1 Scope
NOTE This standard covers the materials, design basis, fabrication, and installation of architectural sheet metal flashing and trim that completes the watertight building envelope at roof edges, parapets, wall penetrations, and material transitions. (1.1)
NOTE The sheet metal addressed here is a system of formed metal pieces — copings, counterflashings, base flashings, gravel stops, fasciae, gutters, downspouts, scuppers, conductor heads, through-wall flashings, head and sill flashings, expansion-joint covers, and closure trim — whose joinery, cleating, hemming, and expansion-joint detailing are designed and installed per the SMACNA Architectural Sheet Metal Manual. (1.2)
NOTE The SMACNA Architectural Sheet Metal Manual is the foundational industry reference for this work; this standard is read together with SMACNA's current edition and does not duplicate the geometric pattern details that the SMACNA manual already provides. (1.3)
NOTE Sheet metal flashing is interface work: most pieces live at the seam between two systems — roof and wall, wall and window, parapet and roof, or an expansion joint between two structural bays — so the performance of every piece depends on the dimensional accuracy of the adjacent construction and on a sequencing plan that places the sheet metal at the correct point in the construction order. (1.4)
NOTE A coping cap that is otherwise correctly fabricated will fail if it is set on out-of-level blocking, undersized for the parapet width, or installed after the membrane base flashing has been cut short on the inside face of the parapet. (1.5)
1.6 The Contractor shall verify dimensions and substrate conditions before fabrication.
1.7 The Contractor shall coordinate sequencing with the roofing, masonry, framing, and cladding trades.
NOTE The roof-edge subset of this work — copings, gravel stops, fasciae, and drip edges — is also wind-design-critical, and IBC Section 1504.5 requires that low-slope roof-edge metal be tested and labeled per ANSI/SPRI ES-1. (1.8)
1.9 Roof-edge metal that does not carry an ES-1 classification meeting the design wind pressure shall not be installed; this requirement is not waivable.
1.10 Where the project's roof is governed by FM Global insurance, FM Approval (FM 4435) for the roof-edge metal is additionally required.
1.11 Copings or edge metal that are field-fabricated on site without an ES-1 listing for the as-built profile and securement shall be either replaced with an ES-1-listed product or engineered and tested for the project conditions before installation.
1.12 Counterflashings, wall flashings, gutters, downspouts, and trim that do not function as roof-edge wind securement are not subject to ES-1 but shall comply with the cleat, fastener, and joint provisions in SMACNA for resistance to wind, thermal movement, and water infiltration.
1.13 The Contractor responsible for this scope shall have prior experience with the specified metal type.
1.14 Soldering of copper, lead-coated copper, and stainless steel shall be performed by trained operators; welding of aluminum and stainless steel shall be performed by qualified welders; and brake-formed shop work in heavier gauges of steel and stainless shall be performed by a fabricator with appropriate brake capacity.
1.15 The Contractor shall identify the fabricator and submit fabricator qualifications as part of the action submittal package.
2 Referenced Standards
NOTE The latest adopted edition of the following standards governs unless a specific edition is cited as controlling by the Authority Having Jurisdiction or the Owner. (2.1)
| Standard |
Title |
| SMACNA Architectural Sheet Metal Manual |
Current edition — foundational reference for joint, cleat, hem, and expansion-joint details |
| ANSI/SPRI/FM 4435/ES-1 |
Wind Design Standard for Edge Systems Used with Low Slope Roofing Systems |
| FM 4435 |
Approval Standard for Edge Systems Used with Low Slope Roofing Systems |
| ASTM A653/A653M |
Standard Specification for Steel Sheet, Zinc-Coated (Galvanized) or Zinc-Iron Alloy-Coated (Galvannealed) by the Hot-Dip Process |
| ASTM A792/A792M |
Standard Specification for Steel Sheet, 55% Aluminum-Zinc Alloy-Coated (Galvalume) by the Hot-Dip Process |
| ASTM A240/A240M |
Standard Specification for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and for General Applications |
| ASTM A480/A480M |
Standard Specification for General Requirements for Flat-Rolled Stainless and Heat-Resisting Steel Plate, Sheet, and Strip |
| ASTM B370 |
Standard Specification for Copper Sheet and Strip for Building Construction (cold-rolled and tempered) |
| ASTM B69 |
Standard Specification for Rolled Zinc |
| ASTM B209/B209M |
Standard Specification for Aluminum and Aluminum-Alloy Sheet and Plate |
| AAMA 2605 |
Voluntary Specification, Performance Requirements and Test Procedures for Superior Performing Organic Coatings on Aluminum Extrusions and Panels (70% PVDF / Kynar 500) |
| AAMA 2604 |
Voluntary Specification, Performance Requirements and Test Procedures for High Performance Organic Coatings on Aluminum Extrusions and Panels (50% PVDF) |
| AAMA 2603 |
