Roofing
- A ballasted roof holds a loose-laid single-ply membrane (commonly EPDM) down with stone or concrete-paver weight instead of fasteners or adhesive.
- ANSI/SPRI RP-4 is the wind design standard the International Building Code references for ballasted single-ply roofs, setting ballast rate and type by zone.
- Ballast rate is set by zone: field stone runs on the order of 10 psf, with corner rates often near double the field rate.
- RP-4 caps ballasted roof slope at roughly 2 in 12 (about 10 degrees); steeper slopes let stone migrate downslope.
- Stone ballast weighs roughly 10 to 25 psf, so a structural engineer must confirm the building carries the dead load plus snow before installation.
Codes ASTM D7655, ASTM D8231, ASCE 7
Roofing
- A blue roof detains rainwater on purpose and releases it slowly through flow-restricting drains, cutting the peak flow reaching the storm sewer.
- Ponded water weighs about 5.2 lb per square foot per inch of depth (62.4 lb/cu ft ÷ 12); a 4 in depth is roughly 21 lb/sq ft.
- A licensed structural engineer must design for the detention depth, the ASCE 7 rain load, and ponding instability before any blue roof is built.
- A secondary overflow set above the detention depth, sized for the design storm with the restrictor clogged, is mandatory and cannot be value-engineered out.
- Use a fully adhered membrane warranted in writing for ponding at design depth, and flood test it (ASTM D5957) before service or burial.
Codes ASTM D5957, ASCE 7, IBC, IPC
Roofing
- Air seal first, then insulate: insulation slows conduction but does not stop moving air, and sealing access is buried once insulation goes in.
- Uncontrolled air leakage causes roughly a quarter to forty percent of a home's energy loss, per Building Science Corporation.
- Vapor retarder goes on the warm-in-winter side; IRC requires Class I or II interior in zones 5-8 and Marine 4, none in zones 1-3.
- Give every assembly a drying path in one direction; two low-perm layers trapping the wall causes rot and needs an approved design.
- Blower-door tests at 50 pascals report ACH50; IECC commonly caps around 5 ACH50 in hot zones and 3 ACH50 in zones 3-8.
Codes ASHRAE 62.1, ASHRAE 62.2, ASHRAE 90.1, ASTM C1289, ASTM C578, ASTM E2178
Roofing
- A built-up roof (BUR) is a low-slope membrane of alternating felt plies and mopped bitumen, topped with surfacing; typically 3 to 4 plies.
- EVT (equiviscous temperature) is the bitumen temperature hitting 125 centistokes viscosity, with a working range of about plus or minus 25 degrees F.
- Interply mopping runs around 25 lbs of hot asphalt per 100 square feet; the flood coat around 60 lbs per 100 square feet.
- Codes set gravel minimums such as roughly 400 lbs of gravel or 300 lbs of slag per square; a graveled BUR commonly carries a Class A fire rating.
- OSHA hot-work benchmark: a fire extinguisher rated not less than 10B within 50 feet where more than 5 gallons of flammable liquid is in use; keep a fire watch during and after.
Roofing
- OSHA requires reporting a work-related fatality within 8 hours, and a hospitalization, amputation, or eye loss within 24 hours (1904.39).
- A competent person (1926.32(f)) must both identify hazards and have authority to stop work and correct them; a certificate or title alone does not qualify.
- OSHA's Focus Four killers are falls, struck-by, caught-in/between, and electrocution, with falls leading and topping roofing deaths.
- Post the OSHA 300A annual summary where employees see it from February 1 to April 30, even with zero recordable cases.
- An EMR (experience modification rate) runs against a 1.0 industry average; GCs often require below 1.0 to bid, so it gates prequalification.
Codes OSHA 1926, 29 CFR 1904, 29 CFR 1926
Roofing
- A cool roof needs both high solar reflectance (reflects sunlight) and high thermal emittance (re-radiates absorbed heat); bare metal reflects well but emits poorly.
- Energy codes require the three-year AGED reflectance, not the brochure initial value; white membranes often drop from near 0.80 to 0.55-0.65 aged.
- SRI (per ASTM E1980) combines reflectance and emittance into one number: standard black is 0, standard white is 100, and the scale is not capped.
- The CRRC measures and publishes initial and aged SR, TE, and SRI but sets no pass/fail thresholds; products are CRRC-rated, not CRRC-passing.
- Reflective low-slope roofs over cooled spaces cut peak cooling demand roughly 10-15 percent; reflectance does not replace the separately-required insulation R-value.
Codes ASHRAE 90.1, ASTM C1371, ASTM C1549, ASTM E1918, ASTM E1980, ASTM E408
Roofing
- In the trades the work quality is assumed; communication is what earns the review, the referral, and the repeat job.
- Responding within about five minutes converts far better than an hour later, and a lead left untouched a full day is usually gone.
- Ask for the review at the happy moment, right after the customer sees the finished work; trigger from job completion, never scheduling.
- A Google rating of 4.0 stars is roughly where customers start treating a business as trustworthy; recency and volume also drive local map ranking.
- The FTC review rule, in effect since 2024, bans fake reviews and any compensation conditioned on a review expressing a particular sentiment.
Roofing
- A customer database is the single organized record of every customer, property, job, quote, and conversation, and the most valuable asset a contractor owns.
- Odds of selling to an existing customer run about 60 to 70 percent versus roughly 5 to 20 percent for a new prospect (Marketing Metrics).
- TCPA generally requires prior express written consent before marketing texts, with statutory damages commonly 500 to 1,500 dollars per message.
- Email marketing under CAN-SPAM is opt-out but must identify the message, include a real physical address, and honor unsubscribe requests.
- Keep one record per customer that everyone updates; tie people to properties and store roof age, install date, and warranty to drive follow-up.
Roofing
- Commercial drone inspection in the US requires an FAA Part 107 remote pilot certificate, FAA aircraft registration, and airspace authorization; no hobby exception when paid.
- Part 107 caps altitude at 400 ft above ground level, with an exception to fly higher within 400 ft of a structure.
- Fly thermal roof moisture surveys about an hour after sunset on a dry roof with wind under about 15 mph; wet insulation reads warmer than dry roof.
- Standards: ASTM C1153 for infrared roof moisture, IEC TS 62446-3 (min ~600 W/m2 irradiance) for solar PV thermography, ASNT SNT-TC-1A Level I/II for thermographers.
- A drone scan is triage, not proof; confirm thermal anomalies with a moisture probe or core cut before any repair.
