Metal Roofing Gauge and Thickness Explained
December 31, 2015 | Filed under: Articles, Metal Roofing Gauge
A common question I receive from homeowners concerns what metal roofing gauge they should purchase. While those who ask this are hoping for a simple answer such as “only purchase 26 gauge,” the answer is never nearly that simple. Below I will share my thoughts on what sort of metal thickness (or gauge) is best for residential metal roofing.
First of all, I despise what I call the “gauge game.” Referring to metal thickness by gauge is an old process that I believe is antiquated and should be eliminated. It is done primarily only with steel today. Other common roofing metals such as aluminum and copper have gone on to refer to metal thickness in decimal form – representing exactly how thick the metal is in inches. This would be my preferred method for steel as well.
The Problem with Metal Roofing Gauge as Measurement
The problem with metal roofing gauge is that there is a wide range of tolerances. For example, one company might sell a product as being “24 gauge” but, in reality, the thickness of the metal could vary from 0.018″ to 0.0335″ based upon exactly how that company looks at things and how big of a tolerance they allow for. There are even different ranges referenced for steel versus galvanized steel. Overall, this creates a huge range! Now, in reality, the range will usually be narrower than what I have given above, but the fact is, this is open to interpretation and manipulation and I don’t like it one bit. I have lobbied the steel industry to change this but to no avail. I think some folks enjoy playing the “gauge game” but to me, it just hurts consumers and also hurts manufacturers who are trying to keep things honest.
My Advice
- My first piece of advice when considering metal thickness is, if you’re looking at steel, insist on knowing the decimal thickness of the steel! Trust me, the manufacturer knows what it is – it’s just a matter of whether they want to tell you. If they do not want to tell you, look for a different supplier.
- Next, even once you know the decimal thickness of steel or aluminum roofing, you need to know if that is with or without paint. You can also inquire as to what tolerance they have on their stated metal thickness. There will be some nominal tolerance both plus or minus and that’s just a reality of the metals industry. Paint, though, will make a difference to the thickness and, if you truly want to compare metal thickness “apples to apples” of various metal roofing products, you need to specify whether it is with or without the paint or another coating.
- Please know that I will take a well designed and properly installed metal roof produced from thinner metal over a thicker metal product that is poorly designed or improperly installed any day of the week. In other words, the metal thickness should not be the first consideration when choosing a metal roof.
You need to do and know:
- Make sure that the roof panel being considered is appropriate for and approved by the manufacturer for your roof’s configuration. As an example, many metal roofs have minimum pitch requirements. Never allow a product to be installed at a lower pitch than its manufacturer specifies. Other considerations are things like valleys, dead valleys, flared gables, mismatched roof pitches, and non-90-degree hips that could exist on your roof and become real issues for some metal roof products. Many times, salespeople have not been properly trained to recognize these things so they only become issues when the installation crew shows up.
- Know what sort of finish or coating is on your roof and what its expected performance is.
- Know what warranties you will get with your roof and who they will come from.
- Know if your roof is Certified Premium Quality by the Metal Construction Association. Make sure that your roof is not being produced from “secondary” metal that was rejected by other producers.
- Know how your roof panel addresses things like wind resistance, roof valleys, and fasteners. Know whether the fasteners are exposed or concealed.
- Know your installer and their experience level with projects like yours.
So, while metal thickness is not the key consideration when buying a metal roof and some folks will try to fool you on metal thickness, I understand the concern. Please understand that recommended metal thicknesses will vary based on the design and engineering of the metal product being considered.That said, here are a few general recommendations. These recommendations are with paint.
Metal Roofing Thickness Recommendations that Include Paint
Exposed fastener corrugated steel roofing: .014″ – .018″
Exposed fastener corrugated aluminum roofing: minimum .024″
Steel standing seam: minimum .024″
Aluminum standing seam: minimum .032″
Steel shingles: minimum .0145″
Aluminum shingles: minimum .0185″
Steel tile: minimum .024″
Aluminum tile: minimum .032″
Please feel free to contact me whenever you have questions. todd@asktoddmiller.com
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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I’m curious about what’s under the steal roof. One company talks about 1×4 ‘s on top of existing shingles and another uses a radiant guard underlayment. Which is better? Thanks
Thanks Brian. I appreciate your question. Here’s a link to one of the times I have written about this subject of battens: https://www.asktoddmiller.com/misc/battens-or-no-battens/
Your question though seems to be more specific — which is better between battens or a radiant barrier. I will assume the roof product you’re installing is approved for use over battens. A radiant barrier is most effective when it faces an airspace. So, to get the best of both worlds, you could do battens and the radiant barrier both. If you come down to one or the other, I’d choose battens as the air space can also help avoid winter time ice dams. That dead air space as a thermal break though is very effective at controlling summer heat gain.
