repairing roof of a barn

Discussion in 'Homesteading Questions' started by motdaugrnds, Mar 15, 2005.

  1. motdaugrnds

    motdaugrnds II Corinthians 5:7 Supporter

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    Hello,
    My son and I built this barn out of necessity. We knew nothing about such a construction and made many mistakes. However, here after nearly nine years, it is still standing firm ... except for the ends of the roof. This is where I need some information.

    We made the roof out of OSB board, placing tar paper over it; then coating it with tar; then placing rolled roofing on top (starting from bottom about half inches past ends of rafters and overlaping it 2 inches as going up to the top of the roof). Now we have noticed the low ends of the OSB boards (exposed to weather) on each side of the roof are rotting away and in need of repair. (The rafters are 2 x 6 and look good all around.)

    I have given this some thought and would like some feed back as to whether or not my ideas might work well.

    1. I thought of placing some flashing over the ends of the roof all the way around (on top of the present roofing and folded over the end of the rafters), placing either roofing tar or all-weather-silicone cauking under it and tacking the flashing to the rafters (both on top and over the ends).

    2. I thought of taking treated 1 x 4 boards and tacking them at the ends of the roof on top of the present rolled roofing; placing either roofing tar or all-weather-silicone cauking under it. (This, alone, would not protect the ends of the existing OSB boards from further decay.)

    I would appreciate suggestions as to how to repair this roof in as easy a way as possible as we will be doing it ourselves and neither are very well at the time. Also, I need to keep cost down.
     
  2. Buggs

    Buggs Member

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    You have a leak somewhere that is getting the OSB wet. It is probably leaking around some nail heads. Elmer had the same problem with his outhouse. The roof always leaked and you could hear Elmer cussing a blue streek whenever he used the outhouse when it was raining. You need to pile some tar on the nail heads. You cannot hope to stop leaks by putting something over the existing roof unless you cover it completely. Water will always find its way in again. Hot and cold wreck havoc on a roof and loosen the roofing around the nails, so any flashing applied over a roofing material is going to leak when the weather gets hot and things start moving around from thermal expansion.

    Buggs Bunny
     

  3. farminghandyman

    farminghandyman Well-Known Member Supporter

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    is there any way of placing solid lumber board under the osb

    OSB will not take the weather, I guess you all ready know that.

    Is it painted?? that may help some.

    on the edge of the roof use some tin called roof edging, should be placed under the tar-paper etc, but you can only do so much now, but that will keep the weather off the edge,

    or box in the soffit and the end of the roof and put on a fascia board,

    And plan on replacing the edges when the roof needs to be redone, with solid or good exterior plywood, but even ply wood will not hold up well to weather, the exterior will help, but the best is real lumber, and some roof edging, don't make a pocket for water to get under or you will really have problems, (placing the roof edging over the existing roof), and not re-roofing, if you can slide it up under,
     
  4. rambler

    rambler Well-Known Member Supporter

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    It will not work to place anything over the top of the edge of the roof - this will just funnel more water onto the OSB.

    Woulda-coulda-shoulda - OSB rots real quick, shoulda been painted or had a tin flashing on it right away on the exposed edge. I know - doesn't help you now.

    If you can get between the OSB & the coverings, put a tin flashing in there, get the coverings tarred back down to this flashing.

    Best would be to buy some tin & tin over the whole roof. Let it overhang several inches. Attach with screws at least on the edges/ ends. That will last you 40 years or so.

    If the damage is not too bad, can you scrape out the damage edge lightly & get it painted now? Just real hard to work on it with the coverings on top now.

    --->Paul
     
  5. jack_c-ville

    jack_c-ville Well-Known Member

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    For a quick, low-cost fix I would go with the flashing approach. But be sure to slide the flashing under the edge of the rolled roofing &/or the tar paper so that it will shed water properly. Trying to affix the flashing to the top surface of the roofing material with caulking will not work very well. Water will get through.

    If the roofing tar is preventing you from getting the flashing a few inches under the roll roofing then you might want to wait for a hot day to soften the tar up. Then use something along the lines of a heated, improvised, flat prybar to get under there.

    In the long run, rolled roofing is not known for being a high quality or long-lasting product. 9 years is a pretty good run for most of the stuff. When you and your son are doing a little better you might want to think about tearing the roof off and replacing it altogether.

    Exterior OSB can work fine as roof sheathing if you're prepared to do everything just right. But it is less forgiving of water than plywood is in the longrun. OSB will resist a soaking for longer than plywood will because it does not have long, continuous grain running through it that wicks moisture. Put a piece of plywood and a piece of OSB in a bucket together and the plywood will almost always swell first. Score one point for OSB. But this same anti-wicking tendency means that once it does get wet OSB also takes far longer to dry out than plywood does. Thus it is more likely to rot at the ends where the moisture has been drawn in. Problem #2 with OSB is that once it swells it stays swollen even after it drys out. Good plywood will return to within a 100th of an inch of it's original thickness when it dries out. Problem #3 is that once OSB has had a good soaking and dried out, it's water-resistant properties disappear. In it's newly expanded condition it will soak up water at a far faster rate than before, which compounds the rotting problem.

    In my opinion, OSB is the material to use if you're building a good quality house with all of the roof protection details that are available. Prolonged, repeated soakings of the sheathing in such a structure is an unlikely scenario. A simple barn or other outbuilding that you're putting less effort into is better off with plywood.

    -Jack
     
  6. motdaugrnds

    motdaugrnds II Corinthians 5:7 Supporter

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    Thank you all very much.

    I will go with the flashing placed up under the tar paper and lapped over the ends to be attached to the ends of the rafters. (Will most likely replace some of the OSB that is too damaged to hold roofing tacks.) Yes, this will be done this summer after the sun has heated the roof well. (The barn, itself, has absolutely no leaks at all. The rotted parts are only outside around the edges where the OSB has been exposed to the elements.)

    I am thinking that, on the parts where we have to replace the OSB, I might nail a "shieth" (?? the flat 2x6 or 2x4 along the ends of the rafters ??) up against the end of the newly placed OSB, thereby sheltering the ends of the OSB from the elements. Then the tar paper, tar and rolled roofing can be tacked to the shiething.
     
  7. jack_c-ville

    jack_c-ville Well-Known Member

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    That is called a 'fascia.' Smart idea. Because it is non-structural you can get away with using thinner, less expensive wood for that. 1" thick is more than enough.

    'Sheathing' refers to the structural material that lies over the rafters and covers a structure. In your case, it's the OSB.

    While you are at it, take a roller and coat the edges of the replaced OSB or plywood sheathing with a thick layer of primer. Make sure that you do this first, then let it dry completely while you have a beer or something, then put up the fascia and then add your flashing so that the flashing extends over the spot where fascia meets the rafter tails and edge of the sheathing. Otherwise water will become trapped in there, leading to rot.

    Aren't roofs a pain? Roofs and stairs are the only really complicated things involved in ordinary, entry-level carpentry. They look so simple but get incredibly complicated once you're actually doing it.

    -Jack