Codes ASTM C1153
Roofing
- Electronic leak detection (ELD) locates a membrane breach by running electrical current that water carries through the hole to the grounded conductive deck below.
- ELD requires three things: a nonconductive membrane, a grounded conductive substrate, and no insulating layer between them blocking the current.
- Dry exposed membrane gets high-voltage spark testing (up to about 12,000 V DC); wet or covered membrane gets low-voltage vector mapping (tens of volts, under roughly 50 V scanning).
- Carbon-black EPDM, butyl, and metallic-faced membranes conduct, so ELD cannot tell a breach from sound sheet; confirm membrane chemistry before scheduling.
- ASTM D7877 is the umbrella guide and D8231 the low-voltage practice, but the membrane manufacturer's requirements and project spec govern; ELD supplements, not replaces, visual and infrared inspection.
Codes ASTM D7877, ASTM D8231
Roofing
- Emergency board-up and tarping should be done in the first 24 hours to stop water, intruders, and compounding loss after a fire, storm, or impact.
- Size a roof tarp to overshoot the damage 3 to 4 ft per side, tuck the up-slope edge under existing shingles, and lap so water sheds over the top.
- Anchor every tarp edge by wrapping it on a 2x4 batten screwed into sound decking at about 12 in spacing; keep fasteners out of the field over the damage.
- A standard blue poly tarp lasts roughly four to six weeks; UV destroys it, and cheap tarps can fail in 10 to 14 days in hot, high-sun climates.
- The ISO-form mitigation duty makes reasonable securement a covered, separately billed expense, but only documented work (before photos, scope, timestamps) gets paid.
Roofing
- EPDM is a cured-rubber single-ply membrane for low-slope commercial roofs; seams are joined with splice tape and primer, never hot-air welded.
- EPDM seams are the primary leak point: clean each lap with splice cleaner, prime both surfaces, set tape, then roll across and along under firm pressure.
- EPDM comes in 45, 60, and 90 mil; 60 mil is the default commercial field, and reinforced (Type II, ASTM D4637) is standard for mechanically attached roofs.
- The three attachment methods are fully adhered, mechanically attached, and ballasted; ballast caps at about 2 in 12 slope under ANSI/SPRI RP-4.
- EPDM's four failure modes are seam failure, shrinkage, punctures (design out with a cover board), and ponding; solvent adhesives generally cannot go below about 40 degrees F.
Codes ASTM D4637, ASCE 7
Roofing
- Fascia is the vertical board capping the rafter tails and carrying the gutter; soffit is the horizontal panel closing the overhang and feeding attic intake.
- A vented soffit is the intake half of attic ventilation; continuous perforated soffit commonly provides about 9 sq in of net free area per linear foot, but size to the manufacturer rating.
- Keep the fascia level and build gutter slope into the hangers, commonly about 1/4 in of fall per 10 ft toward the downspout.
- Fasten metal and vinyl in slot centers with heads left slightly proud and cut soffit panels about 1/4 in short, so trim can float and not oil-can.
- Fascia rots from no/failed gutter, ice dams, a missing or wrong drip edge, or a soffit trapping moisture; find and fix the water source before replacing boards.
Roofing
- A structural engineer of record must approve the saturated dead load plus live and snow loads before plant selection, media depth, or anything else.
- Saturated extensive green roofs add about 15 to 30 psf; intensive roofs run 50 to 150 psf or more depending on media depth.
- Test the bare membrane watertight by flood test (ASTM D5957) or EFVM before burial; finding a buried leak is slow and expensive.
- Use engineered lightweight mineral media (80 to 90 percent expanded shale, clay, slate, or pumice), never topsoil, which compacts and overloads the roof.
- Assembly order from the deck up: membrane, root barrier, protection layer, drainage, filter fabric, engineered media, then vegetation.
Codes ASTM D5957, ASTM E2397, ASTM E2398, ASTM E2399, ASTM E2400
Roofing
- The establishment period, the first one to two growing seasons after planting, decides whether the planting survives; plants need the most water in the first 90 days.
- Target 80 to 90 percent vegetative coverage within about two years; bare media erodes, grows weeds, and thins the shield over the membrane.
- Pull tree seedlings by hand, roots and all, before they establish, because their roots grow straight toward the membrane and flashings.
- Established extensive roofs need about 2 to 3 visits a year; intensive roofs need about 8 or more plus permanent irrigation.
- Find buried leaks with electronic leak detection (EFVM), which pinpoints the breach through media and ballast; do not chase the interior stain.
Codes ASTM E2400
Roofing
- Size a gutter to two numbers: the horizontal roof area draining to it and the local design rainfall intensity; runoff flow Q = A x i x 0.0104 gpm.
- Allow about 1 square inch of downspout cross-section per 100 ft² of roof at 1 in/hr, scaled up by actual rainfall; minimum useful leader is about 7 in².
- Plan at least two downspouts per run, spaced no more than 35 to 40 ft apart, with none draining over roughly 50 ft of gutter length.
- Slope a gutter toward its downspout at least 1/16 in per foot (about 1/4 in over 10 ft); standing water means the slope is wrong.
- Space hidden hangers about 24 in on center, tightening to 16 to 18 in in snow country, because ice and snow load, not water, is what fails a gutter.
Codes IBC, IPC, IRC, SMACNA
Roofing
- Ice dams are a heat-loss problem, not a roofing-material problem. Heat warms the deck, melts snow, and meltwater refreezes at the cold eave.
- Prevent dams in three steps in order: air seal the ceiling plane first, insulate the attic floor, then ventilate the roof to hold the deck cold.
- Run ice and water shield from the lowest roof edge to at least 24 in inside the exterior wall line; on 8:12 and steeper add at least 36 in along the slope.
- Never chip or hammer ice. Rake the eave from the ground, use calcium chloride (works to about -25F) not rock salt, or hire low-pressure steam.
- Snow weight runs roughly 1 lb/sq ft per inch; wet packed snow reaches 2 lb/sq ft per inch (20 to 30 lb/sq ft per foot). Snow load is an ASCE 7 and structural engineer question.
Codes ASCE 7
Roofing
- Report a work-related fatality to OSHA within 8 hours, and an in-patient hospitalization, amputation, or eye loss within 24 hours.
- Worker error is a symptom, not the root cause; the investigation's job is to find the system fault, not the scapegoat.
- Run the 5 Whys or a fishbone diagram (man, machine, method, material, environment) past worker error until the answer is something you can engineer or manage.
