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  1. #1
    Silver Member
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    North of Charlotte, NC
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    New Holland TC35A

    Default Pole Barn Question - OSB or not for Roof

    I have been studying ways to build a shop for almost 2 years now. I have priced about every option possible. I have read almost every pole barn project for the past several years. Many of you have provided guidance and suggestions off-line.

    We have a lot of brick (5000) left from building our house along with shingles, so I priced a brick shop built on a concrete slab. I also priced a vinyl sided shop built on a slab. I always keep coming back to the metal pole barn option. I bought a set of plans for a 30' x 40' x 12' with a 10' x 40' open lean-to.

    I have pricing on kits (everything included) and I am pricing the option of buying metal and framing materials separate. I do have the advantage of being able to buy framing materials (trusses, posts and OSB) at very good prices. I am getting several different quotes on the metal. If I can save a few $$$ now it will help offset the cost of concrete and garage doors.

    I have 1 or 2 questions for the group. There are guys on TBN with a lot of experience and I would appreciate some advice.

    Question #1: OSB on roof vs. reflective insulation
    It will cost about $350 extra to install OSB on the roof vs. using the reflective insulation. The guys who sell the metal want to sell the insulation, but I think the OSB will add strength and keep the roof from sweating. I might have to use a strong truss, but that is OK. I am not going to put OSB on the sides, but I am leaning strongly toward putting it under the roof. Any thoughts on OSB vs. reflective insulation for the metal roof?

    The local metal supplier told me the roof would sweat with OSB if I did not install the reflective insulation, but I don't believe that is possible. The roof sweats because of the difference between the air temp below the roof and the temp of the metal itself.

    Question #2: House wrap
    Would there be any advantage in wrapping the frame with Tyvek prior to installing the metal? I am thinking that I will insulate the barn next year and the Tyvek might help. I live in NC, so the walls will get warm in the Summer sun. The additional cost would be minimal, but I am not sure about the impact of putting insulation right against the metal without some type of barrier. Houses have OSB and wrap to minimize vapor. Any thoughts or suggestions?

    Thanks for your help.

  2. #2
    Gold Member DaveOmak's Avatar
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    Sep 2009
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    Omak, Washington
    Tractor
    '53 Jubilee

    Default Re: Pole Barn Question - OSB or not for Roof

    My house was just re roofed with metal over ship lap sheeting..... permeable membrane was laid over the ship lap.... 1x4's laid on top of the membrane and metal sheeting on the 1x4's.... the air gap helps keep the house cool, quiet and remove moisture and heat build up.... the membrane keeps any "leaks" from coming through to the ship lap... That's what the roofer suggested be done... also a ridge vent was installed... If the shop is heated, ice shield would be a good idea, along the eaves, placed against the OSB....
    If you use this method, be sure to screw the 1x4 through to the "trusses" for strength....

    Dave

  3. #3
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    May 2013
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    Knox, In,
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    Ford 3400, Gizmow ZTR, Simplicity 7116H

    Default Re: Pole Barn Question - OSB or not for Roof

    Insulate the roof and forget the Tyvek - it'll only get chewed and torn..

  4. #4
    Veteran Member
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    IL
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    B2710

    Default Re: Pole Barn Question - OSB or not for Roof

    Quote Originally Posted by CentralNC View Post
    Question #2: House wrap
    Would there be any advantage in wrapping the frame with Tyvek prior to installing the metal? I am thinking that I will insulate the barn next year and the Tyvek might help. I live in NC, so the walls will get warm in the Summer sun. The additional cost would be minimal, but I am not sure about the impact of putting insulation right against the metal without some type of barrier. Houses have OSB and wrap to minimize vapor. Any thoughts or suggestions?
    Tyvek is an air infiltration barrier, it's not a vapor barrier. It's designed to transfer vapor easily. It is also advertised as a secondary water shed that can protect sheathing from water that penetrates the siding. I'm not sure what you're trying to accomplish by putting Tyvek under metal. If you're worried about rain water penetrating the metal, you'd probably be better off just putting up tar paper. It's about as good for moisture control and much less expensive, it also is permeable to vapor. If you're going to use foam insulation you don't need to do anything, it's happy being right up against the metal, and also seals against air infiltration. If you're going to use fiberglass it's tough preventing the sweating from getting moisture into the fiberglass, especially in a hot humid climate. The other problem with fiberglass insulation is the facing, which is a pretty good vapor barrier. So faced insulation might add to the problem. You're kind of in a transition climate area, it's not clear which side the vapor barrier should be on without knowing climate details and wall construction. You should visit some of the manufacturer's websites, they give great advice on what to use in different parts of the country.
    Kubota B2710, New Holland CM274 front mower, Toro Zmaster ZTR, Ford 908 bush hog, New Idea manure spreader, Swisher trail mower

  5. #5
    Platinum Member
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    Nov 2012
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    Hawthorne, FL
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    Kubota L285

    Default

    If your using 26 GA or 24 GA, I wouldn't use OSB, but if your using 29 GA, I would think you might be better off with OSB. 29 GA metal has very little structure of it's own. Obviously this depends on the type of panels as well; Rib-12, rib-6, standing seam, corrugated...

    I would half way recommend adding OSB on the inside of the walls for protection, and hanging shelving, ect. Metal is strong but it doesn't take much bumping, to make it look like crap.

