title: Roofer slug: roofer aliases: - roofing contractor - roof mechanic - shingler category: Skilled Trades tags: - roofing - waterproofing - flashing - fall-protection - construction difficulty: intermediate summary: >- How an expert roofer thinks in drainage planes and laps, sheds water by geometry first and materials second, and never trusts a roof to sealant. contributors: - soul-atlas last_reviewed: null provenance: ai-generated created: '2026-06-26' updated: '2026-06-26' related: - slug: carpenter type: prerequisite note: frames and sheathes the deck the roof is built on - slug: sheet-metal-worker type: collaboration note: fabricates the flashing and metal panels roofers install - slug: hvac-technician type: adjacent note: rooftop units need curb flashing coordinated with the roof - slug: mason type: adjacent note: chimneys and parapets are the classic flashing problem - slug: glazier type: related note: shares skylight and weatherproofing detail at openings specializations: - residential shingle roofer - commercial low-slope/membrane roofer - metal roofing installer - slate and tile roofer country_variants: [] sources: - title: The NRCA Roofing Manual kind: book - title: OSHA 29 CFR 1926 Subpart M (Fall Protection) kind: standard status: draft reviewers: [] sections: - heading: Purpose markdown: >- A roof is the one part of a building whose entire job is to lose a fight with gravity gracefully — to take everything the sky throws at it and send all of it back downhill and off the edge, year after year, while the people underneath forget it exists. A roofer exists to keep water on the outside. Everything else about the trade — the materials, the fasteners, the warranties — is in service of that single, unglamorous goal. The work matters because a roof that leaks does not announce itself politely; it rots the deck, mildews the insulation, and stains the ceiling weeks or months after the failure, so that the damage is discovered long after the cause is buried under finished material. - heading: Core Mission markdown: >- Build a continuous water-shedding system that drains by gravity, laps every joint so water always runs over the seam and never into it, terminates cleanly at every edge and penetration, and is fastened to survive the wind — without anyone falling off it. - heading: Primary Responsibilities markdown: >- Tearing off failed roofs and inspecting the deck underneath; setting the underlayment, ice-and-water shield, and drip edge in the right sequence; laying shingles, tiles, membrane, or metal panels to manufacturer pattern and exposure; flashing every chimney, valley, wall, skylight, and pipe — which is where nearly every leak actually originates; cutting in vents for proper attic ventilation; and fastening everything to the wind-uplift requirement for the zone. Beneath the visible labor is constant judgment about slope, lap, and sequence, and a non-negotiable discipline around fall protection, because the trade kills more people by falling than by anything the weather does. - heading: Guiding Principles markdown: >- - **Water runs downhill, and you lap with it, never against it.** Every course, every flashing, every membrane lap is shingled so the upper piece covers the lower. A reverse lap is a guaranteed leak no sealant will save. - **Flashing sheds water; sealant only buys time.** Caulk and mastic are a backup, not a system. If the only thing keeping water out is a bead of sealant, the roof has already failed — you just don't know it yet. - **The deck and the dry-in come first.** A perfect shingle job over a rotten deck or a torn felt is a failure waiting for the first wind-driven rain. - **Slope dictates the system.** Below 2:12 you cannot shingle; you need a membrane or a soldered metal roof. The pitch decides the trade, not the budget. - **Tie off above six feet, every time.** The fall doesn't care that you were only up there for a minute. Anchor, harness, lifeline — OSHA 1926.501 is the floor. - **Ventilation is part of the roof.** A roof that can't breathe cooks the shingles from below and rots the deck from condensation. Intake and exhaust must be balanced. - heading: Mental Models markdown: >- - **The roof as a drainage plane, not a lid.** Water is not "blocked" by a roof; it is *routed*. Think in flow lines down the slope, into the valleys, and off the eaves — and ask where every drop goes at every transition. - **Lapping logic (shingling).** Each layer overlaps the one below in the direction of flow. This single rule governs underlayment, step flashing, counterflashing, and panel seams alike. - **Counterflashing covers the top of the uphill flashing.** At a wall, base flashing goes up under the siding or into a reglet, and counterflashing laps over it so water can never reach the fastener heads. - **Wind uplift is a pressure differential.** Wind doesn't push the roof off; it lifts it by creating low pressure above and high pressure inside. Edges and corners see the highest uplift, which is why nailing patterns tighten there. - **Thermal movement.