- Fix corrective actions up the hierarchy of controls: eliminate, substitute, engineer, administrative, then PPE last.
- Every corrective action needs one named owner, a due date, and a verification step; keep it open until verified closed, not until promised.
Roofing
- A job hazard analysis breaks a task into steps and matches each step to its hazard and a control; OSHA Publication 3071 lays out the method.
- Apply the hierarchy of controls in order: eliminate, substitute, engineer, administrative controls, then PPE last; PPE on every line is the most common JHA failure.
- Keep a toolbox talk to 5 to 15 minutes on the day's real hazard, make it two-way, and document topic, date, leader, and attendance.
- A pre-task plan is redone every day to catch what changed: weather, new trades, new work area, new equipment, and new people.
- OSHA's General Duty Clause plus 1926.20 and 1926.21 require assessing hazards and instructing workers; falls are roofing's top killer among the Focus Four.
Roofing
- OSHA 1926.25 requires scrap with protruding nails and all debris kept cleared from work areas, passageways, and stairs, with combustible scrap removed at regular intervals.
- A hole is defined as a gap of 2 inches or more in its least dimension in a walking or working surface; skylights count as holes.
- Floor-hole covers must be secured against displacement, rated for the load, and marked HOLE or COVER; falls through holes over 6 feet need a cover, guardrail, or fall arrest (1926.501).
- Clean as you go beats the Friday blitz: the person who makes the mess clears it during the task, and it is everyone's job, not the cleanup crew's.
- Route cords and hoses overhead or along walls; cover or ramp lines crossing paths, pull damaged cords from service, and confirm GFCI or assured-grounding (1926.416).
Codes OSHA 1926.25, OSHA 1926.416, OSHA 1926.501, 29 CFR 1910
Roofing
- Referrals and repeat customers are the cheapest leads and close several times better than cold paid leads, so work them first.
- Respond to web leads within about 5 minutes: doing so makes qualifying a lead roughly 21x more likely than waiting 30, and the average contractor takes around 40 minutes.
- Judge channels by cost per booked job, not cost per lead: LSA leads often run $25 to $80, Google PPC around $90+, competitive roofing markets $150 to $300.
- Most sales take five or more follow-up touches, yet most contractors quote once and never call back, handing the job to whoever follows up.
- FTC rules (in effect since late 2024) ban fake, bought, or incentivized-for-positive reviews, with penalties running into tens of thousands of dollars per violation.
Roofing
- Three things hold a mast climber up: the mast tied to the building within its free-standing limit, the base carrying the load, and the platform within its load chart.
- Erecting and dismantling is the most dangerous phase; use a manufacturer-trained, authorized crew, never remove wall ties out of sequence, and keep fall protection in place.
- Carry only what the posted load chart allows; overloading or piling material on a cantilevered end is the most common cause of mast climber collapse.
- Wind shuts a mast climber down at the manufacturer's limit, commonly 25 to 30 mph (about 12 m/s); netting or sheeting adds sail area and lowers it.
- Mast climbers meet the scaffold definition under OSHA 29 CFR 1926 Subpart L; the consensus standard is ANSI/SAIA A92.9, with operators trained to an IPAF PAL card.
Codes 29 CFR 1926, 29 CFR 1926.450
Roofing
- Metal roof restoration treats rust, repairs fasteners and seams, then coats the roof in place, buying 10 to 20 years versus a tear-off.
- A roof qualifies only if structurally sound with surface rust; metal rusted through, perforated, or with fasteners that no longer hold is a replacement.
- Stop rust before coating: wire-brush to sound metal, apply a phosphoric-acid rust converter, then a rust-inhibitive primer (often around 200 sq ft per gallon per coat).
- Drive, upsize, or cap every backed-out or wallowed fastener; a common move upsizes #12 screws to #14 with an EPDM washer.
- The coating manufacturer's published system and warranty for metal substrates governs the prep, primer, dry mils, and approved applicator.
Codes ASTM D08
Roofing
- Metal roofs split into two families by fastening: concealed-fastener standing seam (nothing pierces the weather surface) and exposed-fastener panels screwed through the face.
- Standing seam lasts 40 to 60 years because clips let panels float; exposed-fastener panels run 20 to 30 years before the gasketed washer holes wallow out and leak.
- Standing seam mechanically double-locked seams go lowest, toward 1/2/12 to 2/12; snap-lock, exposed-fastener, and metal shingles want about 3/12 and up.
- Gauge: 29 for budget/ag panels, 26 common residential exposed-fastener, 24 standard for standing seam and high wind, 22 for heavy commercial; lower number is thicker.
- PVDF (Kynar) holds color with 30 to 40 year paint warranties (AAMA 2605); SMP fades sooner at 20 to 25 years; the manufacturer governs slope, gauge, and warranty.
Codes ASTM E1592, ASCE 7, SMACNA, UL 580
Roofing
- Modified bitumen is an asphalt sheet membrane reinforced with polyester or fiberglass and modified with SBS rubber or APP plastic, installed in multiple plies.
- SBS can be torched, hot-mopped, cold-applied, or self-adhered and suits cold climates; APP is almost always torch-applied and suits hot, high-UV climates.
- A bead of bitumen squeezed out at the lap proves the seam fused; for SBS the common target is roughly 3/8 in of flow, less means too little heat.
- Torch jobs need a CERTA-trained applicator and a post-job fire watch, commonly about two hours, since torch fires usually start after work stops; never torch to a combustible substrate.
- Hot-asphalt mopping holds the asphalt within the EVT window, commonly EVT plus or minus 25 degrees F, measured at the point of contact, with a floor of EVT or about 400 degrees F.
Roofing
- Base flashing should extend at least 8 in above the finished roof surface, measured from the finished surface not the deck, with 12 in or more in high-snow regions.
- Counterflashing must lap over the top of the base flashing, commonly 3 to 4 in of overlap, never tuck behind it.
- Sealant is a backup, not the system: a parapet detail must shed water by its shape and still work the day every sealant bead fails.
- Carrying base flashing too low is the most common parapet failure, letting ponding or drifted snow sit above the sealed top and run behind it.
- Masonry parapets need through-wall flashing with weep holes spaced about 24 in on center, plus prefabricated reinforced corners; manufacturer details, NRCA, SMACNA, and the AHJ govern heights and laps.
Codes SMACNA
Roofing
- The 4 to 1 rule sets an extension ladder base out 1 foot per 4 feet of working height, about 75 degrees.
