Metal Roofing Installation
Why this matters
Metal roofing is the fastest-growing residential roof segment, 5 - 8% of US market + climbing 8 - 12%/year. Per-square pricing. The customer-perceived premium + 40 - 70 year lifespan justify the price. The risks: thermal expansion, fastener selection, flashing detail. Done well, the roof outlasts the homeowner; done poorly, it leaks within 5 years + the customer + insurance both come after you.
Metal roofing types
Standing seam (premium residential)
- Continuous vertical panels with concealed fastener system at the seam
- Mechanically-seamed OR snap-lock joinery
- 1.5 - 3 inch rib height standard
- Most aesthetically clean; no exposed fasteners
- Best lifespan: 40 - 70+ years
Exposed-fastener (corrugated, R-panel, 5V)
- Screw-down panels with rubber-washered fasteners visible
- Lower cost; faster install
- Lifespan: 20 - 40 years (limited by fastener washer life - 15 - 25 years typical)
- Best for: barns, agricultural, secondary structures, budget residential
Metal shingles (residential decorative)
- Stamped metal in shake / slate / tile-look profiles
- Installed shingle-fashion with proprietary clips
- Premium pricing; specialty manufacturer support
Stone-coated steel
- Steel panel with bonded mineral coating
- Mid-tier residential
Material specifications
Gauge
- 24-gauge: premium; standing seam standard; longest life
- 26-gauge: standard residential; most exposed-fastener
- 29-gauge: budget; agricultural; not recommended for primary residential
Coating
- Galvalume (zinc-aluminum alloy coated steel): industry standard; 40+ year coating life
- Galvanized (zinc coated steel): older spec; shorter coating life
- Aluminum: premium for coastal (zinc galvanizing corrodes in salt spray)
- Copper / zinc: high-end architectural; specialty install
- Paint system: SMP (silicone modified polyester) - 25 - 35 year warranty; PVDF (Kynar 500 / Hylar 5000) - 35 - 50 year warranty; PVDF is the premium standard
Energy Star + cool roof
- Reflective coatings reduce attic temperature 10 - 30°F
- Energy Star rated panels reduce HVAC load 5 - 15%
- IRA energy efficient home tax credit applies to some metal roofing
Pre-install requirements
Roof deck
- Solid sheathing (5/8" OSB or 1/2" plywood minimum)
- Inspect for rot, sag, fastener pull-through
- Replace as needed
- Flat + smooth - bumps telegraph through metal
Underlayment
- Ice + water shield at eaves (minimum 2 ft past wall line per IRC) + valleys + penetrations
- Synthetic underlayment over field (NOT felt - too short-lived under metal)
- High-temp underlayment recommended for metal (rated 240 - 260°F continuous)
Ventilation
- Same NFPA 1:300 ratio as shingles (1 sq ft net free area per 300 sq ft attic floor; ideal balance of soffit + ridge)
- Ridge vent + soffit vent the standard install
- Metal roofing benefits from ventilation more than shingles (thermal cycling reduced)
Flashing materials
- Same gauge + finish as primary panel where possible
- Pre-formed valleys + sidewall flashings preferred over field-cut
- Eave drip with at least 1" overhang
Standing seam install
- Plan + measure: panel length (eave-to-ridge in one piece up to 30 - 40 ft); panel spacing per manufacturer; penetration flashings
- Decking + underlayment: solid sheathing; ice + water at eaves + valleys; high-temp synthetic over field
- Eave + ridge: eave drip with 1"+ overhang; ridge framing prep
- Panel install: first panel squared to gable sets every subsequent; snap-lock OR clip per manufacturer; hidden clips 16 - 24" spacing; NEVER face-fasten panel body
- Mechanical seam: single OR double-fold at each rib (power seamer for double); test seam at each panel
- Flashings: pre-formed pipe boots; step at sidewall in butyl tape; pre-formed valleys; closure foam + ridge cap
- Final: panels straight + seams uniform + no oil-canning; customer walk + photo
Thermal expansion (the often-overlooked constraint)
Metal moves with temperature. Over 30 ft panel length, expect 1/2 - 3/4 inch movement between summer + winter. The system must allow this:
- Hidden clips designed for sliding movement (NOT rigid attachment)
- Through-fastened metal: panels fastened only at eave (top stays free) OR with oversized hole + neoprene-washered screw
- Long panels need engineered expansion provisions
Restraining a metal roof causes oil-canning (visible waviness), seam separation, OR fastener pull-through. The most common metal-roof failure is failure to plan for thermal movement.
Common installation mistakes
Face-fastening standing seam through panel body
- Voids manufacturer warranty
- Creates leak points
- Defeats the purpose of standing seam
Wrong fastener for the material
- Stainless on coastal aluminum (galvanic OK)
- Carbon steel screw with neoprene washer common; check coating compatibility
- Mismatched fasteners corrode + stain panel + fail early
Bypassing ice + water at vulnerable spots
- Valleys + eaves + penetrations carry the highest leak risk
- Ice + water under metal at these locations is non-negotiable
- Skipping to "save money" creates leak chains
Cutting on top of the panel below
- Filings ("swarf") rust on the panel surface + stain immediately
- Cut OFF the roof OR catch all filings on canvas underneath
Walking on panels without protection
- Footprints + dents are PERMANENT in some panel types
- Plank or knee pads to distribute weight
- Walk in the valleys between ribs
NEVER cut metal panels with an abrasive disc on the roof. The filings (called swarf) rain down onto the panel below + every spot of swarf rust-stains the panel within weeks. Customer sees orange polka dots across their new roof + you eat the panel replacement. Cut panels OFF the roof on a sacrificial surface, OR catch ALL swarf with a tarp under the cut. The 5-minute setup prevents the cleanup or panel replacement.
Acceptance criteria
- All panels straight + parallel
- Seams uniform; mechanical-seamed where applicable
- No oil-canning visible at viewing distance
- All penetrations flashed per manufacturer detail
- No exposed fasteners (standing seam)
- All trim installed
- Customer walks + signs
Warranty + insurance
- Manufacturer panel warranty: 25 - 50 years (paint), 30 - 60 years (substrate)
- Installer workmanship warranty: 5 - 25 years
- Insurance carrier inspection often required at completion
- Customer-side: hail + wind ratings affect homeowner premium
References
- Metal Construction Association (MCA) installation guides
- Manufacturer install manuals (varies by panel)
- ASTM A653 (galvanized steel sheet)
- IRC R905.10 (metal roof systems)