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Thread: Fixing a metal roof leak

  1. #1
    Join Date
    Apr 2008
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    Willmar, MN
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    Fixing a metal roof leak

    I recently started building a shop in a large 27 year old pole barn that is sitting on my property. One of the most urgent repairs I need to do is fix the hundreds of slow leaks in the metal roof. It appears that most of the leaks are just where the steel sheets have been nailed down. Likely the slow movement in the building structures and the thermal expansion in the metal roof has over years loosened many of the nails.

    I have never really worked with a metal roof so I am pondering some very basic things about how to do this right. At this point I have not yet even climbed to the top of the roof, as until yesterday I did not have a safety harness setup to keep my old bones from falling. Anyway, here are some of my very initial questions:

    1. I was told by a local pole barn salesman that the cheapest solution I would have is simply to replace all the nails with grommeted screws. Any opinions on this? Are the screws any more likely to withstand against the movement without slowly loosening?

    2. How long screwas are required? Same lenght as the nails or will a bit shorter (50 - 75% of the nail lengt) do?

    3. Is it likely that I will have to replace all the nails to stop the leaks, or just the nails that are visibly elevated from the surface of the roof? The entire roof is about 7500 sq ft with about zillion nails.

    4. What is the best way to remove the old nails without damaging the steel sheets?

    5. Other than trying not to fall off, what else should I know before starting the job?

    This for now anyway. I will probably have a few more questions later if I try to climb onto the roof to inspect closer. Would appreciate any experienced and knowledgeable comments.

    Pete

  2. #2
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    Jun 2008
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    1. Using the screws with the washer is the best fix.

    2. I would use screws that are longer than the nails since there is a blown out hole at that spot already. The screws come in a bunch of sizes and lengths.

    3. Replace the ones that are obviously lifted.

    4. Which kind of steel roof is it? The painted ones or the old galv? Is the roof solid or does it have a nailer board spaced every few feet? They should pull out easy with a hammer or small pry bar.

    5. If it is painted roofing, depending on the pitch, don't sit down.. it is like a huge sliding board. Don't go on the painted kind if it is wet, it is like walking on ice.

  3. #3
    Join Date
    Nov 2007
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    Southwest VA
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    the nails in the roof are most likely ring shanked with neoprene washers. they do not always pull out so easily and can make some pretty big holes when pulled out. you should go up on the roof and just see if some of the nails have just pulled out somewhat and only replace those that have done so. often the nails were driven in too tight wrecking the washer. replace with neoprene equipped screws with shanks that are thicker than the nails.

  4. #4
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    I really don't like being pessimistic, but without pictures or better description, its better to take a pessimistic view. It's hard to say what kind of nails were used 27 years ago. They could be ring-shank with washers (which I doubt, or they would not have pulled out so bad) or simply old fashioned large head roof nails. They say a modern metal roof should be good for 50 years, but if it was just galvanized sheet metal nailed with roofing nails without washers, and without the hole protected from corrosion, you might just tighten or replace whats lifted and paint the entire roof with elastomeric paint to seal the corrosion that has probably taken place. If panels are too badly corroded, they may need replacing, and if too many need replacing, consider a new roof. If you are considering insulating, think about spraying foam on the inside or as a new roof coating (That requires painting every few years as the UV will damage the foam over time.)

  5. #5
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    If you're talking about traditional corrugated roofing, the nails should be at the top of a corrugation -- which, in most cases, haven't leaked badly enough to drip in my experience. I've had the most problems with cracks that develop in the valleys -- e.g., from flexing in windstorms, pine cones and small branches dropping on them, etc. (or improper nailing done in the valleys!) Since water runs down the valleys, it's a bad place to have a crack.

    I've had good luck scrubbing them with a wire brush and caulking them with a caulk designed to adhere to the material. Make sure that the caulk is pushed down into the crack and smoothed on top so it doesn't dam up any water flowing down the valley even the slightest bit.

    The hard part is finding the cracks (and not damaging the roof more while on it). They tend to be very narrow cracks running at right angles to the corrugations.

  6. #6
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    Apr 2008
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    Willmar, MN
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    Thanks for all your replies so far. Here are some additional info:

    The roof is the kind of traditional corrugated roofing with nail rows on the top of corrugation that Wayne describes. It is galvanized steel that was originally painted white, but in some sections the paint has already come off over the years. I was told, however, that since it is galvanized this is only visual problem but won't cause any corrosion. Anyway, I am not seeing any obvious corrosion anywhere.

    So far I have been certain that the the leaks are in the nail holes. The nails are with proper washers, but quite many of them are visibly elevated from the roof level. I did not make it to the roof yet so I have not been able to make sure that there are no cracks like Michael had experienced before. I had a good intention to climb up there last weekend but I learned my ladder was not quite tall enough to make it. Will try again after ladder shopping tomorrow.

    Pete

  7. #7
    Join Date
    May 2006
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    Prairieville, Louisiana
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    Smile Although I have . . . .

    Although I have never lived in the north, I would think that a solution that would work for me here in Louisiana would be different than what would work there . . .

    Here you could probably go over the entire roof looking for raised nails, replace those with new gasketed ones. Also you use a brass wire brush in a angle grinder and some mineral spirts on all the nail locations, them liberally apply Plastic Roofing Mastic to each location. You can buy that stuff in caulk like tubes.

    But not sure if that idea would not work with the ice build up you get there. I have never seen it, but I picture huge heavy sheets of ice shearing everything off . . .