- A ladder reaching a roof must extend about 3 feet above the eave, with the top tied off and base secured.
- Three points of contact means two hands and one foot, or two feet and one hand, on the ladder while climbing.
- Use non-conductive fiberglass ladders anywhere near electrical, including overhead service drops; aluminum and wet wood conduct.
- Match duty rating to worker plus tools: ANSI Type IAA 375 lb, IA 300, I 250, II 225, III 200; Type IA or IAA for roofing.
Codes ANSI A14, OSHA 1926.1053
Roofing
- The IBC allows no more than two roof coverings; once a roof carries two, the next reroof must be a full tear-off to the deck.
- The IBC bars a roof recover over water-soaked insulation or a deteriorated deck; cut out limited wet areas first or strip the whole roof.
- A moisture survey, by infrared or nuclear scan confirmed with core cuts, decides whether a recover is legal before recover or tear-off is chosen.
- A recover fastener must reach through the old roof to the deck or structure; fastening only into old insulation lets wind peel the whole assembly.
- On a tear-off, never open more deck than the crew can dry in before the day ends or weather turns; rain on an open deck has no clean fix.
Codes IBC, IRC
Roofing
- Roof asset management tracks every roof as a capital asset with an inventory, condition rating, remaining-life estimate, and a multi-year capital plan.
- Roof condition index runs 0 to 100: 70-100 repair, 50-70 restore or repair, 30-50 restore or replace, below 30 replace.
- Run a moisture survey before any restore-or-replace decision or recover; coating over wet insulation seals water in and fails early.
- Building codes commonly cap a roof at two membrane layers, so a roof already recovered once usually needs a full tear-off.
- Prioritize spend by condition and consequence together, not worst-first; a poor roof over critical contents outranks a poor roof over low-value space.
Codes ASTM C1153, ISO 55000
Roofing
- Attic ventilation is balanced intake low at the soffit and exhaust high at the ridge; intake net free area must equal or exceed exhaust.
- Base code ratio is 1 sq ft net free vent area per 150 sq ft of attic floor; 1:300 is allowed with a warm-side vapor retarder or a balanced high/low split.
- Never mix two exhaust types on one attic; ridge plus gable or ridge plus power fan short-circuits the flow and leaves dead zones.
- Size by rated net free area in square inches, not the size of the hole cut, because screens and louvers block much of the opening.
- Air sealing and insulation of the ceiling come before ventilation; a vented attic over a leaky ceiling still grows frost and mold.
Roofing
- Dry film thickness equals wet film thickness times percent solids by volume; for 20 dry mils at 92% solids, apply about 22 wet mils.
- Theoretical coverage equals 1604 times percent solids by volume divided by target dry mils, in square feet per gallon.
- Warranty terms tie to dry mils: roughly 20 mils for 10 years, 25 mils for 15 years, 30 mils for 20 years; confirm per product.
- Silicone tolerates ponding water; acrylic is water-based and breaks down under standing water, so use acrylic only on draining roofs.
- Order gallons against practical coverage, not theoretical: spray loses 15 to 30 percent, roller or squeegee 5 to 10 percent.
Codes ASTM D4414, ASTM D6083, ASTM D6694
Roofing
- A roof restoration coating is a fluid-applied membrane that renews an aging but sound low-slope roof without a tear-off; it cannot fix wet insulation or a failed assembly.
- Only silicone tolerates ponding water; it is typically specified around 40 dry mils there, while water-based acrylic softens and breaks down under standing water.
- Run a moisture survey with core cuts first; wet sections up to about a quarter of the roof get cut out and replaced, beyond that the call is a tear-off.
- Always pull an adhesion test patch before the field coat: coating that tears and stays stuck means a good bond; clean substrate means the adhesion failed.
- Warranties run 10 to 20 years tied to dry mils and a closeout inspection; going thin to stretch the pail voids the warranty for the whole roof.
Codes ASTM D08, ASTM D6083, ASTM D6694
Roofing
- The industry and code minimum slope for a low-slope roof to drain is 1/4 in per ft, about 2 percent, toward the drains.
- Roof crickets are sloped steeper than the field, commonly double, so the diagonal valleys stay above the drainage minimum.
- Ponding is standing water remaining more than 48 hours after rain; most membrane warranties require positive drainage and exclude ponding.
- Every drain on a tapered roof gets a sump, a recessed tapered area, so water reaches the drain bowl instead of ringing it.
- Recent IECC editions require above-deck tapered insulation at least 1 in thick at its lowest point, at the drain or scupper.
Codes ASHRAE 90.1, ASCE 7, IBC, IECC, IRC
Roofing
- The roof deck type decides fastening method, assembly fire rating, and the wind uplift path, so confirm it before bidding.
- The six common decks are steel, structural concrete, lightweight insulating concrete, gypsum, wood or plywood, and cementitious wood fiber.
- The concrete 28-day mark is a strength milestone, not dryness; install a low-perm vapor retarder, on the order of under 0.01 perm, over a new slab.
- Steel fastens with screws into the top flute, not the valley; lower gauge means thicker steel, and pullout more than doubles from 26 to 18 gauge.
- Gypsum, lightweight concrete, and wood fiber are nailable only with auger or base-sheet fasteners, often pre-drilled; field-test pullout per ANSI/SPRI FX-1.
Codes ASCE 7
Roofing
- Low-slope roofs need two independent drainage systems: a primary sized for the design storm and a secondary overflow set about 2 in above the low point.
- Roof drain flow Q in gpm equals 0.0104 times drainage area (sq ft) times design rainfall rate (in/hr); pick leader size from IPC tables.
- Rain load R equals 5.2 times (static head plus hydraulic head) in psf; one inch of water weighs about 5.2 psf.
- Use the 100-year design rainfall in in/hr; pull NOAA Atlas 14 and design to the higher of it and the code map.
- Overflow scuppers are sized larger, commonly 3x the roof drains, with a minimum 4 in opening height, and must discharge separately above grade.
Codes ASCE 7, IBC, IPC, IRC
Roofing
- ANSI/SPRI/FM 4435/ES-1 is the national standard governing wind design and testing of low-slope roof edge metal: fascia, gravel stops, and coping.
- ES-1 uses three pull tests: RE-1 (membrane restraint, plf), RE-2 (fascia/gravel-stop outward face load, psf), RE-3 (coping upward and outward, psf).
- Corner-zone wind suction often runs two to three times the field uplift, so corner edge metal must be rated for the corner pressure, not the field.
