Best regards, Floyd Rogers 7317074249
    P.S. Your secretary did not know what galvalume was when i asked about this.

    • toddmiller says:

      Floyd, that is a great question. One of my frustrations with the steel industry is the lack of clarity surrounding this. I call it the “gauge game”. I have lobbied for years to now avail that steel begin to be referenced in decimal thickness like other metals rather than in gauge which has wide variances and can be subject to individual interpretation. Frankly, if today you are getting 26 gauge that is micing out at .018″ with paint, you’re doing well. In most cases, yes, gauge refers to the thickness with coatings. Thanks much for your question. All Best.

  5. Floyd Rogers says:

    Well, I see that you agree that metal at 26 gauge is .018 with coatings. I assume the coating must be microscopic then?

    • toddmiller says:

      Yes, in a typical Kynar 500 or Hylar 5000 coating, there will be a primer that is approximately 0.00015 to 0.00025″ thick and a top coat that ranges from 0.0007 to 0.0009″ thick.

  6. Floyd Rogers says:

    I found this site that was very informative. It explains the U.S. standard for gauge and decimal equivalents for sheet steel, galvanized steel, aluminum, galvanized alloy coated, and of course the cold rolled. Sheet steel is .0188, galvanized is .022, aluminum is .0159, galvanized alloy is .0217, cold rolled is .0179 this being sheet and coil. Now, with the added substrate one may assume that .0188 sheet steel coated with zinc and aluminum should read at least .0217 with no layered protection to the bare metal. The increase in decimal should be greater than .0217. I just bought 26 gauge galvalume which read out to be .0185 at the dealer’s yard and this had been painted with a 40 year paint. I sent a sample to the supplier and had it checked for paint and thickness. The only reply i got in return from the supplier where i bought 1200 dollars worthof 40 year galalume was that the metal checked out to be .021. I replied for an answer to why they had advertised that their metal was 6 percent thicker than other competitors and not to mention how thick my layers of protection amounted to and I got no reply from C.S. Now, i am stuck with having to have the metal lab tested in order to know if i really got what i paid for. I do know that the same company offers a 10 year paint warranty, so other than having a lab test it how am i to know what i really got? I feel cheated now since i could not get an accurate reply or even a reply to their advertisement. Now, i wonder whom i can trust in the metal roofing selling business.

    • toddmiller says:

      Thanks Floyd. I agree that folks need to be truthful. And, as I have stated before, I truly wish the steel industry would switch toward decimal thickness rather than gauge. That said, there are variances coming out of the mills unfortunately. With the speeds at which metal is made, there will be variances even within an individual coil. Industry tolerances allow this because with current technology it is impossible. I will also say that in terms of metal roofing system performance, the following items are what I feel are most important, from most to least important:

      Installation quality
      Panel design (and adherence to that design)
      Coating quality
      Metal type
      Metal thickness

  7. Floyd Rogers says:

    I would like to add another site to show an advertisement from a metal supplier which is considered to be a very faithful and trustworthy company adhering to their worth or word. They state their metal is thicker than any competitors. Here is the site:

  8. Burhman says:

    Is it worth the trouble to install vertical lathing before horizontal lathing over deck?

    • toddmiller says:

      It can significantly help to keep heat out of the attic. If you live in a very warm climate, I’d say it is worth it, particularly if the home does not have really good ventilation inside of the attic.

  9. Paul Oglesby says:

    Todd, we are so confused on all the metals out there. We live in Kentucky and we’d like to get a metal roof, but, very reluctant to rely on ppl here. Quotes are so very different from each. In our working life both my wife and I were buyers, so, needless to say we’ve quoted the material at several places and they too differ so.

    We were told by our insurance company that we would need 37 squares. Some of the contractors told us we’d need to remove the two layers of composition shingles and some said just one layer (yet another told us when you remove the top layer you’re going to mess up the bottom layer, is this true?), while others said we don’t need to remove any, just place metal over it all. Then some said, doesn’t need fir’g strips while others said we do, and, we’ll need the felt as well……HELP PLEASE.

    Do you know anyone in western Kentucky that we can trust to not who-do us? Or do you travel, lol?

