Our house has a typical mast for the incoming electric wires, and it has two guy wires for support. The guy wires are anchored in the roof just with half-inch bolts sticking through the shingles and sheathing, fastened to wooden blocking underneath, attached between rafters.

One of the anchors causes a continuous leak in rainy weather, about a gallon a week this time of year. The other one leaks just a tiny bit most of the time, just enough so the sheathing and nearby frame is slightly wet, but if rain is very heavy and the wind just right, it leaks enough to send water into the house.

I need to fix these, and wondered -- is this an appropriate way to anchor guy wires in a shingled roof -- to just punch a bolt through? My first thought was no, this is a dumb-nuts lazy approach almost guaranteed to leak. But I did some research and noticed others on youtube etc. do the same thing. So maybe the fix is just to apply more tar or some type of sealant around the bolts to stop the leak. Or is there some sort of anchor with proper flashing that would be better to use? In an hour of searching, I couldn't find any such part for sale, except for flat roofs.

  • I would remove the existing "tar" before putting new "tar" on. Do you have access to the bottom end of the fastener in the attic?
    – Huesmann
    Commented Dec 13, 2023 at 14:16
  • Welcome. Please take the tour so you know how to respond to answers.
    – isherwood
    Commented Dec 13, 2023 at 17:19

2 Answers 2


Many years ago when I mounted an analog TV antenna on a roof, the kit came with some of what looked like chewing gum that I thought was plumbers' putty, but may have been tar (thanks Ecnerwal!). The tar sticks went under the leg plates of the antenna stand, and the screws went through the tar sticks. For the year I had the house, I didn't see a leak.

I would try adding tar around the bolts, with some fender washers: tar around guy bolts

  • 1
    I doubt it was plumbers putty, which is not really made for all-weather outdoor use. Appeared similar to, I'd believe.
    – Ecnerwal
    Commented Dec 12, 2023 at 22:13
  • Interesting, @Ecnerwal! Doing a bit of googling for antenna roof mounts, I found it could have been tar pads. Commented Dec 12, 2023 at 22:20
  • 1
    @Ecnerwal could've been "monkey sh!t" putty, typically for sealing duct and cable entries and the like, rather than plumbers putty.
    – Huesmann
    Commented Dec 13, 2023 at 14:14
  • AKA "duct seal".
    – isherwood
    Commented Dec 13, 2023 at 16:29
  • This would require entering the attic any time the roof was replaced or repaired. I don't see the point. The washers do nothing to enhance the seal of tar, and you could accomplish the same thing from above with a shouldered eye screw (or just a regular one with washers).
    – isherwood
    Commented Dec 13, 2023 at 16:49

Bazillions of roofs have simple eye hooks through the shingles. If it was a real problem there would be under-shingle anchors or other gizmos showing up all over a quick web search. There aren't.

Some tips:

  • Consider smaller screws. Half-inch is large enough to anchor a yacht. 5/16" or 3/18" set ~3" into the framing and properly piloted is more than adequate.
  • Clean up all the old gunk around the bolts. New tar over cracked, loose sealant won't last long.
  • Seal all layers. Gently lift the shingles and seal between them.
  • Use the right product. Old-fashioned tar may work, but modern sealants which are designed for roofing are better. Don't use silicone or other general-purpose caulks.
  • 1
    When I search for under-shingle anchors, what comes up is 90% safety devices for people working on roofs. Those are great, but different. The only other thing is anchors for large racks of solar panels, which seem to be a specialty product not available at the local hardware store. They would work for my application, but might be overkill if bolt through shingles is respectable. Commented Dec 13, 2023 at 17:18
  • 1
    Not sure why the previous owner of our house used such large bolts, but now the holes are there, and they were too lazy to find rafters, so blocking was added. If I revert to smaller bolts now, not sure if anything is gained -- just holes to fill. Hardware store lists products such as "flashing and construction sealant caulk" or "clear roof sealant." These seem to be mostly clear, grey, or white, not black like tar, but I hope that is OK. Seems that I would be OK to just clean up and re-seal the existing bolts. Commented Dec 13, 2023 at 17:30

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.