I'm getting ready to shingle a roof for a shed/outdoor office and I'm confused on if/when I should use plastic round cap roofing nails:

roofing nail

I haven't seen these used in any instructions (including the instructions that came with my shingles) or videos. Are these nails a gimmick? Or are there clear advantages to using them?

2 Answers 2


Those nails are used only for holding down the roofing underlayment. They excel at doing so whether it be old school tar paper, or the newer more durable, hi tech roof underlayments.

  • The prior version of these was amusing - instead of the plastic piece, you had a tin can lid.
    – Ecnerwal
    May 25, 2015 at 21:45
  • Is there a specific reason for using those on the underlayment (steep pitch roof, underlayment beneath tiles, added hold down for wind resistance, etc.) in roofing? I have been involved in several roof jobs and have never seen them used. The underlayment just gets rolled out and you start tiering shingles and nailing with the standard nails or staples. May 25, 2015 at 23:28
  • 2
    @FiascoLabs They reduce the amount of tearing if the underlayment is exposed to wind before it's fully shingled - with just nails, the heads much more easily tear right through. These spread the load over a much larger area. Not that much of an issue if using ice and water shield (ohh, sticky!) rather than tarpaper/felt ;^)
    – Ecnerwal
    May 26, 2015 at 1:46
  • They're actually not only used for roofing - they're useful for insulation board too. I actually own a pneumatic cap nailer that I picked up when I was doing vinyl siding.
    – Comintern
    May 26, 2015 at 2:43
  • @Ecnerwal - Ok, one of the McMansions around here had all the underlayment peeled off in a windstorm. Due to the intensity of building, the roofers couldn't keep up, so they'd roll out the underlayment and leave it for 3-4 weeks before doing the shingling. And in windy areas, you'd need to hold the underlay in place even if you were quick on the shingling. May 26, 2015 at 3:06

It is critical to add strength to the hold on the underlayment in case the top layer comes off. These are critical to the IBHS Roof standard. The greatest loss in wind storms come from water intrusion after the loss of the roof covering.

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