Voluntary Specification, Performance Requirements and Test Procedures for Pigmented Organic Coatings on Aluminum Extrusions and Panels (commercial polyester) |
| AAMA 611 |
Voluntary Specification for Anodized Architectural Aluminum |
| ASTM A924/A924M |
Standard Specification for General Requirements for Steel Sheet, Metallic-Coated by the Hot-Dip Process |
| ASTM A153/A153M |
Standard Specification for Zinc Coating (Hot-Dip) on Iron and Steel Hardware (fasteners) |
| ASTM F1667 |
Standard Specification for Driven Fasteners: Nails, Spikes, and Staples |
| ASTM C920 |
Standard Specification for Elastomeric Joint Sealants (urethane, silicone) |
| ASTM D1056 |
Standard Specification for Flexible Cellular Materials — Sponge or Expanded Rubber (closed-cell butyl tape) |
| ASTM E2140 |
Standard Test Method for Water Penetration of Metal Roof Panel Systems by Static Water Pressure Head |
| ASCE 7 |
Minimum Design Loads and Associated Criteria for Buildings and Other Structures |
| IBC |
International Building Code — Sections 1503 (Roof Drainage), 1504 (Performance Requirements), 1505 (Fire Classification), 1503.6 and 1504.5 (Roof Edge Securement) |
| NRCA Roofing Manual |
Membrane Roof Systems (architectural sheet metal flashing details) |
| FGIA (formerly AAMA) |
Standards for architectural finishes and dissimilar-metal isolation |
| SSINA Designer Handbook |
Specialty Steel Industry of North America — Stainless Steel Fabrication and Finishing |
| Copper Development Association — Copper in Architecture Handbook |
Standard reference for copper sheet metal design and detailing |
2.2 Where conflict exists between referenced standards, the more stringent requirement shall govern unless the Designer of Record directs otherwise in writing.
3 Submittals
3.1 Action Submittals
3.1.1 The Contractor shall submit the following for the Designer of Record's review and approval before procuring materials, fabricating sheet metal pieces, or beginning installation.
- Product data sheets for each metal type, confirming the applicable ASTM specification, base-metal thickness or gauge, coating designation (e.g., G90, AZ50), alloy and temper, and finish (mill, prepainted PVDF/SMP, anodized, batch-coated)
- Manufacturer's published finish system data, including AAMA 2605 or AAMA 2604 conformance for prepainted coil and panel, AAMA 611 conformance for anodized aluminum, and warranty terms
- ANSI/SPRI ES-1 test report and listing for each roof-edge profile (coping, gravel stop, fascia, drip edge), confirming the tested wind pressure equals or exceeds the design edge-zone pressure from ASCE 7; FM 4435 approval listing where FM Global insurance governs
- Shop drawings showing each fabricated piece in plan, section, and elevation with dimensions, gauges, joint locations, cleat type and spacing, expansion-joint locations, hem details, and corner geometry; shop drawings shall reference the corresponding SMACNA detail plate where applicable
- Layout drawings showing the location of every shop joint, expansion joint, cleat run, downspout, scupper, and conductor head on the building elevations
- Color samples and finish samples on the actual specified metal substrate, of sufficient size to evaluate color, gloss, and texture in natural daylight; for prepainted coil, a minimum 12 inch by 12 inch sample for each color
- Fabricator qualifications, including past project references for the metal type and joint methods specified
- Sealant compatibility certifications between the specified sealant and the specified metal finish, including any pre-treatment requirements for adhesion to PVDF coatings
- Cut list and yield plan for copper, zinc, and stainless steel scopes, demonstrating that pan widths and seam locations match the SMACNA detail being specified
☐ Product data sheets for each metal type (ASTM spec, gauge, coating, alloy/temper, finish)
☐ Manufacturer's finish system data (AAMA 2605/2604/611 conformance, warranty terms)
☑ ANSI/SPRI ES-1 test report and listing for each roof-edge profile (FM 4435 where required)
☐ Shop drawings (plan, section, elevation; joints, cleats, expansion joints, hems, corners)
☐ Layout drawings (shop joints, expansion joints, cleat runs, downspouts, scuppers, conductor heads)
☐ Color and finish samples on actual specified substrate (12 in x 12 in minimum for prepainted coil)
☑ Fabricator qualifications with project references for metal type and joint methods
☐ Sealant compatibility certifications (including PVDF pre-treatment requirements)
☐ Cut list and yield plan for copper, zinc, and stainless steel scopes
● Required — ES-1 listed product (mandatory for all low-slope roof edge per IBC 1504.5)
○ Required — ES-1 plus FM 4435 approval (FM Global insured projects)
○ Not applicable — sheet metal scope does not include low-slope roof edge
3.1.2 The Contractor shall submit the action submittal items listed above for the Designer of Record's review and approval before procuring materials, fabricating, or beginning installation.
3.1.3 The roof-edge metal submittal shall include current ANSI/SPRI ES-1 test documentation for the as-specified profile, securement, and substrate; without that documentation the submittal is incomplete and shall not be approved.