You could also, as an option, do vertical battens followed by horizontal battens and the metal roof. The resulting vertically oriented air chambers can then be vented by bringing fresh air in at the bottom and exhausting through a ridge vent at the peak. That can be very effective as well.
I have 29 gauge 15foot long x 3foot wide metal roofing sheets. It has airgaps . Can I install these directly over the roofing felt? I live in baton rouge Louisiana. The heat isn’t that bad here and it doesn’t snow.
I would suggest a synthetic underlayment rather than felt as it will be less likely to stick to the back of the roofing panels. Yes, what you’re doing usually works. I would suggest a light colored metal roof or one with reflective pigment for additional energy efficiency. If your attic has limited or no ventilation, though, we should talk some more as there could be condensation concerns to discuss.
I have a double wide moble home, thank you very much for helping me out
I was think of ripping sheets of plywood to make my own 1x4s to save money . 1 sheet of plywood is 8$ & I can make 12 1x4s rather than 25$ buying 12. Haha. I’m just exploring my options to help save money. I have tyvek home wrap as well… Is that better than felt?
Tyvek house wrap must not be used as roofing underlayment. There are synthetic underlayments available that are similar but designed as vapor barriers whereas Tyvek is designed to be breathable.
The metal is galvanized silver which I sure reflects sunlight
Thank you for your help
Just to be sure, it is ok to put metal directly above the felt or is it best to run 1x4s then screw metal to them
Normally it is fine to not have the 1 x 4’s. The thermal break created by the 1 x 4’s does help with energy efficiency though. However, as I said earlier, if you have limited attic ventilation, then I can easily be swayed to saying the 1 x 4’s are a good idea. My concern without them in that case is moisture in the attic condensing on the bottom side of the roof deck because the metal roof will keep it cooler than it’s been before. So, you may not have had condensation issues before but the metal roof could create them — again, this is if you do not have good attic ventilation. It is not uncommon for double wides to not have good attic ventilation.
What metal roof brands are the best?
That’s a tough question to answer, though a very good question. There are many good companies out there producing metal roofing. Many of those companies produce products in a variety of quality grades. If I was buying a metal roof (which I don’t have to since mine is 20 years old and still looks and performs like new!), here are some things I’d look for:
PVDF Coating (sold under the brands Kynar 500 and Hylar 5000)
Meets Energy Star standards
Has UL 2218 Class IV Rating
Passing Dade County, Florida uplift tests
Concealed (hidden) fasteners
Self-cleaning valleys that carry water and debris on top of the roof system
Ability to handle flared gables (for homes that have them)
Manufactured by a proven company with a solid track record
Has the aesthetics and color I want for my home
Proper installation!
My ebook on How To Buy A Metal Roof is available at no charge if you email me a note of request at todd@asktoddmiller.com It has helpful information.
Also, if someone wants to email me with specific products or manufacturers for my input, I will be happy to tell you what I know.
What thickness for copper shingles? Imitating slate shingles 12″ x 24″. Do you recommend this type of installation? We have a 30 square roof on a 275 year old home with sagging but strong rafters and want to remove the slate weight and re-roof. The slate lays very unevenly on the purlins. We could do some leveling and sheathing,or simply replace the slate. One section is flat and solidly sheathed already. We were considering standing seam but were told you need a very flat surface to be successful. The stone gable ends are high and the midway rafters droop considerably. Thank you for your advice.
Michael, most copper shingles are from .012 – .016″ thickness. There may be some at .018″. I only know of two manufacturers of them today — my company (through our Classic Metal Roofing Systems brand) and Zappone Manufacturing in Washington. Hmmm … Reinke Shake may make a copper shingle as well. I do not think the old Revere or Vail copper shingles are in production today. I could be mistaken on Vail.
I agree with you in terms of getting some weight off the structure. I also agree that standing seam metal roofing requires a pretty smooth surface.
There are many steel and aluminum shingles available that could get you a great look and be far less costly than copper.
Centura Steel Shingle is a good option with some nice slate print coats.
Oxford Shingle is an aluminum option that could work well, too.
I’d love to know more about your project, look at photos of the home, etc. This sounds like a great project to work with you on! Feel free to email me details at tmiller@isaiahindustries.com or todd@asktoddmiller.com
Thanks and good luck. We have a large copper shingle job just about to start in Indiana — I could keep you informed of its progress if you like.
thanks for the info. BTW, Gauge is misspelled in at least one place.
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