Should a Metal Roof be Installed Over Battens? - Metal Roofing 101 with Todd Miller

[@jasonwaynemoses1685]

Best construction video I've ever seen told me what i wanted to hear confirmed it and then made sense of why in terms i could understand. Awesome Video!!!

[@jasonwaynemoses1685]

So I'm building a single pitch saddle stall with a couple of small awnings on either side. Oh on a budget of course. Could i run the synthetic underlayment over the frame then batons every 3'?

[@thedudeaaronfyi]

Ive been researching this for months and can't get a solid answer. 2x6 fiberglass, conditioned attic, in NV zone5, (-10f with snow to 115f), high wind application. I want to install a metal roof with an air gap. my only question is, is it safe to install peel and stick (zero perm) onto entire roof deck? Im concerned that interior moisture could start adding up in the fiberglass. I like peel and stick for the benefit of sealing around penetrations.

[@kc-rj5pd]

Hi Todd. We are installing a 10/12 pitch metal roof on a 24x28 rectangular cabin with 2x10 rafters and r30 insulation with 1x8 pine T&G as exposed inside ceiling, zipboard sheathing and titanium wrap on top. It will have a full length ridge vent and soffit vents in GA. Do we need battens (furring strips) to attach the metal roof or should it fasten right to the zipboard?

[@IsaiahIndustries]

Thanks. I am glad to hear you’re placing underlayment over the Zip Board Sheathing. I am unsure whether you are using a synthetic nailed-on underlayment or a self adhering product but really that does not affect my response. You should be fine with direct to deck since you are venting the roof assembly. That will help to get rid of any warm moist air that migrates to the underside of the roof deck before it can condense due to cooler temperatures of the roof deck created by the metal. I am not a huge fan of purlins as they make the roof harder to walk, can cause deformation of the roof, and also can decrease uplift resistance. If you really want a belt and suspenders approach, you could use an entangled mesh such as RoofAquaGuard Dry Tech on the deck. This ¼” thick product creates a thermal break to help prevent temperature transmission, both hot and cold, from the roof. It can also help with sound attenuation into the roof assembly as well as put a bit of a crown in the standing seam roof panels to help take up “extra metal” in the panels and alleviate oil canning.

[@jonbergin4330]

Remodeling a log cabin with moisture issues in attic and no soffits.Plan to install 1.5 inches of polyiso sheet insulation on top of roof. Also, closed cell spray foam(4 inches)in rafter bays in attic space....rafters are flattened logs about 4-5 inches in diameter. Question: if we do horizontal and vertical battens, do we add 1/2 inch plywood on top of the battens before the metal roof installation?.....that would incur more weight on the rafters, but maybe necessary, requiring the adding of actual 2x4s or 2x6s to strengthen the rafters?..appreciate your advice...Northern Wisconsin.

[@IsaiahIndustries]

Thank you. Based on what you’re telling me, I do not feel that battens are necessary. The amount of insulation you’re adding will prevent the cold from the metal roof from conducting down into the structure where it will come into contact with warm moist air and cause it to condense (“dewpoint”). Additionally, the closed cell foam acts as a vapor barrier and will hold moisture inside the living space rather than allow it to reach the roof system. That said, you can add battens if you wish. If you do not put decking on top, make sure the metal panels you are installing are approved for application over battens. Battens without decking will make the roof harder to walk and could increase the chance of wind uplift.

[@jonsmith9708]

Don't forget screws hold way better in solid backing like battans rather then ply or sob.also the air gap helps kill the sound the rain and r value.fyi I put syntitic felt on top of battens to block metal sweat

[@swampfoot8065]

I enjoy you videos and have some questions. I am restoring an old 2 room farmhouse in texas. I have converted the gable roof to an open cathedral, adding chords near the ridge and beams at the top of the walls to keep them from bowing out. I plan to install 2 x 4 battens perpendicular to the 2 x 4 rafters (24 ' centers) then install metal roofing to the battens with no underlayment. Then will use closed cell foam in the ceiling, walls and floor. Do you think this plan is adequate for the roof (I dont think underlayment is necessary in this case since venting not required).