    Only companies locally are Lowes (they suggest ExSel Porta/Grace, Menards is ProRib and Coles is Mack Metal…all to be 29 ga but like Floyd, don’t know the thickness or which mfgr is better than the other???? HELP AGAIN PLZ

    • toddmiller says:

      Thanks for the note, Paul. It indeed can be very confusing. Also, metal roofing has grown so fast that all kinds of contractors, qualified and caring or not, have jumped on the band wagon. That is why I run this website … to try to deliver accurate information and be of help whenever I can.

      As far as tear-off, I am generally a believer in going over old shingles when you can. I see it as increasing the home’s thermal mass for energy efficiency. It also saves our landfills and allows homeowners to spend their money on a better roof instead of labor to remove and dispose of their old one.

      That said, the International Building Code calls for no more than two layers of roofing. If you’re in an area subject to building codes, this will be something you need to consider. Sometimes building inspectors have waived the two roof maximum to allow a metal roof to be installed over the old roof. The low weight of metal roofing encourages this.

      Now, all that said, if you’re considering a through-fastened style of metal roof or one of the shingle-type metal roofs, they are very forgiving for going over the old shingles. Standing seam, though, I feel less good about as its appearance can be affected by an uneven surface being beneath it.

      I have rarely known anyone to remove just one layer of a two layer roof. Its just isn’t worth the bother. If you’re up there removing shingles, you may as well remove both layers.

      Your insurance company likely will want the old roof layers removed. Have you asked them about that?

      As far as furring strips … very few metal roofs MUST be installed over furring strips. Some can be installed over them or direct to deck. And others must be installed direct to deck. So, much depends upon what type of metal roof you’re installing.

      I know this is all confusing. I’d love to discuss it with you on the phone … 1-800-543-8938 ext 201

      Now, interestingly, my company does have an operation in Kentucky. Whereas normally we are a manufacturer only and do not install roofs, we do have one “retail” operation and it’s based in Louisville. This operation sells and installs our metal roofs which can be seen at

      The Kentucky operation is called Classic Metal Roofing of Kentuckiana. They cover the entire state and it is managed by Joe Knife who has been a member of our team for nearly 20 years. Their website is

      If you’d like to talk to Joe, feel free to contact him or call me. At the very least, he may have some ideas as far as who the better contractors are in your area.

      Oh, one more thing … regardless of whether you remove the old shingles or keep them and regardless of battens or not, be sure to install a layer of underlayment prior to the roof. It is inexpensive but very wise and, to my interpretation, required by code.

      Thanks so much.

      As long as you have a well vented attic, though, I do not feel that furring strips add real value and fact is they can create a less secure roof.

  10. roofing quotes says:

    I was is there a difference between a 24 and 26 gauge? I’m planning to nuy a new gauge and didn’t know what is the best gauge to buy.

    • toddmiller says:

      24 gauge should be heavier than 26. However, so many other factors go into determining quality — things like paint finish, product design and engineering (including things like concealed vs exposed fasteners, and uplift resistance), and proper installation. While metal thickness may be one consideration, it is not the only one and perhaps not even a real major one.

  11. Arthur Bleakley says:

    Todd, We are about to have a 24 gauge metal roof installed on our home. Somemone told my wife they had a friend with a metal roof that had encountered problems with using their cell phone after it was installed. Have you heard of metal roofs being a problem for reception with cell phones?

    • toddmiller says:

      On very rare occasion I have run into this. Think about it — we use our cell phones regularly in buildings with metal roofs. WalMart is a great example.

      However, if the home is located in an area where reception is poor to begin with, yes, the metal roof could be the tipping point for a worse situation. I personally have never encountered it though.

      I do understand there are boosters you can put in a building to help alleviate this if it does occur.

  12. Bob K says:

    I have had my 10 x 26 corrugated roof blow of an outer building (it flew like a kite as it hit the house, lol). The adjuster figured 29 gauge corr. metal while all I see at the stores is 26 gauge. Is 26 gauge thicker than 29 gauge or what? Which is best or more costly? (10 ft panels)

    • toddmiller says:

      26 gauge is heavier than 29 and this will normally be more costly. However, other major factors include the quality / type of the base metal, the quality of coatings, and the level of skill of the installer.