3.2 Closeout Submittals
3.2.1 The Contractor shall provide the following at substantial completion before the sheet metal work is accepted.
- Manufacturer's written warranty for prefinished coil and panel, covering film integrity, color fade (delta-E units), and chalk per the AAMA 2605 or 2604 finish-warranty schedule
- Fabricator's written workmanship warranty
- Touch-up paint, in the specified color, in sealed factory containers — minimum quantity sufficient for documented field touch-up plus owner attic-stock per the contract documents
- Final marked-up shop drawings showing as-installed expansion-joint locations, all field-cut and field-fitted pieces, and the location of any field repair
- Maintenance instructions for cleaning, periodic inspection, and sealant joint maintenance, prepared by the fabricator or finish manufacturer
☐ Manufacturer's written finish warranty for prefinished coil and panel (film, color fade, chalk)
☑ Fabricator's written workmanship warranty
☐ Touch-up paint in specified color, sealed factory containers, plus owner attic-stock
☐ Final marked-up shop drawings (as-installed expansion joints, field-cut pieces, field repairs)
☐ Maintenance instructions for cleaning, inspection, and sealant joint maintenance
3.2.2 The Contractor shall provide the closeout submittal items listed above at substantial completion before the sheet metal work is accepted.
4 Quality Assurance
4.1 Fabricator Qualifications
4.1.1 The sheet metal fabricator shall have a minimum of five years of documented experience fabricating architectural sheet metal in the metal type, gauge, and finish specified, including shop or field soldering of copper or stainless steel where those metals are required to be soldered.
4.1.2 The fabricator shall have brake and roll-forming capacity adequate for the longest piece on the project.
4.1.3 The Contractor shall submit the fabricator's project list as part of the qualification documentation.
4.2 Installer Qualifications
4.2.1 The installer shall be experienced in architectural sheet metal installation, with documented experience installing ES-1-listed roof-edge metal where that scope is included.
4.2.2 The installer shall coordinate directly with the roofing Contractor where the sheet metal scope interfaces with the membrane assembly.
4.3 Pre-Installation Conference
4.3.1 A pre-installation conference shall be held before sheet metal installation begins.
4.3.2 Attendees shall include the Contractor's sheet metal installer, the roofing Contractor, the mason or wall-cladding contractor, the Designer of Record, and the Owner's representative.
4.3.3 The conference shall cover sequencing with the roofing and wall trades (which membrane base flashings must be in place before counterflashings, which cant strips before coping installation, which through-wall flashings before masonry coursing proceeds), expansion-joint locations, sealant joint design, ES-1 fastener pattern verification, dissimilar-metal isolation, and field cutting and touch-up policy.
4.3.4 Minutes shall be distributed within five business days.
4.4 Mock-Up
4.4.1 Where the project includes prominent visible sheet metal — exposed copings, fasciae visible from grade, custom gutter profiles, or copper or zinc roofing-adjacent flashings — a field mock-up shall be installed for review before production fabrication.
4.4.2 The mock-up shall include at least one corner condition, at least one expansion joint, and at least one termination, and shall be reviewed by the Designer of Record and the Owner before production work proceeds.
4.4.3 Approved mock-ups may remain as part of the finished work if they pass inspection.
5.1 Material Selection — Principles
NOTE Metal selection is driven by the design service life, the visual exposure of the finished surface, the chemistry of the environment (coastal, industrial, urban), galvanic compatibility with adjacent metals, the substrate to which the metal will be fastened, and budget. (5.1.1)
● Prefinished galvanized steel — ASTM A653, G90 coating designation
○ Prefinished Galvalume — ASTM A792, AZ50 or AZ55 coating designation
○ Aluminum sheet — ASTM B209, alloy 3105-H14 or 5005-H14
○ Stainless steel — ASTM A240, Type 304 (interior, mild exterior)
○ Stainless steel — ASTM A240, Type 316 (coastal or corrosive)
○ Copper — ASTM B370, cold-rolled, 16 oz/sf or 20 oz/sf
○ Zinc — ASTM B69, rolled architectural zinc
NOTE Galvanic compatibility is a hard constraint, not a preference: copper in contact with aluminum or galvanized steel, water-borne copper salts washing onto aluminum below, or carbon-steel fasteners in contact with stainless or aluminum sheet will all produce galvanic corrosion that progresses for the life of the building. (5.1.2)
5.1.3 The Designer of Record shall establish the metal type for each piece in the scope.
5.1.4 The Contractor shall not substitute a different metal type or coating without written approval and confirmation that the substitution does not create a galvanic incompatibility.
5.2 Galvanized Steel — ASTM A653
● G90 (0.90 oz/sf total both sides — minimum for exterior architectural use)
○ G60 (not acceptable for exterior; interior or concealed only)
26 ga (0.0217 in — light trim only, short spans)
24 ga (0.0276 in — typical light counterflashing and closure trim)
22 ga (0.0336 in — typical coping, fascia, and gutter)
20 ga (0.0396 in — long spans and high-exposure pieces)
Per SMACNA recommendation for piece type and span
5.2.1 Hot-dip galvanized sheet steel for architectural flashing and trim shall conform to ASTM A653/A653M, with a minimum G90 coating designation (0.90 oz/sf total both sides, triple-spot test).
