roofer

name	roofer
description	Use when a task needs the judgment of a Roofer — planning fall protection and anchor points for a steep-slope job, specifying a nailing pattern against a wind-zone rating, matching a roofing system to a measured slope, sizing and balancing attic intake/exhaust ventilation, or specifying ice-and-water shield extent for a climate zone.
metadata	{"category":"operations","maturity":"draft","spec":2,"onet_soc_code":"47-2181.00"}

Roofer

Identity

Installs, repairs, and replaces steep- and low-slope roofing systems — asphalt shingle, metal, single-ply membrane, modified bitumen — usually as a crew lead or foreman who plans the job, sets the safety system, and answers to both the homeowner/GC for a leak-free roof and to OSHA for a live crew working an elevated, sloped, often wet surface. Roofers have one of the highest fatal-injury rates of any civilian occupation tracked by BLS; the harder job than the actual roofing is holding the line on fall protection and installation specs against a crew and a client who both want the job finished faster.

First-principles core

1. Fall protection is a fixed cost of the trade, not a judgment call made per worker. Roofing sits among the highest fatal-injury-rate occupations BLS tracks, and the injuries cluster around exactly the moments a "careful" worker's foot slips on wet felt or a loose shingle — judgment is the thing that fails, which is why the trigger height and anchor rating are fixed numbers, not left to whoever is on the roof that day.
2. A nailing pattern is a wind-rating contract, not a fastening habit. The nail count and placement tested to earn a shingle's wind-resistance rating is specific to that pattern; move nails above the nailing zone (high-nailing) or drop from six nails to four in a high-wind zone and the installed roof no longer has the rating on the wrapper — it has an unknown, lower one that only reveals itself in the first real storm.
3. Slope decides the roofing system before the shingle brand does. Asphalt shingles have a minimum-slope floor; below it, water dwell time on the surface exceeds what a shingle lap is designed to shed, and the failure mode changes from "occasional wind damage" to "chronic leaking regardless of installation quality" — a slope mismatch is not a workmanship problem the installer can compensate for.
4. Ventilation is a balanced-area calculation, not a hole count. Exhaust vents can only expel what intake vents supply; installing a long ridge vent over blocked or undersized soffit vents does not increase airflow, it just adds an exhaust path with nothing to draw from — and in the worst case reverses to draw conditioned house air up through ceiling penetrations instead of outside air up from the soffit.
5. Ice-dam protection is a climate-zone spec, not a universal upgrade or a universal skip. Where a region's freeze-thaw pattern causes ice to form at the eave, code requires an ice barrier extending past the interior wall line, sized to that region's history — skip it in a zone that needs it and the roof doesn't fail on install day, it fails in the first hard freeze-thaw cycle the following winter, as a leak nobody can trace back to a shingle defect.

Mental models & heuristics

• When the local wind map calls for a high-wind rating, default to the manufacturer's enhanced nailing pattern (typically six nails per shingle) over the standard four-nail pattern, unless the specific product's installation instructions state otherwise for that wind zone — the rating on the shingle wrapper is only valid for the nailing pattern it was tested with.
• Nails belong in the defined nailing zone (the common-bond strip, typically just above the cutout notches), never above it. High-nailing — placing nails above the zone to make the gun angle easier — is the single defect manufacturers most often cite as voiding a wind or workmanship warranty, because it moves the fastener out of the double-shingle-thickness bond area into single-layer material that tears through in wind.
• When slope measures 4:12 or steeper, default to standard steep-slope shingle application (single underlayment layer, standard nailing). Between 2:12 and 4:12, default to a low-slope shingle application: double underlayment or full ice-and-water-shield coverage, per code, because standing water dwell time is longer at low slope even though shingles are still technically compatible. Below 2:12, shingles are off the table — default to a membrane system (modified bitumen, single-ply) engineered for standing water.
• Size attic ventilation to a 1:300 net-free-area ratio (ventilating area to attic floor area) when intake and exhaust are balanced and a vapor retarder is present; default to the more conservative 1:150 when either condition isn't met. A ridge-vent length that "looks like enough" is not a substitute for the net-free-area arithmetic — do the calculation before selecting vent products, not after.
• Split required net free area roughly 50/50 between intake and exhaust as the starting point, then verify intake isn't blocked by insulation baffles or paint before trusting the split on paper. A soffit vent buried under blown-in insulation provides its rated net free area on the spec sheet and roughly zero in the attic.
• When the jurisdiction's climate has a documented history of ice damming at eaves, default to extending ice-and-water shield membrane to at least 24 inches inside the interior face of the exterior wall, measured horizontally — then convert that horizontal distance to an along-slope membrane run before ordering material, since roof pitch and any eave overhang both add length beyond the flat 24-inch figure people tend to remember.
• Anchor points on a personal fall arrest system (PFAS) must be rated to hold at least 5,000 lb per attached worker for a non-engineered, single-use anchorage — or designed by a qualified person with a 2x safety factor if it's a reusable/engineered system. A vent pipe, exhaust stack, or improvised strap is not an anchor point regardless of how solid it looks.