  13. Kathy says:

    Hi Todd,
    We are having a home built and want a metal roof. It’s a two story over a basement and garage. It is also sits up on a ridge. We are looking at 26 gauge, Kynar 500, standing seem with concealed clips/fasteners. The entire top floor is the master suite and has attic space over the back half, but a 9ft tray ceiling in the actual 24X18 bedroom area. We love the sound of rain and are wondering what the best method is, without sacrificing insulation or structual integrity.
    Also, do you know any companies,suppiers and/or installers, in the Rockbridge County Virginia area (Lexington 24450), that you would trust to refer us to? We have received so much conflicting information, lack of specifics and pricing all over the place.
    Thank you for your time and any information. Kathy

    • toddmiller says:

      Unfortunately today’s construction methods really do lessen the ability for sound to transmit. Eliminating insulation would be your best way to do that but that does put you at some risk of condensation in the attic and of course makes your home less energy efficiency. If you do go that route I would suggest making sure you have a good vapor barrier behind your drywall to prevent moisture migration from the living space into the attic. That will help avoid condensation.

      Unfortunately i do not know any good installers in your area. There are some manufacturers near you who may have some good ideas. ATAS International, Fabral, and Englert all come to mind.

      Thanks so much and good luck.

  14. Diane says:

    Hi Todd, What is your opinion of Midwest Manufacturing steel roofing?
    .018 nominal thickness after painting

    G100 galvanized coating plus zinc phosphate

    Lifetime paint film integrity warranty
    My hubby thought we needed 24 guage but it sounds like the most important thing is installation and we do have a great installer. Is this good enough for our IL home? Thanks

    • toddmiller says:

      Diane, proper installation is critical. I would need to know which Midwest panel you’re looking at in order to yield an opinion. I am a fan of concealed fastened products and also PVDF (Kynar) coatings. I believe Midwest uses a super polyester coating which is a good finish as well — not as good as Kynar but still better than other available coatings.

  15. Kelvin Phillips says:

    I came across your site while looking for information on ga. thickness. I was pleased to fine there is someone who feels strongly that metal roofing/siding should be advertised as a decimal thickness.We have been in the business of selling metal roofing for years and we [my son and I] are constantly frustrated by having to explain why the 3 brands we sell are “thicker” than several competitors in the area. On the other hand many people do not take time to research and check out crosscut samples from an actual panel and they will say that all metal roofing is the same.We have always stressed quality by only selling those companies with guality thickness, paint systems and excellent trim among other things. Is there anything we can do to influence the industry to change to a decimal measure?It would benefit the seller of top quality metal and the customers. Thanks, Kelvin @ KP Steel

    • toddmiller says:

      Kevin, great to hear from you. I wish I knew how to change this in the industry … I have tried but never gotten very far. Many people like to hide behind the gauge game.

  16. James says:

    My wife and I were given a total bid by a roofing company and a contract was signed. The company has been in business for over 30 years. One week before the work was suppose to start he called to say he quoted me the wrong price and the price went up $3,400. The original price was $8,500. Quite a jump! Does this sort of thing happen and should I be concerned.

    • toddmiller says:

      James, I would be concerned, especially if he did not have any specific reasons to justify the increase. If he simply mis-quoted, that seams like a pretty lame mistake and indicates he does not know his job real well. Keep in mind that at this point he has broken his contract with you. If you wish to go a different direction, you can.

  17. mark petersen says:

    Hi Todd, great forum for those of us researching metal VS other roofing systems. We have purchased a home in northern WI that is susceptible to high snow loads and in this location mold also due to low sunlight exposure on roof. I hope metal will solve both issues. Also, the living room is cathedral design and we are concerned that we may be driven from the room in rainstorm due to noise. Should we leave asphalt shingles and go over the top with metal to eliminate some noise and increase efficiency?, and should we use firing strips and some sort of rigid insulation to reduce noise in this room? Looking forward to your advice, thanks again

    • toddmiller says:

      Good questions. I assume when you refer to mold you’re referring to black streaks on the roof? In many cases that is actually a form of algae, believe it or not. Metal roofs are resistant to that and for the best resistance, I’d suggest a metal roof with a Kynar 500 / Hylar 5000 finish as the molecular bond of the finish is very tight.

      One thing to keep in mind though — in wooded areas, tree sap that lands on the roof and sticks to it can hold dirt and even support biological growth. It can be cleaned and is not usually causing any significant harm.

