Four. Six on the exceptions, and the exceptions are where every argument about this actually lives, because the manufacturers do not agree on what they are. On a standard architectural shingle at 64 to the square, four nails work out to 256 a square and six to 384.
The code sets a floor and then steps aside
The International Residential Code, at section R905.2.6, says this and nothing more:
Asphalt shingles shall have the minimum number of fasteners required by the manufacturer’s approved installation instructions, but not less than four fasteners per strip shingle or two fasteners per individual shingle. Where the roof slope exceeds 21 units vertical in 12 units horizontal (21:12, 175-percent slope), shingles shall be installed in accordance with the manufacturer’s approved installation instructions.
International Residential Code, section R905.2.6
Read what that does. Four is a floor, not a specification. Above the floor, the code hands the decision to the manufacturer, whose instructions then carry the force of the code. And the one physical condition it names, a slope over 21:12, does not trigger a nail count either. It triggers another instruction to go and read the wrapper.
Wind is not in that section at all, which surprises people. The code handles wind somewhere else entirely, at R905.2.4.1, by requiring the shingle to carry an ASTM D7158 classification matched to the design wind speed. That is a property of the shingle, which is tested in a lab. It says nothing about how many nails you put through it. There is no table of fasteners by wind speed in the IRC.
So why does everyone say six?
Because the manufacturers say six, and they give different reasons for it. Put four sets of instructions side by side, and the pattern is obvious:
| Manufacturer | Standard | Increased | Trigger named |
|---|---|---|---|
| GAF, Timberline LayerLock | 4 nails | 6 nails | Local codes and enhanced wind coverage |
| CertainTeed, Landmark | 4 nails | 6 nails plus cement | Steep slopes |
| TAMKO, Heritage | 4 nails | 6 nails | High wind. Sealing above 21:12 |
| Malarkey, ESR-3150 | 4 nails | 6 nails | High wind areas and slopes over 21:12 |
GAF says wind. CertainTeed says slope. Neither is wrong and neither is complete, which is why this looks like a contested question when it is not. The two at the bottom settle it by naming both in one breath. Malarkey’s evaluation report has shingles fastened with four for slopes of 2:12 to 21:12 and states that “in high wind areas and for roof slopes exceeding 21:12” they must be hand-sealed and fastened with six.
So the chain runs like this. The code sets four and delegates upward. The manufacturer sets six, whether for wind, slope, or both. A local amendment may hard-code the high wind pattern on top of that. Four documents, one requirement, and the only one that governs your roof is the wrapper on your bundle.
The enforcement is the warranty, not the inspector
This is the part that costs money. Nothing in the code says anything about warranties, and the six-nail pattern lives in the manufacturer’s instructions, so what penalizes you for skipping it is the warranty rather than a failed inspection.
GAF’s shingle warranty states that “Special Installation for all other GAF Shingles requires use of 6 nails per shingle” together with a starter strip at the eaves and rakes, and its wind table pairs Special Installation with 130 mph against 110 mph without. Four nails where six belong does not fail an inspection. It quietly drops your coverage by 20 mph, and you find out after the storm.
TAMKO is blunter: “If High Wind Application requirements are not followed, the High Wind Application Warranty MPH, as stated on Table I in the Limited Warranty, reverts to the Standard Application Wind Warranty MPH limit.”
The clearest evidence of what the sixth nail normally buys is that Owens Corning advertises not needing it. Their SureNail products are marketed for achieving a wind warranty of 130 mph with four. Nobody sells an exemption from a rule that does not bite. The trade body says the same thing in plainer terms: the ARMA residential asphalt roofing manual (PDF) has both strip and laminated shingles fastened with four nails as the standard method and reserves six for high wind regions.
Working out how many nails per shingle you need
No manufacturer publishes nails per square, so this is arithmetic rather than a quotation. What they do publish is the pieces per square, and GAF states 64 for Timberline HDZ:
Nails in a square
shingles per square × nails per shingle
At 64 shingles a square that is 256 nails at four, and 384 at six. Read the pieces per square off your own spec sheet, because it moves with the shingle.
On a 50 by 30 building with a 6/12 roof, the roof surface is 1,677 square feet, or just under 17 square feet. That is about 4,300 nails at four per shingle and 6,440 at six. The sixth nail is not a rounding difference; it is 50 percent more fasteners and the labor that goes with them, which is exactly why it is skipped.
The nail itself is specified too
Count is only half of it. IRC R905.2.5 requires fasteners to be “galvanized steel, stainless steel, aluminum, or copper roofing nails, minimum 12-gage shank with a minimum 3/8-inch-diameter head, complying with ASTM F1667, of a length to penetrate through the roofing materials and not less than 3/4 inch into the roof sheathing.” Where the sheathing is thinner than 3/4 inch, the nail has to go all the way through it.
The manufacturers say the same thing in their own words. CertainTeed asks for 11 or 12 gauge with at least 3/8 inch heads and at least an inch of length. GAF asks for penetration of at least 3/4 inch into wood decks, or just through plywood.
Two failures come out of this and neither is about the count. A nail driven at an angle or overdriven so the head cuts the mat is not holding the shingle no matter how many of its neighbors are there. And a nail too short to reach through the sheathing on a thin deck is holding nothing at all.
Get the squares before the nails
Frequently asked
Four nails are required for a standard strip or architectural shingle, and six nails are required for the exceptions. The International Residential Code sets four as an absolute floor at section R905.2.6, then defers upward to whatever the manufacturer requires. Every major manufacturer specifies six for at least one condition, so read the wrapper on the bundle rather than relying on the code minimum.
About 256 at four nails per shingle and 384 at six, for a shingle packed 64 to the square like GAF Timberline HDZ. No manufacturer publishes a nails-per-square figure, so that is arithmetic from the pieces per square on the spec sheet, and it changes if your shingle is packed differently.
High wind, steep slope, or because your local code says so, and manufacturers differ on which they name. GAF cites local codes and enhanced wind coverage. CertainTeed cites steep slopes and adds four spots of roofing cement. TAMKO and Malarkey name both wind and slope, Malarkey specifying six for high wind areas and slopes over 21:12. If either condition applies to your roof, use six.
IRC R905.2.6 requires not less than four fasteners per strip shingle or two per individual shingle, and otherwise whatever the manufacturer instructions require. R905.2.5 specifies the nail: galvanized steel, stainless, aluminum or copper, minimum 12 gauge shank, minimum 3/8 inch head, meeting ASTM F1667, long enough to penetrate at least 3/4 inch into the sheathing or all the way through a thinner deck.
Usually, nothing is visible, but your wind warranty may be lower than you expect. GAF pairs its six-nail special installation with 130 mph coverage against 110 without. TAMKO states that if high wind application requirements are not followed, the warranty reverts to the standard wind limit. No inspector checks these requirements, and nobody finds out until a storm takes shingles off a roof that was supposed to be covered.