    As for tyvek, years ago, when I built metal buildings, are insulation came with a tyvek type material facing the inside of the building, with bare fiberglass agaisnt the metal, held in place by being pinched between the purlions and the metal panels. The rolls where 6' wide, so they did 2 panels per roll.

    Does this building need a building permit and inspection, if so I would follow your required drawings as closely as possible, some building inspectors don't like to see variations from engineering stamped plans.

    Have you priced a PEMB? (Pre engineered metal building) They are surprisingly low cost for the square footage.

  6. #6
    Platinum Member KennyG's Avatar
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    SW Michigan
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    John Deere 2320

    Default Re: Pole Barn Question - OSB or not for Roof

    Others know a lot more about the sheathing than I do, but the extra brick brings up an interesting option. Did you think about a face brick wainscot with metal siding above it? I know someone that has that combination and it looks great. Of course, you will need to pour a little more foundation to support the brick but it would be a very high end look.

  7. #7
    Silver Member
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    North of Charlotte, NC
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    New Holland TC35A

    Default Re: Pole Barn Question - OSB or not for Roof

    Quote Originally Posted by KennyG View Post
    Others know a lot more about the sheathing than I do, but the extra brick brings up an interesting option. Did you think about a face brick wainscot with metal siding above it? I know someone that has that combination and it looks great. Of course, you will need to pour a little more foundation to support the brick but it would be a very high end look.
    I did actually think about a combination of brick and metal siding. The problem became an issue of cost. I thought that if I poured a brick ledge behind the posts then I might as well pour a slab and frame up off the slab vs. using a post frame. I think I can build a really nice pole barn with lean-to and 2 garage doors for ~$15-17k. That is non-insulated and without a roof, but includes a concrete floor. A brick side garage framed off the slab was at least $10k more.

    I agree with you about the look. The brick along the bottom really does give it a much improved look.

  8. #8
    Silver Member
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    New Holland TC35A

    Default Re: Pole Barn Question - OSB or not for Roof

    Quote Originally Posted by paulharvey View Post
    If your using 26 GA or 24 GA, I wouldn't use OSB, but if your using 29 GA, I would think you might be better off with OSB. 29 GA metal has very little structure of it's own. Obviously this depends on the type of panels as well; Rib-12, rib-6, standing seam, corrugated...

    I would half way recommend adding OSB on the inside of the walls for protection, and hanging shelving, ect. Metal is strong but it doesn't take much bumping, to make it look like crap.

    As for tyvek, years ago, when I built metal buildings, are insulation came with a tyvek type material facing the inside of the building, with bare fiberglass agaisnt the metal, held in place by being pinched between the purlions and the metal panels. The rolls where 6' wide, so they did 2 panels per roll.

    Does this building need a building permit and inspection, if so I would follow your required drawings as closely as possible, some building inspectors don't like to see variations from engineering stamped plans.

    Have you priced a PEMB? (Pre engineered metal building) They are surprisingly low cost for the square footage.
    I had planned to use 26 GA on the roof and 29 GA on the sides. I priced the reflective insulation today and it is actually more expensive than my price for OSB. I was worried about the total weight on the posts if I added OSB to the sides. It would certainly help tighten up the building though. I am not going to pull a permit for the building. You are allowed to build a bldg of this size as long as you own over a certain acreage.

    I have not priced a PEMB. I might look into them tomorrow.

  9. #9
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    Default Re: Pole Barn Question - OSB or not for Roof

    Quote Originally Posted by CentralNC View Post
    I have pricing on kits (everything included) and I am pricing the option of buying metal and framing materials separate. I do have the advantage of being able to buy framing materials (trusses, posts and OSB) at very good prices. I am getting several different quotes on the metal. If I can save a few $$$ now it will help offset the cost of concrete and garage doors.
    Provided you invest in the right complete pole building complete package, you will get not only engineered plans, but also all of the materials (without having to worry about whether they are adequate for the job, or all there), you will get complete installation instructions (to be comprehensive expect several hundred pages to include diagrams as well as photos), as well as support from people with real construction knowledge should you get stuck.

    Rarely does buying piecemeal save money in the long haul.

  10. #10
    Bronze Member
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    Browns Valley, MN, USA

    Default Re: Pole Barn Question - OSB or not for Roof

    Quote Originally Posted by CentralNC View Post
    Question #1: OSB on roof vs. reflective insulation
    It will cost about $350 extra to install OSB on the roof vs. using the reflective insulation. The guys who sell the metal want to sell the insulation, but I think the OSB will add strength and keep the roof from sweating. I might have to use a strong truss, but that is OK. I am not going to put OSB on the sides, but I am leaning strongly toward putting it under the roof. Any thoughts on OSB vs. reflective insulation for the metal roof?

    The local metal supplier told me the roof would sweat with OSB if I did not install the reflective insulation, but I don't believe that is possible. The roof sweats because of the difference between the air temp below the roof and the temp of the metal itself.
    If using osb, then 30# felt needs to be installed on top of the osb and under the roof steel. 7/16" osb prices are currently down to around $11 per sheet (roughly 35 cents per sft) and reflective insulation with adhesive pull strips attached is about 1/2 of that. (see Buy Reflective Insulation | Foil Insulation | Radiant Barrier | Vapor Barrier as an example)

    Even 29 gauge steel is plenty strong enough to carry any imposed loads, without the osb. The osb will add less than two psf of weight to the roof, so the difference in truss costs would prove negligible. And no, the roof will not sweat with the osb.

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