5.2.2 G60 coating is not appropriate for exterior architectural use and shall not be substituted.
5.2.3 The base steel shall be commercial steel (CS) or forming steel (FS) per ASTM A653 as appropriate for the forming complexity.
5.2.4 The Contractor shall avoid leaving exposed cut edges in locations where water collects; cathodic protection from the adjacent zinc coating mitigates edge corrosion in service but does not eliminate it.
5.2.5 Where bare cut edges are unavoidable, they shall receive a touch-up of cold galvanizing compound (95% zinc, mil-spec compliant) or a compatible primer and finish.
NOTE Galvanized steel is the most cost-effective metal for exterior sheet metal trim on commercial buildings and is the default for non-prominent flashing scopes when finished with a prepainted PVDF or SMP coil coating; bare mill galvanized weathers from a "spangle" pattern to uniform gray over several years, and a prepainted finish is preferred on prominent surfaces. (5.2.6)
5.2.7 The Contractor shall follow the SMACNA gauge tables unless the contract documents specify a heavier gauge; a lighter gauge can result in oil-canning, seam distortion, and reduced longevity, while a heavier gauge increases stiffness at the cost of brake-forming difficulty.
5.3 Galvalume (55% Al-Zn) — ASTM A792
● AZ50 (standard exterior architectural)
○ AZ55 (extended exposure, corrosive environments)
5.3.1 Galvalume sheet steel shall conform to ASTM A792/A792M, with AZ50 (0.50 oz/sf total both sides) coating designation for exterior architectural use, or AZ55 for extended-exposure applications.
NOTE The 55% aluminum-45% zinc coating provides substantially longer service life than G90 galvanized in most exterior environments, but is less effective than galvanized in alkaline contact (mortar runoff, fresh concrete, animal-confinement environments) because the aluminum-rich coating is dissolved by high-pH water. (5.3.2)
NOTE Galvalume is the predominant substrate for prefinished coil used in low-slope roof-adjacent sheet metal and is widely available in PVDF and SMP coil finishes. (5.3.3)
5.4 Aluminum — ASTM B209
○ 3003-H14 (general-purpose formed sheet)
● 3105-H14 (improved corrosion resistance; standard for painted coil)
○ 5005-H14 (preferred substrate for anodized finish)
0.032 in (general flashing and trim)
0.040 in (light coping and fascia)
0.050 in (typical coping, long-span fascia, gutter)
0.063 in (high-exposure coping, large gutter, structural fascia)
0.080 in (custom long-span coping, ornamental)
Per SMACNA recommendation for piece type and span
5.4.1 Aluminum sheet for architectural flashing and trim shall conform to ASTM B209/B209M, using alloy 3105-H14 or 5005-H14 for formed sheet, or 3003-H14 for copings, fasciae, and trim that are not anodized.
5.4.2 5005-H14 is the preferred substrate for anodized finishes; 3105-H14 is general-purpose with good formability.
5.4.3 Aluminum shall not be used in direct, continuous contact with mortar or fresh concrete (alkaline attack), nor in direct galvanic contact with copper or copper-bearing salts.
5.4.4 Where dissimilar-metal contact is unavoidable, isolation per the Dissimilar Metal Isolation section is required.
NOTE Aluminum is light, corrosion-resistant in most atmospheric environments, and the standard substrate for prefinished PVDF coil-coated trim on commercial buildings. (5.4.5)
5.5 Stainless Steel — ASTM A240
● Type 304 — interior or mild exterior atmospheric exposure
○ Type 316 — coastal, chloride-exposed, or de-icing-salt environments
● No. 2B — cold-rolled, annealed, smooth, low-reflectivity (general flashing)
○ No. 4 — brushed satin (visible architectural)
○ No. 8 — mirror polished (specialty visible only; not typical for flashing)
0.0187 in (26 ga — general light flashing)
0.0250 in (24 ga — typical counterflashing and trim)
0.0312 in (22 ga — coping, fascia)
0.0375 in (20 ga — heavy or long-span work)
5.5.1 Stainless steel sheet for architectural flashing shall conform to ASTM A240/A240M, with surface finish per ASTM A480/A480M.
5.5.2 Type 304 (UNS S30400) is the standard architectural grade for interior and mild exterior environments.
5.5.3 Type 316 (UNS S31600), containing molybdenum for improved chloride resistance, shall be specified for coastal environments (within five miles of salt water), de-icing-salt-exposed locations, and pool-area applications.
5.5.4 The standard architectural finish shall be No. 2B (cold-rolled, annealed, smooth, low-reflectivity) for general flashing and trim, or No. 4 (brushed, satin) where a directional appearance is desired on visible work.