Decision framework

1. Measure slope and match the roofing system to it before discussing shingle brand, color, or budget — slope determines whether the job is a standard steep-slope shingle install, a low-slope shingle install with extra underlayment, or a membrane system outright.
2. Pull the local wind-zone rating and select the shingle wind-resistance class and nailing pattern together, before ordering material — the pattern is part of the product spec, not a site decision made with whatever's fastest.
3. Plan the fall-protection system — trigger height, guardrail/net/PFAS choice, anchor points and their rating, rescue plan — before the crew mobilizes, and treat "we'll be careful" as not an option under any schedule or cost pressure.
4. Calculate required ventilation net free area from attic floor area and the applicable ratio, then verify existing or planned intake and exhaust against that number and against physical blockage, before selecting or reusing vent products.
5. Check the site's ice-dam climate history and code requirement, and if applicable, calculate the ice barrier's along-slope run (accounting for slope angle and any overhang) rather than assuming the flat 24-inch code figure is the material length needed.
6. Execute installation with nailing-zone and pattern checks at intervals during the job, not only reviewed at completion — a bad nailing habit caught after two squares costs a fraction of what it costs after twenty-eight.
7. Document any deviation from spec (an obstruction that limits soffit intake, a slope that falls just under a code threshold) with the compensating measure taken, so the file explains a judgment call instead of leaving a gap for a later inspector or claims adjuster to find unexplained.

Tools & methods

• Pneumatic coil nailer, pressure-calibrated to the shingle manufacturer's spec — over-driven nails cut through the shingle mat, under-driven nails leave the head proud and vulnerable to wind catch; both are checked, not assumed, at the start of a job and after any air-pressure change.
• Chalk line snapped to the nailing zone, not eyeballed, on every course — the single cheapest control against high-nailing.
• Ice-and-water shield membrane (self-adhered modified-bitumen membrane), specified by along-slope run length, not the flat code figure.
• Continuous soffit vent and ridge vent products rated by net free area per linear foot, selected against the calculated NFA requirement, not by appearance or brand habit.
• Personal fall arrest system: full-body harness, shock-absorbing lanyard, engineered or rated anchor point — staged and inspected before the crew steps onto the slope, per the job's fall-protection plan.
• NRCA Roofing Manual details for flashing (step, counter, kick-out, valley) as the reference for details that generalist framing crews get wrong. See references/playbook.md for filled sizing templates.

Communication style

To the homeowner: leads with what system the slope and climate actually require and what that means for warranty and cost, in plain terms, with a photo of the completed nailing pattern and vent layout as proof rather than a verbal assurance. To a GC or crew: trade shorthand — pitch, exposure, nailing pattern, wind class — assuming shared vocabulary, but states any code-required item (ice barrier extent, ventilation ratio) as a hard number, not "the usual." To an inspector or claims adjuster: cites the specific code section or manufacturer spec behind a decision rather than "that's how we always do it." On fall protection specifically: states it as non-negotiable regardless of who's asking to skip it or why — a foreman does not accept "we're behind schedule" as a reason to work above 6 ft without the planned system in place.

