Roofing Nails and Wind Zones: What Code Actually Requires

The nail itself is specified, precisely

IRC Section R905.2.5 describes the fastener in more detail than most people expect. Fasteners for asphalt shingles must be “galvanized steel, stainless steel, aluminum or copper roofing nails, minimum 12-gage [0.105 inch] 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.”

Four separate requirements live in that sentence: material, shank gauge, head diameter, and embedment. The standard behind it is ASTM F1667, the specification for driven fasteners — nails, spikes and staples. Note the embedment rule has a second half in practice: where the sheathing is thinner than 3/4 inch, the nail must penetrate fully through it. That is why deck thickness and nail length are the same conversation.

How many: the code sets a floor, the manufacturer sets the number

This is the part most often misquoted. IRC Section R905.2.6, “Attachment,” reads: “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.”

Read the order of that sentence carefully. The governing document is the manufacturer’s instructions. The code’s “four per strip shingle” is a floor beneath them, not the requirement itself. The same section adds a steep-slope rule: where the roof slope exceeds 21 units vertical in 12 horizontal (21:12), shingles must be installed per the manufacturer’s approved instructions.

Four is also the industry baseline. ARMA, the asphalt roofing manufacturers’ association, puts it plainly: “For most asphalt shingles, a minimum of four nails is required per full-size strip shingle.” Placement is as specified as the count — nails belong below the sealant strip but above the area that stays visible, and no nail head should sit less than an inch from either end of the shingle.

Above that floor, the number is genuinely product-specific, and the reason is usually the warranty rather than the code. Two examples, each quoted from the manufacturer that published it and not to be generalised to other brands:

• Atlas specifies four nails as standard — seven inches up from the bottom edge, one about an inch in from each side, two evenly spaced between — and requires six for steep-slope and mansard applications above 21:12.
• Malarkey conditions its Enhanced Wind Warranty on nail count by product tier: four nails for its architectural shingles and five for its designer shingles, “or as required by code.”

That five-nail case is the useful one, because it shows the question is not a simple “four or six.” It is whatever the specific shingle’s instructions say. So “how many nails per square” has no single correct answer, and any figure quoted without naming a shingle and a condition should be treated with suspicion. Ask for the installation instructions for the product actually being installed.

Wind speed drives the shingle class, not the nail count

IRC Section R905.2.4.1 requires asphalt shingles to be tested to ASTM D7158, the standard test method for wind resistance of asphalt shingles by the uplift force/uplift resistance method, and classified per Table R905.2.4.1. An exception allows testing to ASTM D3161 for shingles falling outside D7158’s scope, classified against the same table.

The two standards are not interchangeable, and the order matters: D7158 is the primary path and D3161 is an exception available only for shingles outside D7158’s scope. D7158 is the “Standard Test Method for Wind Resistance of Asphalt Shingles (Uplift Force/Uplift Resistance Method).” D3161 is the “Standard Test Method for Wind-Resistance of Asphalt Shingles (Fan-Induced Method).” Their class ladders differ: D7158 runs D, G and H, with H the highest; D3161 runs A, D and F, with F the highest.

What the table does is narrow your options as the design wind speed climbs. At the low end, every class qualifies. As the speed rises, Class D drops out of the D7158 column, and at the top of the table only Class H qualifies under D7158 and only Class F under D3161.

Check the table in your own jurisdiction’s adopted edition rather than trusting a reproduction, including this one. We are deliberately not printing the speed-to-class cells here: the table was restructured between IRC editions when the code moved to ultimate design wind speed (V_ult), and two separate renderings of the current-edition table we pulled disagreed with each other on one D3161 cell. That is precisely the kind of one-cell discrepancy that produces a correctly-installed, wrongly-specified roof, so the honest answer is to read Table R905.2.4.1 in the edition your jurisdiction actually adopted — and to note that adopted editions differ across the jurisdictions in this directory.

None of this changes how many nails go in. It changes which shingle you are permitted to install.

Your wind speed can change at a street

The design wind speed is not a state or even a city value in much of the Front Range. Several jurisdictions in this directory publish zones drawn on named streets.

