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Best way to patch lag bolt holes in roof?

Renovations102 | Posted in General Questions on


I am having spray foam going onto an underside area of my gaage roof. At some point, a sat dish was installed and then moved. The first bracket and lag bolts were left on the roof and penetrate into the space being foamed.

Any ideas about how to properly patch these after removal?

Should they even be removed or just dealt with on next reroofing years from now?

I am worried about leaks and the small amount of foam disrupton if removed after the foam is done.

Thanks in advance

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  1. Expert Member
    ARMANDO COBO | | #1

    If it ain't broke, don't fix it. IMO, If its not leaking, and you don't mind seeing it (hopefully is not on the front), I would wait till you reroof.

  2. Expert Member

    If there is framing below to provide backing, you can use gasketted roof screws. They should be available in any lumberyard of BB store. If there is nothing below use the gasketted bolts they use to join panels in metal quonset huts. They are made for exactly that.
    If you are in a rush, or don't want to put much time sourcing them, buy a toilet tank bolt kit.

  3. Expert Member
    NICK KEENAN | | #3

    You don't say what kind of roof it is. On a regular shingle asphalt roof, I've had good luck patching holes like that with a piece of aluminum flashing and silicone sealant. Cut the flashing about 14"x5". The nails on the shingle should be about 6" apart so you should be able to shove the flashing between the nails up past the top of the shingle and touching the roofing felt. Try it once for fit, and trim the flashing as necessary if some is sticking out. Then fill the hole with silicone, liberally apply silicone to the bottom of the flashing, and shove it in there.

    There is an element of luck in how well this works. If the hole is right next to a roofing nail you probably won't be able to get enough flashing in.

    The pro way to fix this would be to remove and replace the two shingles that the hole goes through, roofers do that all the time. Fill the hole with silicone before putting the shingles back.

    1. Expert Member
      MALCOLM TAYLOR | | #5

      I have no idea why I assumed this was a metal roof - beyond they are on my mind because I'm in the middle of two.

  4. Expert Member
    BILL WICHERS | | #4

    +1 for replacing the damaged shingles. If there is ice and water shield underneath those particular shingles, just clean it and stick a new piece of ice and water shield over the top to patch the holes. If you just want a quick fix, get some of the black neoprene roofing sealant and fill the holes with it, leaving a larger "cap" area on the surface of the shingle. This stuff works similar to tar, but it's easier to work with.

    The spray foam won't have a problem with the holes. Closed cell foam would actually help to seal them. The worst that will happen is the foam will expand out through the holes and look weird, but you can easily trim any exposed foam off with a knife or hacksaw blade.


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