I was asked the following question:
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.
My response:
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 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.
What is “oil canning” ? I was asked to sign a waiver if I installed a 24 ga smooth flat standing seam roof. Thanks
Comment by Andre Leamy — February 5, 2010 @ 10:26 am
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.
Comment by toddmiller — February 5, 2010 @ 10:42 am
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!!
Thanks
Teresa
Comment by Teresa Faulkenberry — September 14, 2010 @ 1:35 pm
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.
Comment by toddmiller — September 16, 2010 @ 6:36 am
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.
Comment by Benjamin — November 9, 2011 @ 11:50 pm
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.
Comment by toddmiller — November 10, 2011 @ 7:58 pm
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.
Comment by Floyd Rogers — January 10, 2012 @ 10:42 am
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.
Comment by toddmiller — January 10, 2012 @ 10:52 am
Well, I see that you agree that metal at 26 gauge is .018 with coatings. I assume the coating must be microscopic then?
Comment by Floyd Rogers — January 26, 2012 @ 4:55 pm
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.
Comment by toddmiller — January 26, 2012 @ 5:07 pm
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.
Comment by Floyd Rogers — January 26, 2012 @ 6:00 pm
http://www.pkmetal.com/PDF_formats/steel/sheet_coil.pdf
Comment by Floyd Rogers — January 26, 2012 @ 6:05 pm
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: http://www.metalcentral.com/
Comment by Floyd Rogers — January 26, 2012 @ 6:53 pm
Thanks. I cannot vouch for them but I will include your link.
Comment by toddmiller — January 26, 2012 @ 7:41 pm
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
Comment by toddmiller — January 26, 2012 @ 7:46 pm