NOTE Stainless steel is the most durable common architectural sheet metal in chloride-exposed environments but is the most difficult to form and join — it work-hardens during brake forming, requires larger inside-bend radii to avoid cracking, requires welding rather than soldering in heavier gauges, and is the most expensive common architectural metal. (5.5.5)
5.6 Copper — ASTM B370
○ 16 oz/sf (0.0216 in — light flashing, short spans)
● 20 oz/sf (0.0270 in — typical coping, fascia, gutter; recommended default)
○ 24 oz/sf (0.0323 in — long-span gutter, ornamental, premium service life)
● Mill (bright) — natural weathering to patina
○ Lead-coated copper (architectural lead-tin terne; restricted use under modern lead regulations)
○ Pre-patinated (factory-applied chemical patina, accelerated weathering)
5.6.1 Copper sheet for architectural sheet metal shall conform to ASTM B370, cold-rolled and tempered, with weight specified in ounces per square foot (16 oz/sf approximately 0.0216 in, 20 oz/sf 0.0270 in, 24 oz/sf 0.0323 in).
5.6.2 The Owner shall be informed of the weathering trajectory before specifying copper for prominent surfaces, since copper weathers from bright copper through brown to a stable patina over years to decades and the patinated surface is itself the corrosion-protection layer.
5.6.3 Where copper is installed above a porous surface (limestone, concrete, painted aluminum) that will be visible after weathering, the drip line of the copper shall be detailed to direct water away from the porous surface, or the porous surface shall be protected by an intervening element that takes the staining out of the public view.
5.6.4 Copper shall not be installed in direct galvanic contact with aluminum, galvanized steel, zinc, or steel — including via runoff onto those metals from above.
5.6.5 Copper joints in pieces likely to be soldered (gutters, scuppers, long-run counterflashings) shall be made with lead-free solder per current building-code requirements.
5.6.6 Rosin flux shall be used and shall be neutralized and washed after soldering to prevent corrosion under the solder line.
5.6.7 Soldered joints in heavier-weight copper (20 oz/sf and 24 oz/sf) shall be performed by a soldering operator experienced in the heavier weight, because they require more heat input and slower work than 16 oz/sf.
5.7 Zinc — ASTM B69
0.7 mm (light trim, short runs)
0.8 mm (typical coping, fascia, gutter)
1.0 mm (long spans, heavy-exposure)
5.7.1 Architectural zinc sheet (rolled zinc-copper-titanium alloy) shall conform to ASTM B69, in standard architectural thicknesses of 0.7 mm, 0.8 mm, and 1.0 mm.
5.7.2 All zinc sheet metal shall be installed with a ventilated underside per the zinc manufacturer's published details, because zinc has very low tolerance for stagnant moisture on the underside (white corrosion is a rapidly progressing failure mode).
5.7.3 Zinc shall not be installed over a moisture-trapping underlayment.
5.7.4 Zinc shall not be in direct contact with copper, copper-bearing salts, oak or chestnut tannins, or continuous wet alkaline materials (fresh concrete, mortar).
NOTE Zinc forms a self-healing carbonate patina in atmospheric exposure that protects the underlying metal and gives architectural zinc its characteristic blue-gray appearance. (5.7.5)
6 Finishes
6.1 Prepainted Coil — PVDF and SMP
● AAMA 2605 — 70% PVDF (Kynar 500 / Hylar 5000) — premium architectural
○ AAMA 2604 — 50% PVDF or SMP-PVDF blend — high-performance general
○ AAMA 2603 — commercial polyester — low-exposure or interior only
Per drawings — finish schedule (deferred by default)
6.1.1 Prefinished coil-coated steel and aluminum sheet for architectural sheet metal trim shall be coated with an AAMA 2605, AAMA 2604, or AAMA 2603 system, selected by the Designer of Record based on service life, visual exposure, and budget.
6.1.2 Full-strength 70% PVDF (Kynar 500 / Hylar 5000) systems conforming to AAMA 2605 shall be used for prominent visible exterior architectural metal.
6.1.3 50% PVDF / SMP-PVDF blend systems conforming to AAMA 2604 are appropriate for general commercial trim where the visible exposure is moderate.
6.1.4 Commercial polyester (AAMA 2603) shall not be specified for prominent exterior architectural surfaces with long service-life expectations; it is appropriate only for low-exposure, low-visibility, or interior trim.
6.1.5 The Contractor shall confirm the coil-coating order requirements and lead time at the time of submittal, because a custom color with an 8-week coil lead time can become the critical path of the sheet metal scope.
6.2 Anodized Aluminum — AAMA 611
● AAMA 611 Class I — minimum 0.7 mil coating (exterior architectural)
○ AAMA 611 Class II — minimum 0.4 mil coating (interior or low-exposure exterior)
6.2.1 Anodized aluminum finishes shall conform to AAMA 611, using Class I anodizing (minimum 0.7 mil coating thickness) for exterior architectural use and Class II (minimum 0.4 mil) for interior or low-exposure exterior use only.
6.2.2 The Contractor shall confirm acceptable color variation tolerance with the Designer of Record before ordering, because anodized finishes are inherently variable in color across coils and lots.
6.2.3 The Contractor shall order all anodized aluminum for a single building elevation from a single coil run where uniformity is critical.
6.3 Mill and Natural Finishes
6.3.1 Where mill or natural-finish metal is specified, the Designer of Record shall confirm in writing that the Owner has been informed of the visual progression and that the un-weathered initial appearance is acceptable.