      I do suggest leaving the old shingles as long as your new roof is appropriate for that. Leaving the old shingles actually increases thermal mass and overall R Value of the roofing system.

      Adding insulation would help with noise reduction. An added airgap from battens (if your product can be installed over battens) or from a cold roof assemble will also be helpful. I have to say, though, over the years, I have heard very few noise complaints about metal roofs. Many folks put skylights in their homes and those are far noisier in a rain storm than a metal roof is.

      An independent metal roofing specialist for your area who I have worked with a really like is

      Good luck and feel free to contact me anytime. My direct email is

  18. John says:

    Is double sprayed enamel a sufficient coating in Southern Calif?
    I am concerned that a regular enamel costing on 26 gauge galvanized sheet metal roofing is an improper application. I believe it will blister in a very-short time. Should I expect this type of coating to be okay?

    • toddmiller says:

      John, this is a good question but I am not sure how to answer it. Feel free to give me more information. Sprayed enamel is not a normal metal roofing coating. Most painted metal roofs have a finish that was applied by roll process when the metal was still in coil form. The common grades of paint coatings available on painted metal roofs in the US, in order of perceived quality from bottom to top, are polyester, super polyester, and PVDF (Kynar 500, Hylar 5000). I hope this helps but feel free to respond.

  19. Trudy Wright says:

    We are researching quality/price information for a garage with a metal roof in the Florida Panhandle. One dealer uses a Tuff Rib or R-Panel with Siliconized polyester coating metal using Valspar paint. It is to have a lifetime warranty against rust & corrosion and is available in 29 or 26 gauge. After reading your answers to all the questions on you site here I don’t find that coating referenced at all and I also don’t know which type of panel would have better wind resistance. (We have a metal roof with exposed screws on our home here and had problems with leaks within 3 yrs of installation, we’re located about 1-1/2 blocks from the Gulf so rust is a major issue here. Our other home 100 mi. north of here has a standing seam roof with no exposed fasteners over a shingle roof and polystyrene panels, we’ve had no problems with it in over 18 years, looks good as new while the one here faded within 3 years……). Could you give me your opinion and recommendation as to the two options a available from this dealer? Thank you for your time.

    • toddmiller says:

      Thanks so much. For applications close to the coat, it is very unusual to find a rust proof warranty on steel products. You may want to double check that.

      Through (exposed) fastened products do very well in uplift tests. There is no doubt about that. But they have the risk of the exposed fasteners Sounds like you have already experienced issues with those.

      Ultimately heavier gauge will perform better. But, proper installation trumps all.

      The polyester finish you mentioned is not the best available. The best available finishes are PVDF chemistry sold under the names of Kynar and Hylar.

  20. ed kratochvila says:

    In reference to the Val spar coated steel exposed fastener 29 mil roof.Should I assume that this type of metal roofing is the bottom end of metal roofing.I live in south west pennsylvania and was thinking of going with this type roofing on a gambrel style roof.The quote i got was to go over existing shingle roof after replacing rotted wood on high section of roof.Any advice would be greatly helpful.

  21. ed kratochvila says:

    The quote was for 4900 for 24 square roof which seemed to good to be true.I looked at another job he did and it looked good from the street.For 4900 he is going to do the house a porch and detached garage.Install 1×4’s every 2 feet.Metal secured with screws.ridge vented.Replace rotted wood on high part of roof.Repair side roof in area visible .Install vapor barrier under metal.New flashing around chimney.drip edge and all trim installed as usual..What should I ask the metal supplier he gave me, Hill Top Roofing Supply.I’m thinking he gets seconds from another supplier.

    • toddmiller says:

      Hi Ed, Of course I have no idea of the size of your home, porch, or garage but that does sound very low cost. I would ask what warranties you are getting covering materials and also covering labor. Ask for written copies of both, and make sure you know who is issuing the warranties.

  22. ed kratochvila says:

    Update I called Roy and and asked about the gauge of metal its 29mil screwed down with screws and washers.i asked what 26 mil would be he said another 800.00.He also said they’ve using something new for about a year.Were as the screw is stainless with a non exposed washer with a cap on the screw head that will match the color.That’s another 165.00 I might just go with the screw upgrade and not the thickness.I thought maybe the weight would be greater with 26 mil
    .As far warranty he said the panels should last 40 years .I’m skeptical but I might go for it.What do you think about the thicker metal.As always thanks for your expertise.

