Shingles & materials
Roofing nails: count, length and nailing patterns
Most shingle blow-offs are nailing failures. The count is arithmetic; the placement and the depth are what hold a roof down.
What the code and the makers require
The International Residential Code (R905.2.5 and R905.2.6) asks for galvanized steel, stainless steel, aluminum or copper roofing nails, at least 12 gauge with a ⅜-inch head, long enough to penetrate ¾ inch into the deck or go right through it, and at least four nails per strip shingle. Shingle manufacturers add their own requirements, which govern the warranty: usually four nails per shingle in normal conditions and six in designated high-wind areas, on very steep slopes (above 21/12, where the shingle also needs hand-sealing), and for the enhanced wind warranties some products offer.
How many nails
The count follows the shingles, and the shingle count depends on the product.
| Shingle | Shingles per square | 4 nails | 6 nails |
|---|---|---|---|
| Three-tab | about 80 | 320 per square | 480 per square |
| Architectural | about 64 | 256 per square | 384 per square |
Starter strip takes four or five nails per piece, ridge and hip caps two per cap, drip edge one per foot. Together these add about a tenth to the field count.
A standard roof and a high-wind roof
22 squares of architectural shingles, four nails, 10% extra:
- 22 × 64 = 1,408 shingles × 4 = 5,632, plus 10% = 6,195 nails, about 31 lb of 1¼-inch nails, one box of 7,200 coil nails
34 squares of three-tab, six nails, 1½-inch hand nails:
- 34 × 80 = 2,720 × 6 = 16,320, plus 10% = 17,952 nails, about 109 lb, three 50-lb boxes
Both counts come from the roofing nails calculator; the squares from the shingle calculator.
Length
The nail must reach ¾ inch into a solid deck or pass through a thinner one. Add the thickness of what it goes through.
| Situation | Typical nail |
|---|---|
| Thin three-tab on a new deck | 1 in (only if it still reaches ¾ in) |
| Architectural or three-tab, one layer on a bare deck | 1¼ in |
| Thick designer shingles, or over one old layer | 1½ in |
| Ridge cap over a ridge vent, thick decking | 1¾ to 2½ in |
Short nails are the commonest nailing mistake on reroofs over an old layer and on ridge caps over vents; the ridge cap calculator flags the long nails a vent needs.
Where the nails go
Every shingle has a nailing zone marked by the manufacturer, a strip just below the sealant line.
- On three-tab shingles, four nails go in a line about 5⅝ inches above the butt, one about an inch from each end and one above each cut-out, so each nail also catches the top of the shingle below.
- On architectural shingles, the zone is where the two laminated layers overlap; nails there go through both layers and the shingle below. Nailing above the zone (a “high nail”) misses the double layer and the shingle below, and is the classic cause of blow-offs.
Six-nail patterns add a nail beside each end nail or between the others, as the wrapper shows.
Driving them
Nails go in straight, flush and snug: the head tight to the surface without cutting into it.
- Overdriven nails, common with a gun set too high, cut through the mat; the shingle can tear around the head in wind, and the warranty is void.
- Underdriven nails stand proud and wear through the shingle above.
- Angled nails leave half the head unsupported.
Set the gun’s depth on a scrap, check the first few nails on each new pitch and in changing temperatures (shingles soften in the heat), and adjust.
Staples, cap nails and other fasteners
Staples are not allowed for asphalt shingles by the code or by any major manufacturer. Cap nails and plastic-cap staples are for underlayment, not shingles: felt vs synthetic underlayment covers those. Drip edge takes roofing nails of the same metal at 12-inch centres, which the drip edge calculator counts. Step flashing is nailed to the deck only, as the flashing guide explains.
Buying them
Coil nails for a pneumatic gun come in boxes of about 7,200 (60 coils of 120); hand nails by the pound, in 1, 5, 30 and 50 pound boxes. Nails per pound fall as length rises: roughly 250 one-inch, 200 1¼-inch, 165 1½-inch. Buy one box more than the count if the next one is a drive away; a nail shortage stops a crew faster than a shingle shortage. And keep the starter, cap and flashing allowance: bundles per square and waste explains why the field count is never the whole order. The starter course itself is counted by the starter strip calculator.
A quick check on a finished roof
From a ladder at the eave, lift a shingle tab gently on a cool morning: the nails should sit in the zone, flush, four or six per shingle as specified. Nails visible on the surface, high nails, or a row of nail heads cutting through the mat are worth raising with the roofer before the final payment.