- A continuous cleat is required: the hemmed drip locks over a hooked strip to carry uplift along the full edge instead of face screws loaded in withdrawal.
- Coping must slope and drain to the roof side, anchor on both faces, and use floating splice-plate joints; expansion joints run ~20-30 ft aluminum, ~40-50 ft steel.
Codes ASCE 7, ASCE 7-10, ASCE 7-16, IBC
Roofing
- A roof expansion joint is built on two raised curbs with the membrane flashed up each side and a flexible bellows cover spanning the gap, never a flat membrane joint.
- Each curb anchors to its own side of the structural gap and stands at the common 8 in minimum base-flashing height so the cover sits above the water.
- Area dividers on attached and adhered systems commonly space every 150 to 200 ft between structural expansion joints; confirm against the membrane manufacturer.
- Water must never drain across or pond against an expansion joint; the raised curbs plus a cricket keep the joint a high point that sheds both ways.
- The membrane manufacturer's detail and warranty govern the cover, flange, and curb height, while the structural engineer sets the joint location and movement rating.
Codes ASCE 7, SMACNA
Roofing
- OSHA requires roof fall protection at 6 feet above a lower level in construction (1926.501) and 4 feet in general industry (1910.28).
- Follow the hierarchy: eliminate the hazard first, then guardrails, then nets or personal fall arrest, then warning line plus monitor for low-slope work.
- A fall arrest anchorage must support at least 5,000 pounds per worker, or be engineered to a safety factor of two; a vent or conduit is not an anchor.
- Construction guardrails need a 42 inch top rail (plus or minus 3 inches) that withstands 200 pounds of force without deflecting below 39 inches.
- A prompt rescue plan must exist before the fall, because suspension trauma can begin in minutes; any component that arrested a fall is retired.
Codes OSHA 1926.501, OSHA 1926.502
Roofing
- Most roof leaks occur at flashings, terminations, and penetrations, not the open field, per NRCA and the trade; chase the detail uphill of the stain.
- Every flashing obeys one rule: each piece laps over the one below so water sheds over a joint, never into it; a reversed lap builds a funnel.
- A watertight wall or curb needs both base flashing (roof material turned up) and counterflashing (the metal cap over it); base height is commonly 8 in low-slope, 4 in steep-slope.
- Residential code requires a cricket or saddle on any chimney wider than 30 in across the slope; the trade commonly recommends one at 24 in.
- Caulk is a backup, not flashing; sealant shrinks and fails in a few seasons, so the flashing must shed water by its shape and laps.
Codes SMACNA
Roofing
- A roof hatch needs three things at the opening: a permanent railing on open sides, a self-closing gate at the ladderway, and a grab bar or safety post.
- New fixed ladders over 24 ft require a ladder safety system or personal fall arrest system, not a cage, under OSHA's updated general-industry rules.
- Roof edge protection scales by distance: within 6 ft always conventional protection, 6 to 15 ft a designated area with warning line for infrequent temporary work.
- A draped chain across the ladderway gap does not satisfy OSHA's self-closing-gate requirement.
- Roof hatches leak at the curb flashing, not the cover, most often at the corners and hinge side where the membrane terminates.
Codes IBC, 29 CFR 1910
Roofing
- Polyiso runs about R-5.6 to 6.5 per inch rated at 75F but falls toward R-4.5 per inch when cold, so design cold climates near R-5, not the warm label.
- Recent IECC editions require insulation in two or more layers with edge joints staggered between layers to break the thermal and air path.
- Above-deck continuous insulation commonly targets about R-20 in hot zones 1 to 2, R-25 in mixed zones 3 to 5, and R-30 in cold zones 6 to 8.
- Metal fasteners running through the full thickness cut effective assembly R by roughly 10 to 30 percent; fasten the base layer and adhere the rest to bury the heads.
- FM Global and UL approve the assembly as a whole; substituting any component voids the listing and the manufacturer warranty, so build to the approved-assembly sheet.
Codes ASHRAE 90.1, ASTM C1289, ASTM C1303, ASTM C578, ASCE 7, IECC
Roofing
- Roof leaks almost never start in the open field; they enter at details: flashings, penetrations, curbs, drains, seams, and terminations.
- Water travels along the deck before it drops, so the entry is uphill of the interior stain, often ten or twenty feet away, never below it.
- Run a hose test in small zones, roughly 6 ft by 6 ft, starting at the lowest point and working uphill with a spotter watching the stain inside.
- Per NRCA, ponding is water remaining on the roof 48 hours or more after rain; roofs are commonly built to drain at 1/4 in per foot.
- All-winter, summer-free, evenly-spread dampness with fastener rust is condensation, not a leak; the fix is ventilation and humidity control, not roofing.
Roofing
- NRCA guidance: inspect a commercial roof at least twice a year, in spring and fall, plus after any major storm.
- Nearly every manufacturer system warranty, including No Dollar Limit, requires documented maintenance and inspection or the claim can be denied.
- Clearing drains, strainers, scuppers, and gutters is the single most important and most neglected low-slope maintenance task.
- Ponding is water standing more than about 48 hours after rain, a warranty exclusion that accelerates membrane aging.
- Repair with the manufacturer's membrane-specific materials by an approved applicator: a TPO puncture needs a welded TPO patch, not generic sealant.
Codes ASTM C1153
Roofing
- One roofing square equals 100 square feet of sloped roof area; divide total roof area by 100 to get squares.
- Apply the slope factor to the footprint: about 1.054 at 4:12, 1.118 at 6:12, and 1.414 at 12:12.
- Add 10 to 15 percent waste: near 10 percent on a simple gable, 12.5 to 15 percent on hip roofs with valleys, 15 to 20 percent on cut-up roofs.
- Three bundles cover one square for standard architectural and three-tab shingles; heavier premium and impact-rated lines run four or five bundles per square.
- Nails run about 320 per square for four-nail shingling and about 480 per square for six-nail high-wind shingling.
Roofing
- Base flashing should turn up at least 8 in above the finished roof, the long-standing NRCA minimum, climbing to 12 in or more in heavy-snow country.
- 80 to 90 percent of commercial roof leaks occur at flashings and penetrations, not the open field; curbs lead, drains are second.
- Flash a round pipe with a prefab boot first, a field wrap second, and a pourable sealer pocket only as a last resort.
- A pourable sealer pocket is the highest-maintenance detail on the roof; its sealant shrinks below the rim and must be topped off on a schedule.