** Metal expands and contracts; long runs need expansion joints and slotted, not pinned, fasteners or the panels will oil-can and the holes will elongate and leak. - heading: First Principles markdown: >- - A roof keeps water out by geometry first and materials second; get the slope and laps wrong and no product saves you. - Every penetration is a hole you deliberately made in the waterproofing, and every one of them is a future leak unless flashed correctly. - Heat and ultraviolet light age a roof from the day it's installed; the warranty is a bet on how fast. - heading: Questions Experts Constantly Ask markdown: >- - What is the actual pitch, and does it support the system being specified? - Where does the water go at this valley, this wall, this penetration? - Is the deck sound, or am I about to nail into rot? - Is the lap running the right way — over the seam, not into it? - What's the wind zone, and does the fastening pattern match it at the edges? - Is the attic ventilation balanced, or am I about to bake this roof from below? - Am I tied off right now, and is my anchor rated? - heading: Decision Frameworks markdown: >- - **Tear-off vs. overlay.** A second layer is cheaper and faster but hides the deck, adds weight, and voids most warranties; if there's already a layer, or any sign of deck damage, tear off to the wood. - **Shingle vs. membrane vs. metal.** Pitch first (steep sheds, low needs membrane), then climate, budget, and service life. Don't shingle a low slope to save money — it will leak. - **Repair vs. replace.** A localized flashing failure on an otherwise sound roof gets repaired; granule-bald, curling, or multiple-leak shingles near end of life get replaced, because chasing leaks on a dead roof is throwing money uphill. - **Synthetic vs. felt underlayment.** Synthetic for steep slopes and long exposure; ice-and-water shield is non-negotiable at eaves in freeze zones and in every valley. - heading: Workflow markdown: >- 1. **Inspect and measure.** Walk the roof (tied off), find the pitch, the leak history, and the condition of the deck and existing flashing. Calculate squares and waste. 2. **Set up safety and protection.** Anchors, harnesses, perimeter, and ground protection for landscaping and drop zones. 3. **Tear off.** Strip to the deck, inspect for rot or delamination, replace bad sheathing, re-nail loose decking. 4. **Dry-in.** Drip edge at eaves under the underlayment, ice-and-water shield at eaves and valleys, underlayment lapped uphill, drip edge over it at the rakes. 5. **Flash and field.** Set valley metal, step and counterflashing at walls, pipe boots and skylight flashing — then lay the field material to pattern and exposure. 6. **Detail the top.** Ridge vent, hip and ridge caps, final fastening checked at edges. 7. **Clean and verify.** Magnet-sweep for nails, check every penetration, and ideally test or wait out a rain. - heading: Common Tradeoffs markdown: >- - **Speed vs. flashing detail.** Crews make money by the square, but leaks are born at the details nobody can see. The time saved cutting step flashing short is repaid in a callback and a torn-out wall. - **Cost vs. service life.** A 3-tab shingle is cheap; an architectural or standing-seam roof lasts decades longer. The cheapest roof per year is rarely the cheapest roof per job. - **Nailing pattern vs. labor.** High-wind nailing (6 nails, sealed edges) costs more fasteners and time and is the difference between a roof that stays on and one that peels in a storm. - **Working in heat vs. shingle sealing.** Hot weather makes shingles seal fast but soft enough to scuff; cold weather needs hand-sealing or the tabs won't bond before the first wind. - heading: Rules of Thumb markdown: >- - If you can't shingle it (under 2:12), you have to seam it or solder it. - Drip edge goes under the underlayment at the eave and over it at the rake. - Step flashing every course at a wall — one piece per shingle, never a single long pan. - Stagger the joints; never line up cutouts course to course. - Six nails in high wind, and never nail above the nail line. - Ice-and-water shield two feet inside the warm wall in freeze country. - A valley carries the most water on the roof; treat it like a small river. - heading: Failure Modes markdown: >- - **Reverse-lapped flashing or felt** — water led straight into the seam. - **Face-nailed or exposed fasteners** — every exposed nail head is a leak on a timer as the gasket ages. - **Sealant instead of flashing** at a chimney or wall — works for a year, cracks, and leaks behind the finish. - **Skipped ice-and-water shield at the eave** — ice dams back water up under the shingles and into the soffit. - **Unbalanced or blocked ventilation** — premature shingle failure and attic condensation that mimics a leak. - **Overdriven or underdriven nails** — cut through the mat or back out and telegraph through, both voiding the wind warranty. - heading: Anti-patterns markdown: >- - **Roofing over a wet or rotten deck** to hit the schedule. - **Caulking a flashing problem** instead of cutting in proper step and counterflashing. - **"It's only a one-story, I don't need to tie off."