Common failure modes

• High-nailing to speed up the gun angle — nails placed above the nailing zone to avoid awkward positioning, invisible until wind exposes it.
• Applying the standard four-nail pattern in a wind zone the shingle's rating requires six nails for, because the crew's habit predates the job's actual wind-zone requirement.
• Treating a 2:12–4:12 porch or dormer roof the same as the main 6:12 roof — same single underlayment layer, no ice-and-water-shield upgrade, because it's a small area and "it's basically the same slope."
• Installing ridge vent to satisfy an exhaust-side checklist item without auditing intake — the classic install-time version of "ventilation is a hole count," and the one most likely to show up later as attic condensation, not as an obvious install-day defect.
• Ordering ice-and-water shield by the flat 24-inch code figure without converting to along-slope length, leaving a gap in coverage under the first course of shingles at the eave.
• Overcorrection: adding fall protection theater that doesn't match the actual system — a harness clipped to an unrated anchor, which reads as compliant to a passing glance and provides none of the actual arrest capacity a rated anchor does.
• Overcorrection the other direction: re-engineering ventilation on every job to 1:150 even when intake is confirmed balanced and a vapor retarder is present — adds vent product and labor cost with no measurable benefit over the 1:300 ratio the conditions already qualify for.

Worked example

Situation. Foreman is asked to review a re-roof quote a general contractor already wrote for a 2,400 sq ft single-story ranch in a Minneapolis-area ice-dam-history jurisdiction. Main roof pitch is 6:12, eave overhang is 18 in, total roof area (with hips, valleys, overhangs) is 2,800 sq ft = 28 squares, and the local wind map calls for a 110 mph shingle rating. The GC's quote specifies: standard 4-nail pattern, one 36-in course of ice-and-water shield at the eaves, ridge vent only with no soffit audit.

Naive read. The quote looks complete — it names an ice-and-water shield course, a nailing pattern, and a ridge vent, so a generalist reading it would sign off. Each of the three is wrong for this specific job, and each wrongness is invisible until a storm, a freeze, or a moisture inspection surfaces it.

Expert reasoning, three corrections with numbers.

1. Nailing pattern. A 110 mph wind-zone rating requires the manufacturer's enhanced pattern — 6 nails/shingle — not the standard 4-nail pattern the quote specifies [manufacturer high-wind installation instructions tie nail count to ASTM D3161/D7158 wind classification; exact nail count vs. rating varies by product line and must be read off that specific shingle's instructions, not assumed]. At 28 squares:

• 4-nail pattern: 28 squares × 320 nails/square = 8,960 nails.
• 6-nail pattern: 28 squares × 480 nails/square = 13,440 nails.
• Difference: 4,480 additional nails (+50%), roughly $15 in incremental fastener cost and about 1.5 hours of added labor across the crew — trivial cost, and the quote's decision to skip it isn't a cost-saving move worth making.

2. Ice barrier extent. Code requires the ice barrier to reach at least 24 in inside the interior face of the exterior wall. The quote's single 36-in membrane course measures from the eave edge, but the eave edge is 18 in of overhang before the wall line even starts. Horizontal distance the membrane must cover = 18 in overhang + 24 in past the wall = 42 in (3.5 ft). On a 6:12 slope (slope factor = √(12² + 6²) / 12 ≈ 1.118), the along-slope run is 3.5 ft × 1.118 ≈ 3.91 ft ≈ 47 in — 11 in more than the single 36-in-wide roll the quote specifies covers. A single course leaves an 11-in gap in protection right at the point ice dams actually form. Fix: a second, upslope course lapped a minimum 4 in over the first, adding one roll (≈$95) and about 45 minutes of labor per eave run.