- Hot pipes need a high-temp boot: silicone handles roughly 400 degrees F continuous versus EPDM's roughly 212 degrees F; the manufacturer's detail governs.
Codes SMACNA
Roofing
- NRCA 48-hour rule: a low-slope roof should have no standing water 48 hours after rain in drying weather, or it is ponding.
- Ponded water weighs about 5.2 lb per square foot per inch of depth, the same constant used in the ASCE 7 rain-load equation.
- Many membrane warranties exclude ponding or require drainage within a set time, so a chronic pond can void coverage before it leaks.
- NRCA recommends a minimum design slope of 1/4 in per ft toward drains for low-slope membrane roofs.
- Check blocked drains first, then read pond location: at a drain means slope (tapered insulation); at midspan means structural deflection (engineer).
Codes ASCE 7
Roofing
- A vapor retarder slows vapor diffusion (rated in perms); an air barrier stops bulk air leakage (rated in cfm per square foot at test pressure).
- Air leakage moves roughly 100 times more water than diffusion: a 4x8 sheet passes about a third of a quart per heating season, a 1 inch hole about 30 quarts.
- In cold climates the vapor retarder goes on the warm interior side of the insulation, at deck level, so insulation above keeps it above dew point.
- NRCA suggests a vapor retarder when the coldest month averages below 40F and winter interior humidity is 45 percent or higher, and in Climate Zones 6A, 7, and 8.
- Energy code (ASHRAE 90.1 and IECC) mandates a continuous roof air barrier; deemed-to-comply material air permeance is 0.004 cfm per square foot at 0.3 in. w.c.
Codes ASHRAE 90.1, ASTM E2178, ASTM E2357, ASTM E96, IECC
Roofing
- An NDL (no-dollar-limit) warranty is the strongest commercial coverage, paying full material and labor to fix a covered defect with no cap.
- NDL and system warranties issue only when a manufacturer-certified contractor installs an approved system and the manufacturer's inspector signs off.
- Material-only warranties pay no labor and are usually prorated (often after year 5 or 10), so the owner covers most of any repair.
- Warranties are not insurance: storm, hail, and high wind are excluded acts of god and go to the property insurer, not the manufacturer.
- Unauthorized rooftop work, skipped maintenance, ponding past about 48 hours, and late leak reports (often past 30 to 60 days) void coverage.
Roofing
- Slope decides the family: low-slope below roughly 2:12 needs a continuous membrane, steep-slope above roughly 3:12 to 4:12 sheds with overlapping materials.
- Steep-slope coverings are shingle, metal, tile, slate, and wood; low-slope systems are single-ply (TPO/EPDM/PVC), built-up, modified bitumen, and SPF.
- Confirm the slope minimum against NRCA, the manufacturer's printed instructions, and the adopted code; NRCA recommends 4:12 or steeper for shingle, tile, metal shingle, slate, and wood.
- Steep roofs leak at laps, nails, valleys, and flashing; low-slope roofs leak at seams, terminations, and penetrations, almost never in the open field.
- Verify the structure can carry the dead load before specifying tile (6 to 15 lb/sq ft), slate, ballast, or a green roof; weight gates the choice before aesthetics.
Codes ASCE 7, IBC, IECC, IRC
Roofing
- Roofing underlayment is the layer between deck and covering, serving as the secondary water barrier and the temporary dry-in; the three types are asphalt felt, synthetic, and self-adhered membrane.
- Self-adhered membrane is waterproof and seals around fasteners; felt and synthetic only shed water and leak at fastener holes when water stands.
- Ice and water shield goes at eaves, valleys, penetrations, and low-slope sections, commonly reaching at least 24 inches inside the exterior wall line per code.
- Fasten underlayment with cap nails or cap staples, not bare staples, often about 6 inches at laps and 12 inches in the field with a roughly 1 inch cap.
- Slope drives the underlayment: single layer at roughly 4:12 and up, double layer at 2:12 to 4:12 for shingles, low-slope membrane below about 2:12.
Codes ASTM D1970, ASTM D226, ASTM D4869, ASTM D6757, ASTM D8257
Roofing
- Preferred rooftop support is non-penetrating: flat-bottomed rubber blocks, sleepers, or stands carrying load on top of the membrane with no hole to leak.
- Rooftop block systems publish a per-base load and maximum spacing, commonly several feet up to about 10 ft on center; space for the filled pipe, not empty.
- Put a compatible protection pad or slip sheet, commonly EPDM, TPO, or PVC at 45 or 60 mil, under every load-bearing support.
- Use roller or glide supports on long hot and cold lines, with fixed anchors only where the pipe should not move per the engineer.
- Adding supports, penetrations, or solar without the manufacturer's written approval is a common way the roof warranty gets voided.
Roofing
- Roof maintenance on an existing building falls under OSHA general industry 1910 Subpart D, where fall protection triggers at 4 feet, not the 6 feet of construction 1926.
- Work the hierarchy in order: eliminate the hazard, then passive guardrails, then travel restraint, then fall arrest as the last resort.
- OSHA 1910.29 guardrails commonly run a 42 inch top rail with a midrail and must withstand 200 pounds of force outward or downward.
- A fall arrest anchorage must hold at least 5,000 pounds per worker, or be engineered to a safety factor of at least two.
- Roof anchors get a pre-use check plus a documented annual inspection by a competent person, with longer load-tested recertification by anchor type.
Codes ANSI Z359, OSHA 1910, OSHA 1926, 29 CFR 1910
Roofing
- A PV array lasts about 25 years, so match the roof's remaining life first: re-roof before mounting if the roof has under about five years left.
- Land each lag screw in the center third of the rafter at the manufacturer's embedment depth, or the attachment can pull through under wind uplift.
- Flash every penetration into the water path, upslope edge tucked under the course above, and pull existing shingle nails so the flashing seats; sealant is only a backup.
- Standing-seam metal takes a non-penetrating seam clamp matched to the seam profile, so no holes and no flashing to leak.
- Set slip sheets or protection pads under every ballasted rack foot, and confirm the structural and ASCE 7 wind design (worst at edges and corners) with a licensed engineer.
Codes ASCE 7, IFC, NEC 690, NEC 690.12
Roofing
- The water-resistive barrier and the flashing keep the wall dry, not the siding; water always gets behind the cladding, so the WRB must drain it out.
- Lap the WRB shingle-style, upper over lower, and integrate every flashing into it the same way; reverse-lapping makes a dam that collects water.