    • toddmiller says:

      The thicker metal will “hold its own” better when the panels expand and contract with temperature. The “holding its own” means it will be longer before the screw holes wallow out and water could get in there. One option at that time is to replace the screws with larger screws. I like the new screw they mentioned — good choice. I would opt for those over the thicker metal but I personally would try to spring for the thicker metal as well. That said, many 29 gauge roofs are out there and performing.

  23. David says:

    Building on the Rappahannock River in Virginia….salt water but not like the ocean…will Advantage Lok II from Union Corrugating be sufficient? It is 26 gauge. Would you do Unpainted Galvalume or painted? Striations? Thanks!

    • toddmiller says:

      Thanks for your question and good luck with your new home. A painted product will have greater rust protection than will an mill finish or clear coated product in galvalume. In any event I would suggest minimum AZ50 or 55 quality galvalume. In most cases, any installations of steel roofing within one mile of a slate or brackish water body will not carry any warranty for rust or finish. Have you considered aluminum at all?

  24. David says:

    Thanks! Is aluminum a lot more expensive?
    What is good brand of aluminum?
    And would you do striations?

    • toddmiller says:

      With recent increases in the cost of steel, the gap is narrowing. Also, one option is to look at aluminum shingles which, because of their forming and shape, can be produced from thinner metals and yet still be plenty strong for roofing and wind resistance. Aluminum shingles are less costly than aluminum standing seam as a result.

  25. David says:

    Thank you very much!

  26. Brian says:

    Hi Todd!
    I’m thinking about a metal roof for my manufactured home. It’s only a 2:12 pitch. However the panel length will only be about 14 feet or less. Looking at the snap lock 3/4 inch high pro snap from midwest manufacturing. The 2:12 is less than recommended for the product. However one person that I talked with at midwest thought that it would probably be ok due to the relatively short panel length. The shorter the panel the less water will accumulate. I’m going to strip off the old junk shingles and put deck armour overlapped on the 3/8 plywood deck. Do think that I will have an issue with water siphoning over the 3/4 inch rib height? Or do you think I’m probably ok due to relatively short panel length. I’m in north central kansas.


    • toddmiller says:

      Thanks much. First of all, I would never suggest using a panel at less than recommended pitch. Make sure the recommended minimum pitch is in writing from the manufacturer. Generally speaking for roofs under 3:12 I suggest a mechanically seamed standing seam but, yes, panel lengths can play into that as well. That said, for a 2:12 pitch, I’d feel comfortable with a snap lock panel only if the seams are at least 1.75″ tall. And, if the rafter lengths are long (yours are not) I would also suggest sealant in the seams. I hope this helps. Please contact me anytime. I can be emailed at

  27. Brian says:

    Thank you for your time and responding Todd. The taller ribbed snap lock products are going to be over my budget I think. I might instead opt for a 36 inch wide panel system. These can be used on lower slopes according to midwest manufacturing. My dilemma with this system is the fact that most of the screws will be going into the deck rather than my rafters. My deck is only 3/8 plywood. This would seem to lack holding power. If my deck is ok structurally, would it be helpful to add another layer of 3/8 plywood over it, thus giving me about 3/4 inches of thickness for holding power on the screws?

    Thanks again

    • toddmiller says:

      There would not be a problem adding another layer of decking. It might be acceptable to the panel manufacturer to add battens over the current deck, fastened into the rafters, and then fasten the roofing to the battens. That said, if you use a quality screw, I am not sure that 3/8″ decking would cause a problem if it’s in good condition.

  28. Jeanine says:

    Todd, kudos to you for this website and for taking the time to respond to people. I’m in the northern Palm Beach County, FL area. The quotes I’ve received for a metal roof range from $24k to $43k – such a large disparity! My question: Have you recommendations for roofing installers or manufacturers in my area? Your time is greatly appreciated!