[@IsaiahIndustries]

This should work because the closed cell foam acts as a vapor barrier. That said, the industry is not yet fully sold on this idea of spraying foam direct to the back of the metal roof panels. Most of us would prefer to see a layer of solid decking installed. Spraying direct to the panels, for one thing, will make repair or replacement of the roof metal very difficult.

[@OLong-fv8vq]

I have an old 1950s house, 5v metal over cedar shingles. There is no sheathing under those layers, just "real" 1 x 4 cedar board 5" OC. I was told I could save the OSB money by applying a heavier 26 ga metal roofing directly to battens without sheathing. Do you think that's o.k. ? There have never been any condensation problems in my 13 years here so far. I'm in central Florida.

[@IsaiahIndustries]

Thanks for your comment. Am I correct in understanding that you’re asking about removing the existing two layers of roofing and that the bottom layer (wood shingles) is not on solid decking? So, the thought is to install metal over battens at that point. Please correct me if I am not following things correctly. However, if I am following things correctly, I would not do this. I am not a fan of the underside of metal roofing being exposed to an attic on residences. Metal is the perfect surface for condensation to occur and, in this case, it would likely happen. Here’s an article I recently wrote on the topic of condensation that may be helpful to you: blog.mcelroymetal.com/metal-roofing-and-siding/condensation-ventilation-and-your-metal-roof

[@OLong-fv8vq]

@@IsaiahIndustries Thank you for taking the time to respond, I know it is work. You are correct. My roofer says this is not an unusual path in the downtown historic area of my city... I know it's not ideal he is trying to save me $$$ with OSB at $50 and 15/32 plywood at $75 in June 2021; which I understand and appreciate. Do you think it's just a matter of making sure and having good ventilation circulation or do you think it will be something 5-10 years from now someone will say " What idiot did this!!?"

[@IsaiahIndustries]

@@OLong-fv8vq Over the years, I have been contacted by many property owners with metal roofs installed over battens and no decking. They were experiencing severe condensation issues on the back side of the metal. Avoiding condensation requires three primary things: Vapor Barrier (behind the ceilings), Insulation (on top of the ceilings), and Ventilation (meaning intake and exhaust vents to code in the attic). You can sometimes get by with just two of these but never less than two. Making sure you have ventilation to code will be critical in your situation but my general advice is never to install a metal roof on a residence without solid decking and underlayment.

[@billparsons7732]

There's a special place in heaven for experts that share their hard-earned knowledge; thank you.

[@TheDavidscc32]

Thanks for your video! I have a question for you though. I need to reroof my 3/12 pitched timber Frame home (built pre 1950) with red pine log trusses and tongue and groove roof decking. My roof is a sealed system and does not have venting (and no way to vent as there are no soffit or fascia for venting and no way to add it easily or economically). My question is that my living room area is a cathedral ceiling with no attic space. Literally it is the exposed trusses, the tongue and groove decking and the the shingles on top. I want to do an exposed fastener metal roof this summer (standing seam is too expensive for me) and was wondering if I created an air gap 1x4 cross batten boards (roughly 1.5" air gap) would be enough to vent the roof so if would not have ice dams or condensation issues? I already get crazy ice dams on my shingled roof as it is, due to heat loss from the portion of the house that is not insulated. I was also thinking about putting ice and water shield over the entire decking before installing the cross battens. I am in Michigan. Thoughts?