- Kick-out flashing is the most-missed detail; install it at every roof-eave-to-sidewall intersection or roof runoff rots the wall behind the siding.
- Hang vinyl loose: nail centered in the slot, leave about 1/32 in under the head, since vinyl moves about half an inch over 12 ft with temperature.
- Cutting fiber cement releases respirable silica (OSHA 29 CFR 1926.1153); use score-snap, shears, or a dust-collecting saw on a vacuum, never a bare dry saw.
Codes ASTM D226, ASTM E2556, IRC, OSHA 1926.1153, 29 CFR 1926.1153
Roofing
- The four single-ply attachment methods are mechanically attached, fully adhered, induction-welded, and ballasted, each carrying a tested uplift rating that must match the design wind load.
- Wind suction is highest at corners, often 2 to 3 times the field pressure, so corners and perimeter get tighter fastening or more adhesive than the field.
- FM Approvals rates assemblies by tested resistance (1-60 held 60 psf, 1-90 held 90, 1-120 held 120) and applies a safety factor of 2.
- Ballasted single-ply per ANSI/SPRI RP-4 caps at a 2 in 12 slope, commonly 10 psf of stone in the field and about 20 psf at the perimeter.
- Pull-test fasteners in the actual deck per FM DS 1-52 to back out the fastener count; never trust a catalog pullout, especially on recovers or aged decks.
Codes ASCE 7
Roofing
- On single-ply roofs the seams, flashings, and penetrations leak, not the field, so seam QC is the roof QC.
- TPO and PVC seams are hot-air welded into one fused material; EPDM is seamed with butyl splice tape and primer.
- A finished hot-air weld is commonly specified at a minimum 1.5 in of fused width, with about 1/8 in squeeze-out bead.
- Pull a daily trial weld each morning and at every condition change; it must show film-tearing bond, where the sheet tears before the seam opens.
- Probe every lineal foot of seam with a blunt tool only after the weld has cooled at least 20 minutes.
Codes ASTM D4434, ASTM D4637, ASTM D6878, ASCE 7
Roofing
- Skylights leak at the flashing and curb, almost never at the glass; the seam where the unit meets the roof is the leak path on most callbacks.
- On low-slope and flat roofs, set the skylight on a curb that gives base flashing at least 8 in of turn-up above the finished roof.
- Code (around R308.6.8) allows a 4 in curb on slopes below 3 in 12, but that 4 in is a floor; manufacturer detail and warranty govern and often require more.
- Build a cricket or saddle on the upslope side of any wide unit; trade practice calls for one on penetrations wider than about 30 in across the slope.
- OSHA treats an unprotected skylight as a hole, requiring protection at 4 ft (1910.28) or 6 ft (1926.501); glazing is not a fall-rated cover.
Codes IBC, NFPA 204, UL 793
Roofing
- Natural slate roofs last 75 to 150 years, but slate roofs fail at the flashings, fasteners, or slates cracked by foot traffic, not the stone.
- Fasten slate with copper or stainless steel only, two nails per slate, set flush so the slate hangs and floats; galvanized rusts out and corrodes against copper.
- ASTM C406 grades slate by service life: S1 over 75 years, S2 40 to 75 years, S3 20 to 40 years; S1 is the new-roof standard.
- Slate weighs 8 to 15 lb per square foot and a slate system often needs framing engineered for 27 to 50 lb per square foot; verify the structure before reroofing.
- Slate is generally not laid below 4:12 slope; standard headlap is 3 in (4 in on lower slopes), and exposure equals (slate length minus headlap) divided by two.
Codes ASTM C406
Roofing
- Snow retention holds the snowpack on the roof so it melts and sheds slowly instead of releasing all at once as a rooftop avalanche.
- Pad guards suit lighter snow and a moderate slope; continuous rails hold heavy snow and steep slopes; many roofs combine a rail at the eave with upslope rows.
- On a standing seam roof use a non-penetrating clamp that grips the seam with set screws, adding no holes; torque the set screw to the manufacturer's value.
- Get a stamped layout from the manufacturer sized to the design snow load, slope, and roof length; never guess the spacing.
- Snow guards do not prevent ice dams, which are a heat-loss problem fixed by air sealing, insulation, and ventilation; holding snow over the eave can make dams worse.
Codes ASCE 7, ASCE 7-22
Roofing
- A solar-ready roof reserves four things at design: structural capacity, a clear unshaded zone, a conduit pathway to electrical space, and a roof and warranty matched to the array.
- A flush attached PV array commonly adds 3 to 5 psf dead load; ballasted systems are heavier, reaching double digits at corners and perimeter where wind uplift is worst.
- Match the membrane and warranty to the 25 to 30 year PV service life, or a tear-off gets built in under a live array.
- Keep the warranty by using the membrane manufacturer's approved attachment, a certified applicator for penetrations, and a written warranty rider before work starts.
- NEC 690.12 requires rapid shutdown, ASCE 7 sets the wind and dead loads, and the IFC sets fire access setbacks; the engineer and adopted code govern the numbers.
Codes ASCE 7, IBC, IECC, IFC, NEC 690, NEC 690.12
Roofing
- An SPF roof is closed-cell foam sprayed as a monolithic, self-flashing, insulating surface, then covered with an elastomeric coating for UV protection.
- Bare SPF foam has no UV resistance and erodes if left uncoated, so a coating plus recoat every 10 to 15 years is mandatory.
- Closed-cell roofing foam cures to 2.5 to 3 lb per cubic foot and adds about 6 to 7 R-value per inch, mixed 1:1 by volume.
- Keep the substrate at least 5 degrees F above the dew point, above about 50 F, humidity below 85 percent, wind under 12 to 15 mph.
- Spray foam in lifts of about 1/2 to 1 inch per pass; acceptable surface texture is smooth or orange peel, never popcorn.
Codes ASTM C1029, ASTM D2842, ASTM D4414, ASTM D6083, ASTM D6694, ASTM E108
Roofing
- Standing seam locks panel seams above the water line over concealed clips, so no fasteners pierce the panel face; these roofs commonly last 40 to 60 years.
- Panels must float: anchor each panel at one fixed point and let floating clips slide everywhere else. Pinning both ends buckles and oil-cans the panel.
- Steel roughly 30 ft long moves about 1/4 in over a 90 degree F swing, and aluminum moves nearly double that.
- Snap-lock panels generally need at least 3/12 slope; mechanically seamed panels go down toward 1/2/12 to 2/12, and below about 2/12 to 3/12 many manufacturers require continuous in-seam sealant.