  29. Barbara says:

    Todd, I live in Florida and I’m a 65 year old widow. Been talking to roofers about a metal roof over one layer of shingles. I chose a 26 gauge product referred to as “Tuff-Rib” manufactured by Baker Metal Works. My roofer believes it would be better to install 29 gauge over the shingles because of the lighter weight. I thought the 26 gauge would be better for hurricane areas. Florida requires 1×4 purlins over shingles plus sealant.

    • toddmiller says:

      The difference between 26 and 29 gauge in terms of weight is minimal. Both products qualify as very low weight roofs. I would go with the higher gauge. I would also look for a PVDF (Kynar or Hylar) paint finish.

  30. Sue Hofacker says:

    Todd, happy to find this site. We are building a small cottage in central VA & are being encouraged to use the Tuff-Rib product. We will be using closed cell foam insulation in the entire structure, including the cathedral ceilings. We have been instructed to have no ventilation in the roof – none in the soffits, no ridge vent, etc. If we use a metal roof, how do we handle the ventilation requirement? Should we just stick with asphalt shingles?

    • toddmiller says:

      This is a great question. Metal roofs in fact are often used on the construction you describe, and work very well for it.

      There is no special ventilation requirement for metal roofs. In fact, though, the International Building Code calls for ventilation for all structures. That said, the sort of insulated conditioned “hot roof” construction you’re using is pretty widely recognized and accepted by building inspectors, despite being outside of code compliance.

      Your closed cell foam will act as a vapor barrier to prevent moisture from reaching the back side of the metal roof and condensing. If possible, an additional vapor barrier behind the ceilings would not be a bad idea.

      I would encourage you to install plywood decking and underlayment and roofing on top of that rather than try to spray foam direct to the back of the metal roofing. Foaming the metal roofing can cause metal roof issues (research is being done in that area as I write) but, more than that, it’s a real pain if the roof needs to be replaced some day.

      The benefit to metal roofing for your application is that the metal will be unaffected by heat that may accumulate beneath of it. That is not necessarily the case with asphalt shingles.

      I hope this helps. Please contact me anytime.

  31. Andrea Pisano says:

    We are thinking about replacing our shingled roof that was damaged from Hurricane Matthew with a 29 gauge metal roof. Have had traditional roofing contractors though tell us that since we are in 10 miles from the coast in SC it’s not a good idea. They are saying a system with exposed fasteners will fail a relatively short period of time (7-10 years). Can you please advise us? Thank you.

    • toddmiller says:

      Part of me wants to defer to the professionals who have experience in your area. With being that far off the coast, though, I would not expect the salt environment to pose a huge problem. However, it indeed may be necessary to tighten the fasteners after 7 – 10 years and perhaps replace the fasteners after 15 – 20 years.

  32. Jackie Joiner says:

    Todd, I really need your advice. I am trying to make the best decision for a new roof and you offer the best information of any website I have found. I have met with and received estimates from four different roofers. I live in North Alabama and my home currently has a one layer shingle roof. Two have suggested 26 gauge and two have suggested 29 gauge, but all four use exterior fasteners. From your advice I now know that 26 gauge would be best. My question is: What is your thoughts on cutting out two inches of shingles at the ridge, installing the metal roof and having a metal ridge vent the length of the house? Also, if I only have the choice of 29 gauge metal with exterior fasteners with screws or architectural shingles both over existing shingles, which way is the smarter way to go. I’m on a fixed income, so I’m just trying to make the best decision for the money. I greatly appreciate any thoughts you could share with me, and I thank you for helping folks like me who are only educated about roofing by the internet. God Bless!

    • toddmiller says:

      I am a firm believer in good ventilation for most buildings. If you have relatively “normal” construction to your home including an attic, then cutting in a ridge vent should work well. Please realize that they ridge vent will function as an exhaust vent so you must have intake vents to feed air to it. Intake vents are normally in the soffit overhangs at the bottom of the roof. Once you have this combination of soffit vents and ridge vent, any pre existing vents in the attic should be removed or blocked off. A great source of home ventilation information is Having good ventilation helps with energy efficiency and helps avoid mold. In northern climates, it also helps avoid ice dams on the roof.

      While generally I’d be in favor of the heaver gauge, I believe that a quality paint finish, a good warranty, and proper installation are more important than gauge. I suggest a PFDV (Kynar / Hylar) coating … and make sure you know exactly what warranties you will receive at the end of the job. You should receive a warranty on the product from the manufacturer and a warranty on the installation workmanship from the contractor.