NOTE Once installed, mill-finish metal cannot be made to look like a prepainted finish; substitution after the fact is not feasible. (6.3.2)
6.4 Field Touch-Up
6.4.1 Field touch-up paint shall match the coil-coating system and color exactly and shall be supplied by the same coating manufacturer as the coil.
6.4.2 Touch-up shall be limited to small scratches, cut edges, and fastener heads where the field-applied finish will not be in direct UV exposure (cut edges concealed by the bend, fastener heads beneath a sealant joint).
6.4.3 Field-painted patches on visible surfaces shall be avoided because they weather differently than the surrounding factory finish; pieces with visible damage on prominent surfaces shall be replaced, not touched up.
7 Accessory Materials
7.1 Fasteners
● Stainless steel Type 304, with EPDM-bonded washer
○ Stainless steel Type 316, with EPDM-bonded washer (coastal)
○ Hot-dip galvanized steel (ASTM A153) — interior or concealed only
○ Copper or copper-alloy nails (loose-laid roofing application)
● Stainless steel Type 304 or 316 screws with EPDM-bonded washer
○ Brass screws
● Stainless steel Type 304 (interior, mild exterior)
○ Stainless steel Type 316 (coastal or chloride-exposed)
7.1.1 Fasteners for architectural sheet metal shall be of a metal compatible with the sheet being fastened to avoid galvanic corrosion.
7.1.2 Where compatibility cannot be achieved with a fastener of the same metal as the sheet, the fastener material shall be at least as noble as the sheet metal — never less noble.
7.1.3 Stainless steel screws with EPDM-bonded washers shall be used to fasten prefinished galvanized, Galvalume, aluminum, and stainless sheet to wood blocking, plywood, or steel substrate.
7.1.4 Aluminum fasteners shall be used only with aluminum sheet, and only where the aluminum substrate provides adequate pull-out value.
7.1.5 Copper sheet shall be fastened with copper or stainless steel fasteners, never with galvanized or carbon steel fasteners.
7.1.6 Zinc sheet shall be fastened with stainless steel fasteners.
7.1.7 Exposed fastener heads on visible architectural sheet metal shall be color-matched to the coil finish or covered by a sealant bead and trim.
NOTE Concealed-fastener attachment (cleats, hooks, and clip systems) is the preferred attachment for prominent visible work because it eliminates the maintenance, leak, and aesthetic concerns of an exposed-fastener field. (7.1.8)
7.2 Sealants
7.2.1 Sealants for architectural sheet metal joints shall be selected by the type of joint and the expected movement.
NOTE Three sealant categories are used: (7.2.2)
- Non-curing butyl tape (closed-cell butyl conforming to ASTM D1056) is used as a primary water seal at concealed laps and slip joints where the joint is mechanically clamped but is required to be drainable or movable. Butyl tape is the standard sealant beneath cleats, beneath fasteners through hemmed edges, and at the inside of joint covers in expansion joints.
- Single-component urethane sealant conforming to ASTM C920 Type S, Grade NS, Class 50, Use NT, T, M, A, O is appropriate for sealed joints in metal-to-metal applications where the joint is not the primary water barrier (cap-sealing fastener heads, sealing return legs at terminations). Urethane is paintable and color-matched products are available.
- Single-component silicone sealant conforming to ASTM C920 Type S, Grade NS, Class 50 is appropriate for sealed joints where weathering and movement performance govern and where the joint is not in direct contact with substrates incompatible with silicone (silicone shall not be used where it will be painted in service, or in contact with porous substrates where silicone bleed will stain the substrate). For sealant on PVDF-coated surfaces, the silicone manufacturer shall confirm compatibility and provide adhesion test data; many architectural silicones require a primer on PVDF.
● Urethane — ASTM C920 Type S, Grade NS, Class 50 (paintable; standard for prefinished coil)
○ Silicone — ASTM C920 Type S, Grade NS, Class 50 (highest movement and weathering)
○ Butyl tape — closed-cell, non-curing (concealed laps and slip joints only)
● Yes — sealant manufacturer to confirm adhesion to specified PVDF finish, primer if required
○ Not applicable — sealant not in contact with PVDF surface
7.2.3 Non-curing butyl tape (closed-cell butyl conforming to ASTM D1056) shall be used as a primary water seal at concealed laps and slip joints, beneath cleats, beneath fasteners through hemmed edges, and at the inside of joint covers in expansion joints.
7.2.4 Single-component urethane sealant conforming to ASTM C920 Type S, Grade NS, Class 50, Use NT, T, M, A, O shall be used for sealed metal-to-metal joints that are not the primary water barrier (cap-sealing fastener heads, sealing return legs at terminations).
7.2.5 Single-component silicone sealant conforming to ASTM C920 Type S, Grade NS, Class 50 shall be used for sealed joints where weathering and movement performance govern, except where it will be painted in service or in contact with porous substrates that silicone bleed will stain.
7.2.6 For sealant on PVDF-coated surfaces, the silicone manufacturer shall confirm compatibility and provide adhesion test data, and shall provide a primer where required.