- Oil canning is cosmetic waviness, not a leak, and no manufacturer warrants against it; clip spacing tightens at corners and edges for wind uplift per the tested assembly (UL 580/90, FM, ASTM E1592, ASCE 7).
Codes ASTM E1592, ASCE 7, SMACNA, UL 1897, UL 580
Roofing
- Asphalt shingles shed water rather than seal it, so the standard minimum slope is 4:12; the 2:12 to under-4:12 range needs double underlayment or a self-adhered membrane, and below 2:12 use a membrane roof.
- Use 4 nails per shingle for standard installs and 6 in high-wind zones (commonly above 110 mph), driven flush in the marked nail line so each fastener holds two courses.
- Overdriven nails are the number-one field shingle failure: the head crushes or cuts the mat and stops holding; fix by setting gun pressure and hand-nailing the bad ones.
- Ice and water shield goes at eaves, valleys, and penetrations, reaching past the inside face of the exterior wall, commonly at least 24 in inside that warm wall line.
- Eave drip edge goes under the underlayment and rake drip edge over it; balance attic ventilation so intake meets or exceeds exhaust at a net free area of 1 sq ft per 150 sq ft of attic.
Codes ASTM D1970, ASTM D226, ASTM D3161, ASTM D3462, ASTM D8257, UL 2218
Roofing
- Real hail damage fractures the shingle mat under the granules and feels soft to the touch; surface marking with no mat fracture is cosmetic and often policy-excluded.
- Chalk a 10 ft by 10 ft test square on each slope, count and mark the hits, and inspect soft metals first because dents confirm the storm.
- A contractor cannot legally waive, eat, or rebate the deductible; offering to cover it is insurance fraud and a crime in states like Texas and Colorado.
- Date of loss is the verified storm date from NOAA or a hail-map service, not the discovery date; without it carriers can call damage old wear.
- Negotiating, interpreting coverage, or settling a claim is public adjusting, licensed in most states; contractors assess and build, then refer disputes to a public adjuster or attorney.
Roofing
- OSHA Subpart L requires supported scaffolds to support their own weight plus at least 4 times the maximum intended load.
- Guardrails (top rail, mid rail, toeboard) are required on open sides and ends more than about 10 feet above a lower level.
- Scaffold legs must bear on base plates and mud sills; blocks, bricks, and lumber scraps are prohibited as support.
- Tie a supported scaffold to the structure once its height-to-base ratio passes 4 to 1, repeating ties up the height.
- A competent person with authority to red-tag must inspect the scaffold before each shift and after any storm or change.
Codes 29 CFR 1926
Roofing
- Each worker on a suspended scaffold ties off to a separate, independent vertical lifeline on its own anchor, never to the platform, its outrigger beams, or counterweights.
- OSHA Subpart L (29 CFR 1926.451) requires counterweights to resist at least four times the tipping moment, using only items made and marked as counterweights, plus a tieback equal in strength to the suspension ropes.
- Suspension ropes and components must support at least six times the maximum intended load, and a competent person inspects the wire rope before every shift.
- A wire rope is removed for six broken wires in one lay, three broken wires in one strand, kinks, or loss of over one-third of outside-wire diameter to abrasion or corrosion.
- Suspension hoists need a secondary brake that engages automatically on overspeed, and a site-specific rescue plan must be ready before anyone goes over the parapet to prevent suspension trauma.
Codes 29 CFR 1926
Roofing
- The underlayment, not the tile, is the actual waterproofing on a tile roof; leaks almost always come from the underlayment or a flashing, not the tile.
- Tile weighs 6 to 12 lb per square foot (about 600 to 1,100 lb per square), so a structural engineer must verify the framing carries the dead load before tear-off.
- Spec a high-temperature, tile-rated underlayment; tile traps heat that cooks a standard ice-and-water shield until it flows.
- Clay and concrete tile install on 2.5:12 and steeper, with enhanced or doubled underlayment required between 2.5:12 and 4:12.
- Walk the lower third of each tile at the headlap where it is supported, never the nose or center; clay breaks more readily than concrete.
Codes IBC, IRC
Roofing
- No single low-slope membrane is best: PVC resists grease/chemicals, EPDM leads on longevity and cold flex, TPO is the reflective mid-cost option.
- For restaurant or grease roofs specify PVC; TPO commonly fails in 8-12 years and EPDM rubber degrades from cooking grease too.
- TPO and PVC are thermoplastics with hot-air-welded seams; EPDM is thermoset rubber seamed with butyl splice tape and primer.
- PVC is incompatible with asphalt and mod-bit; recovering over them requires a separator slip sheet or cover board between the two.
- Membrane comes in 45, 60, and 80 mil; thickness ties to warranty term, and installing thin can void the manufacturer's NDL warranty.
Codes ASTM D4434, ASTM D4637, ASTM D6878, ASCE 7
Roofing
- A traffic coating is corrosion protection for the deck, keeping water and chlorides out of the structural concrete so the rebar does not corrode.
- The system layers in fixed order: primer, crack-bridging base coat (the waterproofing), silica-sand aggregate broadcast for traction, then top coat.
- Typical dry mils exclusive of aggregate run about 20 to 35 for pedestrian and 40 to 55 for vehicular, per the data sheet.
- Prep concrete by shot blasting or grinding to ICRI CSP 3 to 4, removing all laitance, curing compound, and contamination.
- Test concrete moisture (ASTM F2170, F1869, or D4263) to the manufacturer limit; a wet or green slab delaminates the coating via vapor drive.
Codes ASTM C957, ASTM D4263, ASTM F1869, ASTM F2170
Roofing
- Two governors decide a cedar roof: the wood must breathe (dry from both faces) and resist fire, since untreated cedar is combustible.
- A wood shake is split (thick, 1/2 in to 3/4 in at the butt); a wood shingle is sawn (thinner, 0.40 in to 0.45 in); shakes use interlayment felt, shingles do not.
- Use stainless steel Type 304 or 316, or hot-dip galvanized nails only; cedar tannins corrode electro-galvanized and bright nails, which then stain and loosen.
- Common minimum slope is 4:12, with reduced exposures down to about 3:12; a maintained cedar roof commonly lasts 30 to 40 years or more.
- Leave keyway gaps for swelling (about 3/8 in to 5/8 in shakes, 1/4 in to 3/8 in shingles) and offset joints at least 1-1/2 in so they never align.
Codes ASTM A153, ASTM D226, ASTM D4869, ASTM E108, UL 790