    Me, I would get half a dozen free lance roofers out there to make suggestions and bids to repair. If to high, do it yourself now that you will know what to do based on 6 different roofer's suggetions. . .
    Last edited by Steven DeMars; 07-15-2008 at 11:08 PM.
    Support the "CREEK" . . .

  8. #8
    Join Date
    Dec 2007
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    Hahira, Georgia
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    64
    Find a local metal roof sheeting supplier and get your screws there - it should be much cheaper. I paid around $30 per bag of 250 1 1/2" wooteks recently.

    You don't need the big #10 self drillers - those are for metal to metal.

    Pull a couple of nails to verify length. Get wootek screws that are 1/2" to 1" longer. They should have metal washers w/ a neoprene washer underneath that will contact the roof.

    Pick a leaking area and replace the nails in that area before moving to another area.

    Use a flat prybar and a 1X4 for bearing so you don't crush the roof ribs. Or use a second flat prybar for bearing.

    My old barn roof has 1 1/4" spiral nails with lead head caps and no leaks that I'm aware of - and it is almost 40 years old. I pulled all the wall sheeting off to make a large summer kitchen/pavillion and some of those little spiral nails required a 3' Gorilla pry bar...amazing holding power...

    Chaser

  9. #9
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    depending on how long the roof has been leaking theres a good chance that around the area where the roof was nailed down to the purlins the wood is rotted and will not hold a screw. i would pull the loose nails and seal the holes with roof cement and replace the nails with screws placed near but not necessarily in the same place as the pulled nails.

    the only way to know for sure though is to go up there. what is the pitch of the roof?

  10. #10
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    Brush Prairie, WA
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    Quote Originally Posted by Pete Kurki View Post
    I recently started building a shop in a large 27 year old pole barn that is sitting on my property. One of the most urgent repairs I need to do is fix the hundreds of slow leaks in the metal roof. It appears that most of the leaks are just where the steel sheets have been nailed down. Likely the slow movement in the building structures and the thermal expansion in the metal roof has over years loosened many of the nails.
    Hey, Pete. Boy, where to start. We also HAD (keyword, there) a metal-roofed pole barn (25x25 or so), built in 1984. So, I guess it's a year or two newer. We're not in the nastiest of climates, but we probably have a more constant rain here. I finished the last owner's attempted conversion to a real shop, and tried to repair the crummy metal roof that was on the building. After putty, mastic, replacing some screws, denting it while walking on it (be CAREFUL up there!), it was still constantly dripping on my tools. I hate to use it as an excuse, but it caused wood to warp, tools to rust, mold to grow and was generally miserable to work in. My projects would warp after bring them into the house (I guess warp may be the wrong word...how about "dry out"?) and finishes were never right.

    I could begin to list the long, long set of frustrations I had with that roof. Finally got sick of it and decided to replace the roof entirely - Was ready to pay many thousands, but found a couple of local guys in a new business to do the entire job (only a single day, not hard) for somewhere in the $1200 range, including all materials. That was R&R, new decking, paper, new shingles. That's it.

    Now, it's dry, the wood's stable, the mold is gone, most of the tools have been replaced (when I could find them under the rust piles) and the heating bill is minuscule. And I don't even have the ceiling insulation up yet. I think I had this done last summer, and it's just a joy to be in there, now.

    Seriously consider replacing the roof. For all the time and effort I spent trying to repair, block, paint, caulk, grind, scrape, nail and re-screw that old metal roof, having a new one on is so completely worth the money I can't believe I ever tried to repair it in the first place. (Looking back, at least, which is easy)

    Good luck. There are some threads here somewhere in my name that show pictures and tell the story.

  11. #11
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    When I had my pole barn built I chose to go with a composition shingle over OSB because of my experience in California with a lot of moisture created by a metal roof that had the Sun beating on it and a cooler building interior. It would actually rain inside of the building due to the temperature difference. If the building had been insulated and vented well I would not have had the problem.
    David B

  12. #12
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    Quote Originally Posted by Nathan Conner View Post
    Seriously consider replacing the roof. For all the time and effort I spent trying to repair, block, paint, caulk, grind, scrape, nail and re-screw that old metal roof, having a new one on is so completely worth the money I can't believe I ever tried to repair it in the first place. (Looking back, at least, which is easy)
    Actually replacing the roof was the first thing I thought about. Though I only got one quotation for it, and it was the original builder of this barn, thus probably not the cheapest bunch around here. The price they quoted me was $29,000! Just to replace the roof and haul away the old sheets. This is a big barn (60 x 120), but I still about fell off my chair when I heard the price. After all the same guy told me that a brand new barn of this size (shell - no insulation) would be only $75,000 erected. Of course tearing down the current barn could be another $50,000 at this rate. Anyway, I can only spend a few thousand max on it right now, so I need to try to find the best available cheap fix for now.

    Pete

  13. #13
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    The prices you quoted are way too high for a roof replacement as well as building a new barn. You need to shop around and get some prices on the roof replacement.
    David B

  14. #14
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    Okie from Muskogee, Oklahoma
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    I hope the builder wore a mask! I have two 30x60 pole barns that ran me about $4,400 each (turnkey). Thats with two slider doors, one walk in door, vents and skylights on each.
    Get some more estimates!
    Ed

  15. #15
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    Willmar, MN
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    Ed sounds like you got a deal of the lifetime. I got another quote today just for replacing the fasteners and nine steel panels that this guy decided looked like are corroding: $7,700. Looks like there is no recession here in the corn belt where biofuel has made corn and soybean farmers sudden millionaires and everyone is building new pole barns to hold their shiny new farm implements. Not that I'm jealous to hard working farmers but I hate when there is water dropping on my dried lumber...

    Pete

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