What length of roofing nails should I use?
Short answer. Use roofing nails long enough to go at least 3/4 inch into the roof deck, or completely through it if the deck is thinner than 3/4 inch, which is the building code rule. For a typical new shingle roof over 7/16 or 1/2 inch decking that means 1-1/4 inch nails, with longer 1-1/2 to 2 inch nails at ridge caps, thick laminated shingles and anywhere you nail through extra layers.
How to work it out
- Add up what the nail passes through: the shingle (two layers at the nailing zone of an architectural shingle), any shingle beneath it at that spot, and the underlayment.
- Add the required bite: 3/4 inch into the deck, or all the way through a thinner deck.
- Round up to the next stock length.
Common situations
- New 3-tab or architectural shingles on 7/16 inch OSB: 1-1/4 inch typically goes through the deck.
- Thick premium or designer shingles: 1-1/2 inch is common because the shingle itself is thicker.
- Hip and ridge caps: 1-3/4 to 2 inch, since you nail through caps, field shingles and often a ridge vent.
- Thicker decking (5/8 or 3/4 inch plywood or planks): the nail needs a full 3/4 inch of bite, so go longer.
- Overlaying an existing layer, where allowed: 1-3/4 inch or more to get through both layers into the deck.
Signs of the wrong length
Nails that are too short show up as nail pops and shingles that lift after a few Georgia summers. From the attic, a properly nailed roof over thin decking has nail tips poking through. Overly long nails matter less on shingles, but they can poke far into the attic where someone may brush against them. The shingle maker's instructions set the minimum, so read them first. See roof anatomy explained and roofing over existing shingles.