      Thank you for contacting me. Feel free to reach out anytime.

  33. Michael C. says:

    Hi Todd!
    I live in Florida, Daytona area 3 miles inland from the Atlantic. I am looking at replacing my asphalt roofing with a Metal Galvalume, 1/2 inch Standing Seam, Hidden Fastener System. Secondly what type of underlayment would be best in this situation. My home is a one story contemporary ranch type about 8,600 square foot (Big Roof). Can you offer any suggestions. Additionally do you prefer Electric powered or solar powered Exhaust fans. I need 6 or so.
    Thank you very much!

    • toddmiller says:

      Thanks so much. Please confirm what sort of warranty you will get on the product given its proximity to salt water. The underlayment actually will be specified by the Florida Building Code and the Florida Product Approval for the product you choose. You must use, at minimum, what they say to use. Generally, given the roof is at least a 3:12 pitch, I am a proponent of synthetic underlayments. Should you decide to use ice and watershed on the entire roof, it will be critical that you have good attic ventilation, both intake and exhaust. I assume you have fairly long rafter lengths so I would encourage a clip fastened standing seam rather than a “nail hem” style of panel. As far as fans … you will get greater durability in all likelihood out of electric fans. Make sure that the fans do not mess up the balance of your ventilation and start pulling air from other exhaust vents rather than your eave vents. Finally, in Florida, I’d highly recommend a PVDF coating on the roof for durability, corrosion resistance, and color retention.

  34. Sharon F says:

    I can’t find a depreciation schedule for 26 gauge ‘Ag’ metal roofing, can you point me to an industry standard schedule?
    What will type of paint used on the metal will give the longest lifespan?

    • Todd Miller says:

      So many factors affect roof life expectancy. For tax depreciation purposes, I do not believe the IRS differentiates between roofing materials. I believe the depreciation period is 39 years for all components including roofing of owner-occupied buildings, and 27.5 years for roofing on rental properties.

      The most respected and longest lasting paint systems on the market today are PVDF coatings commonly sold under the trade names of Kynar 500 and Hylar 5000.

      Please contact me anytime. My direct email is

  35. Brian Hoober says:

    Brian (again)
    Todd, I will definitely need to redeck along the eves of the house completely as the 3/8 3 ply plywood has a fair amount of rot.
    I will at least replace the 4 x 8 plywood all along the eves. This will be about a third of the roof deck.
    If I decide to tear off and redeck the entire roof should I go with
    1/2 inch 4 ply plywood or
    5/8 inch plywood?

    • Todd Miller says:

      Hello Brian.

      Most roofing performance tests have been done on 1/2″ or thinner decking. 1/2″ also meets all building codes I am aware of. You can certainly use 5/8″ but I do not expect any increased benefit.

  36. alice joseph says:

    question for Todd…

    We have a 26 ga. galvanized steel roof c. 35 years old that was painted with calbar paint after the recommended time of exposure but continues to peel to the metal. It has been touched up frequently over the years and now after being told to let it peel over the past year needs a good paint job. No one can figure out reason for peeling. Any ideas on ways to handle this problem. I can send a photo.


    • toddmiller says:

      Alice, I assume you have contacted the folks at Calbar? My guess is that the original roof was unpainted … or if it was painted then there was a pre-existing issue with adhesion of the paint to the metal. Metal used in roofing goes through a pre-treatment process that sort of “chemically etches” the metal so paint will adhere to it. If this pre-treatment is missed or fails in some other way, paint will not stick to the metal. I can’t be sure why this is happening on your roof but I believe it is happening.

  37. michael dinardo says:

    2000sq. ft house. 3.12 pitch . looking at standing seam with clips. 26 gauge. should i take off old shingles? peal and stick or synthetic under the metal?we are retired and want this to be our last roof. any other info you give will be great. thank you mike and liz

    • Todd Miller says:

      Hello Michael.

      For standing seam, I do suggest removing the old shingles. Leaving them will likely force ripples into the panels. Metal shingles can go over old shingles but not standing seam. As far as underlayment, you want to do what’s required by building code but usually it would be a combination of synthetic and ice and watershield. I will also drop you an email with additional information.

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