[@IsaiahIndustries]

Thanks for your note. These are pretty big questions you’re asking. I like the idea of cross battening. That will help with ice dams and also it should help with summer heat gain. That said, I am a bit concerned that, even with the air space, the metal roof panels may end up dropping the roof deck temperature, increasing the possibility of condensation on your ceilings. I think I would take this time as an opportunity to add some insulation on top of the roof deck, following by the airspace. If you wish, feel free to email direct to me and we can discuss things further. [e-mail]

[@Patrick.Erb.Home.Inspection]

For "Long Term" use, Remove the Shingles, check and tighten the deck and install over a synthetic under-layment. Use of lathe or batons is in most cases done poorly with too few fasteners and fasteners not attached to frame. I have seen dozens of roofs installed that in essence were only fastened to the structure with a few nails - bad idea for wind load.

[@paulmaxwell8851]

Here in Canada we regularly put metal roofing over purlins (battens) when building outbuildings and agricultural buildings. We always lay down roof underlayment first as dripping onto the insulation due to condensation can be a problem. My home is built this way too, but that's very unusual.

[@redsresearch]

your house roof probably done by ahmish

[@really2345]

Thank you for the tutorial. I am stripping the shingles off the plywood deck of a detached garage. Can I lay metal down without battens if I put a synthetic felt layer between the deck and the metal? The garage will be heated. I am worried about condensation occurring. Thank you.

[@IsaiahIndustries]

If you’re installing a vertical seam type of panel where the metal has a great deal of contact with the roof deck, I would suggest battens. My concern is you probably do not have a vapor barrier or attic insulation. With the metal in direct contact with the roof deck, the temperature of the roof deck is dropped and that creates potential for condensation on the underside of the roof deck. Getting the metal up on battens creates a thermal break to help keep the roof deck warmer and therefore less prone to condensation. Make sure the metal you choose is approved for installation over battens. I still suggest underlayment even if battens are installed.

[@redsresearch]

doesnt the use of battons creat condensation that can rot out the battons and condensation to drip in under the underlayment around the nails going thro the battons thro the underlayment and the roof deck then condensation dripping down onto the insulation?

[@IsaiahIndustries]

I am not sure I follow your questions. Sorry. Please feel free to call me at 1-800-543-8938, ext 201 and I’d be happy to talk things through. In the meanwhile, you may find this webinar to be helpful: kzbin.info/www/bejne/hIradWx5jNuYgbs

[@llllwrightllll]

Hi. I've been watching some of your videos, and have a serious question for you. I have installed shingles, metal roofs quite few times, but recently, I've found myself in a dilemma. I recently bought a manufactured home, single-wide 16' x 80'. I replaced the original gutters with 5" k-style aluminum house gutters. Although it has no leaks, I want to do some preventative maintenance to insure against potential future leaks. This home has a slightly-pitched gable style, "loose roof" in that it is attached with staples at edges. My dilemma; should I use a 100% silicone roof coating such as Henry's, or metal roofing? I have a friend that is a professional roofer that suggests completely covering my entire roof with peel & stick, ice &water shield, then stripping (furring) it out, and installing the roofing metal. I'm very concerned about condensation using either method. The roof has no eaves therefore no soffits for vents. I'm concerned about my existing roof developing condensation problems, wetting my insulation, mold, mildew. I sure don't want to create a problem, when I have none now. Can I get you opinion on this please?

[@IsaiahIndustries]

Thanks for your comment. I think you have some valid concerns. It honestly sounds like your home could be on the verge of condensation right now but, for now, things are functioning okay. We do not want to change that! As the warm moist air that is generated inside the home tries to drive toward the drier outside, if it reaches a cool surface, it will condense. I’d be concerned about ice and watershield as it will trap the moisture and increase the chance of it condensing. Also, a metal roof will be cooler so that is a concern. Additionally, if you were to ever do anything to make the walls of the home more airtight (new windows, doors, housewrap), that may force more moisture upward, increasing the potential for condensation. If what you have now works, I am hesitant to change anything. Give me a call sometime if you’d like to discuss. 1-800-543-8938 ext 201.

[@Brandon-no3vc]

So how does batons cause condensation?

