Ask Todd Miller *Metal Roofing Expert

Does A Metal Roof Need To Be On Battens?

Written by Todd Miller on September 25, 2010 | Filed under: Misc,Roofing Answers

A homeowner by the name of Ed wrote the following to me:

Todd,

I have removed all the old shingles from the roof boards (not plywood) the roof is in great shape and have installed an ice shield over the roof. Can I install the metal roof over the Ice shield or do I need the 1 X 4 boards every 2 feet as well, It’s a low slope roof thus the ice shield for extra protection.

Ed

Here’s my response:

Ed, that is a great question. Thanks for contacting me. I have several thoughts:

1) Not all metal roofs can be installed over battens like that. Before even considering it, make sure the product you’re installing is approved by its manufacturer for that type of application.
2) Basically all metal roofs that can be installed on battens can also be installed on solid decking with underlayment. Well, there are some exceptions with some of the batten mounted tile and shake profiles but that is about it.
3) Ice and Watershield products are a vapor barrier – they do not breathe. This makes attic ventilation a special concern when those products are used. They can trap moisture inside an attic and that moisture can then find a place to condense.
4) It sounds like the metal panels you’re installing probably have a great deal of contact with the underlayment, unless they are installed on top of battens. This is the case with most vertical seam products.
5) If you do not have good ventilation in the attic, then I have some concern about installing the metal roof without battens. The low pitch of your roof indicates to me that perhaps you may not have much ventilation. And, keep in mind that good ventilation requires both intake of fresh air (usually at the bottom of the roof) and exhaust (usually at or near the ridge of the roof).
6) Installing metal panels without battens can reduce the temperature of your roof decking during cool evenings. This is because the metal panels touch the underlayment which touches the decking and cold is transmitted by conductance. This could cause the decking to reach dewpoint and especially if you have a lot of moisture in the attic (caused by inadequate ventilation), this will set off condensation in the attic. Having the metal panels up on battens though stops that conduction of cold and can help avoid this situation. Keep in mind also that some metal roofs have airgaps between the metal and the underlayment / roof deck … and those airgaps can serve the same purpose as battens in this scenario.

I hope this helps.

6 responses to “Does A Metal Roof Need To Be On Battens?”

  1. toddmiller says:

    Thanks for your question and I am sorry about the problems you have experienced. First of all, it was the contractor’s responsibility to ascertain what was beneath the old roof, either through attic inspection or asking you. Next, when he found that the situation was atypical when he started the job, he should have brought his concerns to you. Next, some metal roofs can be installed over spaced boards. Some can’t. The manufacturer of your roof should be able to tell you which yours is. Finally, I am a little curious why this would cause leaks … not entirely sure that it should. Can you email photos of the roof installation to me by chance? tmiller@classicroof.com

  2. Tony Robinson says:

    I had a metal roof replaced and the contractor is upset with me as I did not tell him that I did not have a covered roof (plywood, etc) and that the old metal roof was installed on 1X4 inch boards and now that I have leaks he states it’s because I don’t have a solid roof. I’m not a roofer and most things I see on the web indicates that a solid roof is NOT required to install or replace a metal roof. My old roof only leaked in one spot where it rusted through and created a 1/8 inch hole. We had a little extra money at the time and decided to have roof replaced and which should last us a lifetime as wife and I are both in our 70’s. Thank you for a reply.

  3. toddmiller says:

    In most cases, what you are doing will be fine. The thermal break created by battens is nice but not essential in most cases. If your home has limited or no attic ventilation, though, let’s discuss this further. There could in that case be a condensation concern to discuss. I would suggest a light colored metal roof or a metal roof with reflective pigment in the coating, to achieve greater energy savings.

  4. Matthew says:

    I live in baton rouge Louisiana. I would like to install my metal sheets directly over the roofing felt without putting down 1×4 runners on the felt. The metal has air gaps for ventilating. Will I be okay? Thank you very much

  5. toddmiller says:

    I would ieally like to see the soffit vents and a ridge vent rather than the existing gable vents.

    That said, I would be surprised if the noise is from the roof. Have you had the contractor back out to take a look at it though?

  6. M.R. Brown says:

    We had asphalt roofing damaged by April 27th tornado. Roof was covered with felt under metal. On three occasions we have had very loud “noise” that seemed to be in attic but find nothing. Could it be that the extreme daytime heat is causing expansion and then contraction in the metal during the nighttime cooling? We have searched the attic, inside house and under house but find nothing. I have soffit vents and vents at each end of attic – any other ventilation recommended?

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About Todd

Todd's expertise comes from his years of experience in metal roofing manufacturing. As president of Isaiah Industries, based in Piqua Ohio, Todd runs a several of the world’s leading manufacturers of residential metal roofing; Classic Metal Roofing Systems, Kassel & Irons, and Green American Home. His personal goal is to educate homeowners of the long-life benefits of metal roofing.

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