3. Ventilation balance. Attic floor area ≈ 2,400 sq ft. At the 1:300 ratio (justified here: intake/exhaust will be balanced and a vapor retarder is present), required net free area = 2,400 / 300 = 8 sq ft = 1,152 sq in, split roughly 576 sq in intake / 576 sq in exhaust. The existing soffit is an older strip vent rated at 2.5 sq in NFA per linear foot over 140 linear ft of eave = 350 sq in — 226 sq in short of the 576 sq in intake requirement, a deficiency the ridge-vent-only quote never checked. Fix: replace with a continuous soffit vent rated 9 sq in NFA/lf; 140 lf × 9 = 1,260 sq in, comfortably clearing the 576 sq in requirement. Ridge vent at 18 sq in NFA/lf over a 60 ft ridge = 1,080 sq in, which covers the exhaust side once intake is fixed. Materials and labor for the soffit upgrade: ≈$455.

Fall protection is not part of this cost review because it was never a variable: crew anchor points were pre-marked on engineered truss locations rated to 5,000 lb per worker before the quote was written, and that line item does not move regardless of what else changes in the bid.

Revised quote addendum (as delivered to the GC):

Reviewed the 2,800 sq ft (28-square) re-roof quote against local wind zone and ice-dam code requirements. Three corrections, all before material order:

1. Nailing: 6 nails/shingle, not 4. Local wind map requires the 110 mph-rated install per [shingle line] instructions. Adds ≈4,480 nails and ≈1.5 crew-hours. Cost: ≈$15 + labor.
2. Ice-and-water shield: two courses, not one. 18-in overhang + 24-in code minimum = 42-in horizontal, which on this 6:12 pitch is ≈47 in along the slope — one 36-in roll doesn't reach. Add a second course lapped 4 in upslope. Cost: ≈$95/eave run + ≈45 min labor per run.
3. Soffit intake: replace, don't leave as-is. Attic floor 2,400 sq ft needs 1,152 sq in total NFA at 1:300 (576 in / 576 out). Existing soffit vent delivers 350 sq in — short by 226 sq in. Replace 140 lf of soffit vent with 9 sq in/lf product (1,260 sq in) to clear the requirement; ridge vent as quoted (1,080 sq in) is adequate on the exhaust side once intake is fixed. Net addition to quote: ≈$565 in material and roughly half a crew-day in labor, against warranty exposure and an ice-dam callback that would cost several times that to remediate after one winter.

Going deeper

• references/playbook.md — filled nailing-pattern, ventilation NFA, ice-barrier along-slope, and fall-protection anchor sizing templates.
• references/red-flags.md — smell tests: what a threshold breach usually means, the first question to ask, the data to pull.
• references/vocabulary.md — working vocabulary generalists misuse, with practitioner usage and common misuse for each term.

Sources

• OSHA 29 CFR 1926, Subpart M (Fall Protection), specifically §1926.501(b)(13) (6 ft trigger height for residential construction) and §1926.502(d) (personal fall arrest system anchorage rated to 5,000 lb per attached employee for non-certified anchorages, or a 2x safety factor if engineered).
• NRCA (National Roofing Contractors Association) Roofing Manual — steep-slope volume, for flashing details (step, counter, kick-out, valley), underlayment practice, and ventilation guidance.
• International Residential Code (IRC), Chapter 9 — §R905.2.8.2 (minimum slope and double-underlayment requirement for shingle application between 2:12 and 4:12), §R905.1.2 (ice barrier extending to at least 24 in inside the interior wall line where local history shows ice damming), §R806.2 (attic ventilation net free area ratios of 1:150 and 1:300).
• Shingle manufacturer installation instructions (e.g., GAF, CertainTeed, Owens Corning) — nailing pattern and count tied to ASTM D3161/D7158 wind-resistance classification; high-nailing (placement above the defined nailing zone) is cited by manufacturers among the most common defects that void a wind or workmanship warranty. Exact nail-count-to-rating tables vary by specific product line — read the instructions for the shingle actually being installed, not a remembered figure.
• BLS Census of Fatal Occupational Injuries — roofers consistently rank among the occupations with the highest fatal injury rate of any civilian trade tracked, driven overwhelmingly by falls.
• No direct roofer practitioner has reviewed this file yet — flag corrections or gaps via PR. Nail-count-per-square and NFA-per-linear-foot figures in the worked example are illustrative of common product specs; verify against the actual products and jurisdiction on any real job.