[@IsaiahIndustries]

Battens do not cause condensation. I apologize if something I said indicated that. My point is that if the attic is vented and insulated properly, that is all you need to control condensation in virtually all cases. Battens do not provide any further help. Battens, though, do make the roof harder to walk and can contribute to wind uplift.

[@Brandon-no3vc]

@@IsaiahIndustries oh I thought you said something about condensation between the metal and the old roof deck if the metal was up on strapping

[@sarobinson56]

Have questions. Mountain Cabin, 7/12 pitch, cathedral ceiling/ no attic, old cedar shakes are torn off. Car decking underneath. Is the process 1). Peel and stick. 2). 1" foam board. 3).1/2" plywood. 4). Standing seam metal? Do I need 1x4 battens?

[@larsonhomeinspection9932]

1. 2" or 4" XPS foam board 2. peel and stick 3. battens or OSB screwed through foam to rafters 4. steel

[@sarobinson56]

Larson Home Inspection Thank you!

[@IsaiahIndustries]

Sorry for the delayed response, sarobinson56. Based upon what you’re telling me, yes, some form of thermal break is probably wise. Call me at 1-800-543-8938;201 if you’d like to discuss it. - Todd

[@GeneFlygene]

I’m building a new structure I’m putting 4” of polyISO on the roof then Zip sheathing, my question, can I go right over the Zip with my standing seam roof with no battens, Just straight lay down? Thanks.

[@IsaiahIndustries]

Hi Larry. Given what you have told me, you should not need battens. That said, I would encourage a layer of synthetic underlayment despite using the ZIP sheathing. I have heard of issues with fasteners blowing through the laminated underlayment on the ZIP system. I also once heard of a standing seam job where the roof panels were rubbing against the ZIP tape, and that was creating noise with expansion and contraction. If you would like me to take a closer look at your project, feel free to email plans to me at [e-mail]

[@3RTracing]

I have a new out building that has a 12 degree slope on a 16 by 24 foot roof. I live in Index WA. We have a little bit of snow every year, and lots of rain, and temps in the summer run mid 70's to high 80's occasionally. The OSB is on 2 foot center roof joists. In other words, the 2x4 roof joists are on 24 inch centers blocked every 2 feet, so the largest section of unsupported area of OSB is 2' x 2'. There are 1 x 4's on the 2x4 joists and blocks to increase the fastener areas, and increase load spreading. The OSB is covered with two layers of #30 tared felt. The room under this roof is one large open vaulted ceiling room. I was planning on attaching some Metal Sales Classic Rib 3-ft x 12-ft Ribbed Metal Roof Panel right on the felt. Is that advisable, or should I put some horizontal 1 x 4 on 2' centers to attach the roofing too? I really don't see the need or necessity but would really appreciate an opinion here.

[@IsaiahIndustries]

Hi, I received your email as well and sent you a response. Please let us know if you did not receive it. Have a great weekend! Todd

[@IsaiahIndustries]

@Kim Davis Thank you for your comment. We went back and looked at our response to this individual and it got very complicated as we sorted through his exact situation. Generally speaking, we’re not a fan of battens on top of solid decking as the battens can weaken the roof system and also impact things like dormers and gutters. However, in situations where there is limited ventilation and subsequent condensation concerns, putting the metal panels on battens (with spacing as prescribed by the manufacturer) can help keep the underside of the roof deck warmer, which helps prevent the possibility of condensation. We are always happy to address specific questions and they are best handled if sent to [e-mail] Thank you again.

[@lynnstone7152]

Great Video - thank you! I am building a seasonal home in Maine, where it is getting very hot in the summer these days. My face screwed metal roofing is on the way. I was going to directly screw it to the rafters over Duponts 'roof protector' underlayment, because it's cold now, and we want to get the roof on fast! I am concerned that I will regret not using the mylar looking reflective underlayment under battens, and that the area under the roof, which is to be a dwelling area in the summer, may be unbearably hot. Do I need battens in this case? No other insulation is planed.