• Denver publishes three: east of Federal Blvd. requires a 115 mph minimum rating, Federal to Sheridan 125 mph, and Sheridan to Kipling 140 mph. Its Table R301.2 entry lists the wind design speed as “115/125/140” with Special Wind Region “Yes.” The required rating changes twice as you drive west across one city.
• Boulder records a three-second gust velocity of 150 mph east of Broadway and 165 mph west of Broadway, with topographic effects and special wind region both “Yes.”
• Arvada splits at Highway 93: “East of Highway 93 — 136 Vult” and “West of Highway 93 — 150 Vult.”
• Larimer County treats the issue county-wide: “Much of Larimer County is a High-Wind Area (Ultimate Design Wind Speeds equals or exceeds 140 mph). Roof coverings must be rated for the site wind speed and attached per the manufacturer.”

Read the Larimer sentence closely, because it states the whole guide in one line: rated for the site wind speed, and attached per the manufacturer. Two requirements, two different sources.

For contrast, the north Texas jurisdictions in this directory sit far lower — Plano and Carrollton both record 105 mph ultimate design wind speed, with special wind region “No.” A shingle specification that is routine in Denver’s western zones is well above what north Texas requires.

Placement fails more roofs than count does

A correctly counted nail in the wrong place is still a defect, and manufacturers say so in capitals. Atlas’s installation instructions state: “NAIL PLACEMENT IS IMPORTANT FOR WIND RESISTANCE. INCORRECTLY PLACED NAILS WILL VOID WIND COVERAGE OF WARRANTY.” The specific failure it calls out is high nailing — driving above the nailing area — which causes the shingle layers to separate, and Atlas adds that delamination after installation does not justify a warranty claim.

ARMA describes the mechanics the same way: nails must not be underdriven, overdriven so the head cuts into the shingle, or driven crookedly, and the consequences it lists are sealing failures, blow-offs, raised tabs and buckling. Its remedy is worth knowing because it is specific — an underdriven nail can be tapped flush, but an overdriven or crooked one should be removed, the hole repaired with ASTM D4586 roof cement, and a new nail placed nearby.

This is why a wind-damage claim can turn on nail placement rather than nail count, and why photographs of the nailing line matter during a tear-off.

Where six nails IS the code — a small Front Range cluster

The IRC floor is four, but a handful of Colorado jurisdictions have written six into their own published roofing requirements. If you work the Front Range, these are the addresses where “four is code” is the wrong answer.

• Parker states it as a single row in its Building Division re-roofing requirements: “Asphalt shingles — 6 nails per shingle — ASTM-D7158(D, G, H) or 3161(A,D,F) minimum, 90 mph, 3 second gust exposure C.” Note that the town bundles the fastener count and the shingle wind classification into one requirement.
• Wheat Ridge lists “six nails per shingle” among its roofing requirements, alongside the ice-and-water shield extending two feet inside the exterior wall line and a two-layer maximum.
• Bow Mar specifies a minimum wind rating of “6 nail all, 90 MPH ASTM UL D3161” on its own Roof Specifications page.

Several neighbours stop short of a number but still push past the floor. Westminster states that the city “is in a special wind region and will require high wind nailing as per manufacturer requirements for high wind for all asphalt shingle installations” — a requirement to follow the enhanced pattern without naming a count. Hudson requires fasteners meeting manufacturer instructions and ASTM F1667 for 115 mph ultimate, exposure C, and Federal Heights requires materials and fastening methods rated for 115 mph wind.

Outside this cluster, six-nail mandates are rarer and mostly live in genuine high-wind jurisdictions elsewhere — Florida’s High-Velocity Hurricane Zone in Miami-Dade and Broward counties requires six approved roofing nails under the Florida Building Code’s HVHZ provisions, while the rest of Florida mirrors the IRC’s four-nail floor.

So when a contractor says “six nails is code,” the honest answer is: in Parker, Wheat Ridge and Bow Mar it genuinely is. Elsewhere in this directory, six is usually the manufacturer’s requirement for a steep slope or a warranty tier — which is still binding, just binding through a different document.

What to actually check on a bid

Three questions settle most of it, and all three have documentary answers.

• Which wind zone is the address in? Not the city — the zone. Denver, Boulder and Arvada all publish street boundaries, so an address two blocks away can carry a different minimum rating.
• What class is the proposed shingle, and under which standard? D7158 Class D, G or H, or D3161 Class A, D or F. Check it against Table R905.2.4.1 for the site wind speed rather than assuming a premium product clears it.
• What does that shingle’s installation instruction require for fasteners? The code floor is four per strip shingle; the instructions govern above that, and the enhanced wind warranty typically depends on following them exactly, including nail placement.

For the fastener itself and the standard behind it, see Roofing Nails. For the components at the edges and penetrations that the same inspection covers, see drip edge and where code requires an ice & water barrier.