7.3 Underlayment
● Self-adhering polymer-modified bituminous sheet, ASTM D1970, minimum 40 mil
○ High-temperature self-adhering bituminous sheet (where metal is dark and surface temperatures exceed 240°F)
○ Not required — metal overlies membrane base flashing per roofing detail
7.3.1 A self-adhering, polymer-modified bituminous underlayment conforming to ASTM D1970 shall be installed on the substrate beneath all sheet metal flashing surfaces that overlie a structural deck, wall sheathing, or wood blocking.
7.3.2 The underlayment shall be lapped a minimum of 4 inches at side laps and 6 inches at end laps, with all laps rolled.
7.3.3 Where sheet metal is installed over a membrane roof (gravel stops and copings overlapping the membrane base flashing), a separate underlayment beneath the metal is not required, the cleat or hook strip is fastened through the membrane base flashing into structural blocking, and the membrane manufacturer's published detail governs.
7.4 Cleats and Hook Strips
● Continuous cleat — full length of piece (preferred for visible work, simplest ES-1 listing)
○ Intermittent (clip) cleat — confirmed by ES-1 test for as-built spacing
NOTE Cleats and hook strips are continuous or intermittent strips of metal fastened to the substrate that engage a hemmed return on the sheet metal piece, securing it against wind uplift without exposed fasteners through the visible face. (7.4.1)
7.4.2 Cleats shall be of the same metal as the sheet they engage, or a more noble, compatible metal (stainless cleats with stainless or aluminum sheet are common).
7.4.3 Cleat gauge shall be at least equal to the sheet gauge, and typically one gauge heavier where the sheet is at the lighter end of the SMACNA-recommended range.
NOTE Cleat material, gauge, and fastener spacing are integral to the ANSI/SPRI ES-1 wind classification of the assembly. (7.4.4)
7.4.5 Continuous cleats shall be used in preference to intermittent (clip) cleats for prominent visible work, to distribute engagement uniformly along the hem and eliminate localized hem distortion at clip locations.
7.4.6 An intermittent cleat shall not be substituted for a continuous cleat in an ES-1-listed assembly without revised testing; intermittent cleats are acceptable in concealed locations and where the ES-1 test has been performed on the intermittent configuration.
8 Fabrication
8.1 General Principles
8.1.1 Sheet metal shall be brake-formed in the shop wherever practicable, with field forming reserved for closures and end conditions that cannot be pre-dimensioned.
8.1.2 The maximum shipping length of a single piece shall be coordinated with site access and the brake's capability; longer pieces (24 to 30 ft) reduce the number of field joints but require larger trucks, careful handling, and adequate site staging space.
8.1.3 All bends shall be made with the prefinished or painted side outward (where the bend is convex to the finished face) and shall use a brake with sufficient inside-bend radius to avoid cracking the coating.
8.1.4 PVDF-coated coil shall be bent to an inside-bend radius of 1 to 1.5 times the metal thickness or greater without coating fracture; tighter bends require radiused brake dies and a slow press cycle.
8.1.5 Cracked coatings at the apex of a bend are a finish failure that cannot be touched up and shall result in rejection of the piece.
8.1.6 Cut edges shall be deburred and shall not be left sharp or with visible feathers.
8.1.7 Edges that will be exposed in service (the open end of a hem, the lower edge of a gravel stop, the upper edge of an uncapped counterflashing) shall be hemmed back on themselves so that no raw edge is exposed.
8.2 Joints
NOTE Three primary joint types are used in architectural sheet metal: lapped joints sealed with butyl tape or sealant, standing seams (folded and hemmed double-lock seams in long-run pieces), and slip-and-lock joints with backer plates at expansion joints. (8.2.1)
○ Double-lock standing seam — preferred for visible work
● Slip-and-lock with backer plate at expansion joints, double-lock between
○ Lapped with butyl and sealant — short-run or concealed work
8.2.2 The joint type for each piece shall be specified on the shop drawings and shall match the SMACNA detail being followed.
8.2.3 Lapped joints with sealant shall have a minimum lap of 2 inches in the direction of water flow, with a continuous butyl tape concealed within the lap and a continuous bead of sealant tooled to a clean fillet at the upstream edge of the lap.
8.2.4 Standing seams shall be a minimum 1 inch tall, hand-sealed or machine-seamed where the machine is appropriate to the gauge and metal, and double-lock seams shall be used in preference to single-lock for permanent installations.
8.2.5 Slip-and-lock expansion joints (S-locks) shall consist of a backer plate of matching profile lapped into the running joint with butyl tape and a clamping cover or hemmed return that allows the running pieces to slide axially as thermal movement occurs.
8.2.6 The slip-and-lock joint shall be sealed on the upstream side with butyl tape only; sealant shall not bridge the moving portion of the joint, because sealant bridges that constrain movement will be torn open by the first significant thermal cycle.
8.3 Cleats
8.3.1 Cleats shall be fabricated of the same metal type as the sheet they secure, and a gauge equal to or one heavier than the sheet.