[@IsaiahIndustries]

Please email me direct at [e-mail] and tell me more. You would not be able to install roofing direct to vertically oriented rafters. I in fact never suggest residential applications without solid decking, even if battens are installed on top of the solid decking. Do you have good attic ventilation? I will await your direct email reply. Thank you.

[@richardbullard7601]

Is there a problem using Treated Battens under a Galvalume metal roof

[@IsaiahIndustries]

Yes, the chemicals used to treat the wood will corrode the metal. Only untreated lumber should be used.

[@Brandon-no3vc]

so why would you have a problem that wasnt there to begin with aftwr you put metal on?

[@IsaiahIndustries]

The properties of metal can cause it to drop the temperature of the roof deck when the metal has a great deal of contact with the roof deck assembly. If the building was previously on the cusp of condensation issues, this could push it over the edge. Always important to analyze the ventilation and vapor barriers in the structure along with any insulation.

[@Brandon-no3vc]

@@IsaiahIndustries what you mean drop the temp of the deck? doesnt it raise the temp too?

[@IsaiahIndustries]

@@Brandon-no3vc Metal is a very strong, fast conductor of cold and hot. The concern when it comes to attic condensation is that, when temperatures drop at night, if the roof deck gets too cold too quickly and you still have warm moist air in the attic, it will condense against the underside of the roof deck. Here’s a link to a webinar that may be useful to you. kzbin.info/www/bejne/hIradWx5jNuYgbs

[@leeman20s98]

Mr Miller! I am building a house with 6" of open cell spray foam under the roofline with a sealed attic. I am also installing a raised seam metal roof which the installer uses 30# felt for underlayment. My question is, what type of underlayment should I use and I was going to use a perforated roofing foil over the underlayment with 1" battens that the metal roof. Is this an acceptable roof system? I want to meet code and prevent any moisture issues. I am in Clark county NV in zone 9A Hot Desert I believe. Any help is appreciated.

[@IsaiahIndustries]

Hi LeeMan 20s! The potential problems when it comes to moisture and condensation with roofing stem in virtually all cases from moisture that originates inside the structure (from bathing, cooking, laundry houseplants, etc.) migrating into the attic and then condensing on a cool surface, often the back side of the roof deck. The reason we see more of this in recent years is not because of the roof assembly but because we have made the walls / doors / windows of our homes much tighter. Moisture that used to migrate out through those things now ends up in the attic. Your use of a sealed attic and closed cell foam should be plenty to prevent moisture originating inside the home from reaching the back of the roof deck and condensing. I would use a standard roof underlayment over the plywood decking on your roof (such as a synthetic underlayment) and I see no need for battens or anything like that. That said, if you’re seeking increased energy efficiency, then battens can be helpful by creating a thermal break. You can make things even more effective by putting down vertical battens and then horizontal battens before the roofing … allowing the resulting vertically oriented air chambers to be actively vented with intake and exhaust vents using convective airflow. This will help carry heat radiating off the back of the roof to the outside before it reaches the home. If you use battens, make sure the roof panels you’re installing are approved by their manufacturer for installation over battens. -Todd

[@leeman20s98]

Todd, thank you so much for the fast reply. I was planning on using open cell foam on the entire house including the underside of the roofline. My quote for closed cell foam was over $9K more for just the roof line over the cost of closed cell. Is this a problem? Also, do I need a breathable or vapor permeable underlayment under the metal roof?

[@IsaiahIndustries]

Closed cell foam of course is better as a vapor barrier but, if you’re using the foam everywhere, I still think you will be okay. If you wanted to ventilate at all, I’d ventilate the attic rather than just beneath the roof system. If you can put a vapor barrier behind your ceilings and walls, that would be very helpful as well. As far as the roof underlayment, I would suggest a synthetic underlayment rather than 30# felt. The felt, in hot temperatures, will want to stick to the back side of the metal panels and that could lead to problems. The synthetic underlayment will breathe only through the seams, not through the product itself. There are breathable synthetics available but they are pretty expensive and I don’t feel you need them. That said, my company is beginning to stock a good breathable product from Europe. If you’re interested, email me direct at [e-mail]. This product is a little more expensive than standard synthetics but would work well.