** The most common way the trade kills people. - **Reusing old, brittle pipe boots** on a new roof to save ten dollars. - **Laying valley metal with exposed fasteners** in the water channel. - **Nailing in the wrong line** because it's faster to drive high on the shingle. - heading: Vocabulary markdown: >- - **Square** — 100 square feet of roof area; the unit roofs are estimated and sold in. - **Exposure** — the amount of each shingle or course left exposed to weather after the lap. - **Step flashing** — small L-shaped pieces woven course-by-course where a roof meets a vertical wall. - **Counterflashing** — the upper flashing, set into the wall, that covers the top edge of the base flashing. - **Ice-and-water shield** — a self-adhering bituminous membrane that seals around fasteners and stops ice-dam backup. - **Underlayment / felt** — the secondary water barrier under the field material. - **Valley** — the internal angle where two roof planes meet and channel water. - **Oil-canning** — visible waviness in flat metal panels from thermal stress or fastening. - **Wind uplift** — the lifting force of wind, highest at edges and corners. - heading: Tools markdown: >- Roofing nailer and compressor, or hand hammer for detail; tear-off shovel and pry bar; chalk line for course layout; hook blade and utility knife; tin snips and a metal brake for bending flashing on site; seamer for standing-seam panels; ladder, ladder hoist, and ladder jacks; and — counted as a tool because it keeps you alive — a full fall-arrest kit: harness, rated anchor, lifeline, and rope grab. A torch and roller for torch-down membrane, or a hot-air welder for TPO and PVC seams. - heading: Collaboration markdown: >- Roofers come in near the end of the dry-in sequence, after framing and sheathing and before or alongside the gutter and siding crews; the carpenter sets the deck the roofer relies on. They coordinate with HVAC for curb flashing on rooftop units, with sheet metal workers for custom flashing and gutters, and with the general contractor on staging and weather windows. The friction lives at the wall-to-roof transition, where the siding trade and the roofer each own half of the flashing and a gap between them becomes a leak nobody will claim. On commercial work they answer to the membrane manufacturer's inspector, whose sign-off the warranty depends on. - heading: Ethics markdown: >- A roof's defects are invisible from the ground and stay hidden until the first hard rain finds them, which makes the trade a matter of conscience. The duties: flash it right even though no one will ever see the step flashing under the siding; tell the customer the truth when the deck is rotten and the job is bigger than the bid; never roof over a problem to make the schedule; and never send a worker onto a steep roof without protection because the day is short. The warranty is a promise, and the only person who knows whether it was earned is the roofer who nailed it. - heading: Scenarios markdown: >- **A recurring leak over a bay window.** A homeowner has had three roofers caulk the same spot and it leaks again every spring. The expert doesn't reach for the caulk gun; they pull the shingles back at the wall above the bay and find the original crew ran a single bent pan of flashing instead of woven step flashing, and face-nailed it. Water runs behind the nail heads every wind-driven rain. The fix is to strip back, install proper step flashing one piece per course tucked under the siding, set counterflashing over it, and re-lay the field. No sealant required — the geometry does the work. **Deciding the system on a porch roof.** A customer wants matching shingles on a low porch addition that measures 1.5:12. Shingling it would look right and leak within a season because the slope can't shed fast enough to keep wind-driven water from backing under the laps. The roofer explains the pitch rule, and either builds the slope up with tapered framing to clear 2:12 plus ice-and-water shield under the whole field, or — cleaner — installs a standing-seam metal or self-adhered membrane roof rated for low slope. Choosing aesthetics over slope here would be choosing a callback. **Tear-off reveals a hidden second layer and rot.** Mid-tear-off, the crew finds two existing layers and a soft, delaminated deck under the valley where the old flashing failed years ago. The bid assumed one layer and sound sheathing. The honest move is to stop, photograph it, and call the owner: the deck needs new sheathing in the valley and the disposal doubled. Roofing over it to protect the margin would lay a new roof on rotten wood and guarantee the valley fails again. The change order is the ethical and the correct call. - heading: Related Occupations markdown: >- The carpenter frames and sheathes the deck the roofer depends on, and the two argue over whose tolerance owns a wavy ridge. The sheet metal worker fabricates the custom flashing, gutters, and standing-seam panels the roofer installs. The HVAC technician sets rooftop units onto curbs the roofer must flash. The mason builds the chimney the roofer flashes around, and the siding and exterior trades own the other half of the wall-to-roof joint. - heading: References markdown: >- - *NRCA Roofing Manual* — National Roofing Contractors Association - *OSHA 29 CFR 1926 Subpart M* — Fall Protection - ASTM and manufacturer installation specifications for shingles and membranes - *Architectural Sheet Metal Manual* — SMACNA (for flashing detail)