How long roofing nails do I need for my roof?
Short answer. For a standard shingle roof on 7/16 or 1/2 inch decking, 1 1/4 inch roofing nails are the usual choice. Use 1 1/2 to 2 inch nails for ridge caps, thick designer shingles or anywhere you are nailing through extra layers, and check the shingle wrapper because the manufacturer's instructions control.
Nail length by job
- Field shingles on 7/16 OSB or 1/2 inch plywood: 1 1/4 inch.
- Field shingles on 5/8 or 3/4 inch decking: 1 1/4 inch usually still reaches the required 3/4 inch into the deck, but confirm with the wrapper.
- Starter strip: 1 1/4 inch.
- Hip and ridge caps: 1 3/4 to 2 inch, because the cap folds over and you are nailing through several layers.
- Heavy designer or Class 4 shingles: often 1 1/2 inch or what the manufacturer specifies.
- Roofing over one existing layer, where your building department allows it: 1 1/2 to 1 3/4 inch to get through the old shingles.
- Underlayment: plastic cap nails, usually 1 inch, not bare roofing nails.
The rule underneath all of it
The International Residential Code requires shingle nails with at least a 12 gauge shank and a 3/8 inch head, long enough to go 3/4 inch into the sheathing or completely through it when the deck is thinner than that. They must be galvanized steel, stainless steel, aluminum or copper. Shingle manufacturers can require more, and their instructions are part of what the code enforces.
Buying tips
Coil nails for a pneumatic gun come in collated rolls, and hand nails are sold by the pound. If you are patching a few shingles, a small box of 1 1/4 inch galvanized hand nails covers most repairs.
See roof anatomy explained and roofing over existing shingles for the layers involved.