[@kenmcf]

Can i lay metal roof on top if zip sheathing(treated OSB) with maybe an underlayment on top of the sheathing? Seems like the screws will make a water leakable hole?

[@IsaiahIndustries]

Thanks for your question. My advice is to put an additional layer of synthetic underlayment over the ZIP sheathing. As far as metal roofing, I am a huge proponent of concealed fastened, fully interlocking panels.

[@kenmcf]

@@IsaiahIndustries Thanks...actually I am in the idea phase. My previous roof which i just ripped off was 1/2 plywood, tar paper, and asphalt tiles. The roof has a 1% slope so that did not last. I am thinking just metal panels over battens..I mean its only two cars...but a question I have. ALL the websites that sell metal panels...like the classic rib..all of them recommend a much greater slope it seems...so why is it I see so many carports and patios with classic rib panels? Do they all just leak..thanks in advance...

[@IsaiahIndustries]

I strongly encourage never installing a panel at lower than its manufacturer’s recommended minimum pitch. Manufacturers would like to sell as much product as possible - if their panels worked successfully at lower pitches, they’d allow it. Metal Sales’ “Classic Rib” panel requires a 3:12 pitch. Most industry “R” and “PBR” panels require 2:12. For roof slopes less than 2:12, mechanically seamed standing seam should be used, or else another panel designed specifically for that purpose. Without decking, you will sometimes have condensation dripping from the back of the panels. There are people who use panels at lower than their recommended minimum pitch and, eventually, it comes back to bite them. Also, there are some panels manufactured specifically for carports and patio covers, such as “W” panels, that can be used on very low slope roofs. Again, always adhere to manufacturer specifications.

[@kenmcf]

@@IsaiahIndustries So what do u recommend for a 1.5% say slope...i thought at that slope water would flow...not puddle. ..I am confused bv that....if the water flows...why would it leak..flows to slow? EPDM?

[@IsaiahIndustries]

The problem is with wind-driven rain. The water can’t get off the roof quickly enough and can therefore “flood out” panel overlaps and snaplocks. Mechanically seamed standing seam would work. If not, a TPO or other quality single ply membrane is a good option.

[@shanek6582]

Should I put the tar paper down before I put down battens or should I put it over the battens? Thanks

[@IsaiahIndustries]

Though it’s not ideal either way, my recommendation is underlayment on top of the shingles before the battens are installed. The problem with installing it on top of the battens is it tends to sag between them and the sagging areas can hold moisture which causes the underlayment to rot. I do suggest spacing your battens a tiny bit so that if water is ever trying to drain down the roof, it can run between the battens. There are also battens available with drainage slots milled into them.

[@ronbonick4265]

Both !! But on top is better.. The metal can sweat and if the felt is under the battens, the battens will collect moisture ... The last roof over I did was shingles felted over it , then battens then felt, then metal,, I am getting to the point I'd just use shingles Fewer headaches ..Most places/code and warranties require the metal screws be placed into 1 1/2 in battens. 3/4 battens will crack and slpit over time allowing the screws to come loose.. the every 8-10 years get ready to change the screws ( the seals go bad) the screws come loose etc .. Just stick to plain ol shingles , its better in the long run...

[@R2Mike]

@@IsaiahIndustries yea...with that logic is saying moisture will be then trapped under the batons to really speed up the rot. Best case is to strip everything, felt then metal. By the time u put purlins, felt then metal your out about the same cost

[@ozwylde1]

You can just tell he knows WTh hes talking about. Thanks.

[@TURTLEORIGINAL]

Ruff deck. Lol.