8.3.2 Continuous cleats shall be installed in lengths matching the cleated piece, with adjacent cleat sections butted (not lapped) and the joint located so that it does not coincide with a sheet metal joint.
8.3.3 Cleat fastener spacing shall match the ANSI/SPRI ES-1 listing for the assembly, and the listed spacing shall be marked on the shop drawings and verified in the field.
8.3.4 Intermittent cleats, where used, shall be a minimum 2 inches wide and shall be spaced at a maximum of 12 inches on center, or closer per the ES-1 listing.
8.3.5 The intermittent cleat shall be of the same metal as the sheet and shall be set in butyl tape between the cleat and the substrate.
8.4 Hems
● Single hem — 1/2 in fold-back (typical concealed edges)
○ Double hem — folded twice (long-span exposed edges, gutter rim)
○ Open hem with closure — open hem with a separate closure strip
8.4.1 The standard architectural hem shall be a 1/2-inch single hem, formed by bending the sheet 180 degrees back on itself.
8.4.2 Double hems (folded twice) shall be used at long-span edges (gutter outer faces, long fascia bottoms) for additional stiffness.
8.4.3 Drip hems on the lower edges of gravel stops, fasciae, and drip edges shall extend at least 1/2 inch out from the substrate face and shall be turned downward at least 30 degrees from horizontal so that water drips clear of the substrate face rather than wicking back along the metal underside.
8.5 Expansion Joint Provisions
8.5.1 The expansion joint spacing in running sheet metal shall be designed for the metal's coefficient of thermal expansion and the expected temperature range.
NOTE Approximate maximum running lengths between expansion joints, for prefinished coil exposed to direct sun on a low-slope roof in temperate climates, are: (8.5.2)
- Prefinished galvanized or Galvalume steel: approximately 40 ft maximum between expansion joints (coefficient of thermal expansion approximately 7 x 10^-6 in/in/°F)
- Prefinished aluminum: approximately 25 ft maximum between expansion joints (coefficient of thermal expansion approximately 13 x 10^-6 in/in/°F)
- Copper: approximately 30 ft maximum between expansion joints
- Stainless steel: approximately 40 ft maximum between expansion joints
- Zinc: approximately 25 ft maximum between expansion joints
30 ft (conservative; dark colors, high-temperature climates)
40 ft (typical for medium-color prefinished coil in temperate climates)
Per SMACNA Architectural Sheet Metal Manual table for project climate and color
20 ft (dark colors, high-temperature climates)
25 ft (typical for medium-color prefinished aluminum)
Per SMACNA Architectural Sheet Metal Manual table for project climate and color
NOTE Failure to accommodate thermal movement results in buckling in hot weather, joint tearing in cold weather, and fastener pull-through over many thermal cycles. (8.5.3)
NOTE The SMACNA Architectural Sheet Metal Manual provides specific tables keyed to climate zone and surface color, since darker surfaces reach higher peak temperatures and require closer joint spacing. (8.5.4)
8.5.6 Each expansion joint shall be a slip-and-lock joint with backer plate and butyl tape.
8.5.7 Expansion joints shall not be located at corners; corners shall be solidly joined (lapped, soldered, or double-lock-seamed) and the expansion joint shall be located in the running section at least 18 inches from the corner so that the corner does not absorb the entirety of the thermal movement.
8.6 Soldering and Welding
8.6.1 Soldering of copper and lead-coated copper joints shall use lead-free solder per current code requirements, with rosin flux applied, the joint heated to flow temperature with a soldering iron or torch sized for the metal weight, solder drawn into the joint by capillary action, and the joint cleaned of flux residue after cooling.
8.6.2 Soldered joints shall be inspected for full solder penetration, and voids in soldered seams shall be re-soldered.
8.6.3 Soldering of copper greater than 16 oz/sf shall use larger soldering irons (typically electric or fuel-fired) and a slower work pace than 16 oz/sf.
8.6.4 Stainless steel joints in pieces too heavy to solder, or where solder appearance is undesirable, shall be welded by a qualified welder using TIG or MIG welding appropriate to the gauge.
8.6.5 Heat input shall be controlled to minimize distortion and to limit the affected zone where the welded zone may corrode preferentially (sensitization).
8.6.6 Welded stainless joints in visible work shall be ground, polished, and passivated to restore corrosion resistance and a uniform appearance.
8.6.7 Galvanized steel and aluminum joints shall not be soldered or welded; joints in galvanized and aluminum sheet shall be formed by mechanical seams (lapped with sealant, standing seams, slip-and-lock) as described in the Joints section.
9 Roof Edge Securement — ANSI/SPRI ES-1
9.1 Compliance Requirement
30200
45607590105120150200
Default: 75 psf
Per drawings
● ES-1-listed manufactured product — listing meets or exceeds design edge pressure
○ Field-fabricated profile tested per ES-1 for the project as-built configuration
○ Engineered design by licensed engineer demonstrating equivalent wind resistance
NOTE ANSI/SPRI/FM 4435/ES-1 establishes the wind-pressure resistance of metal edge systems used on low-slope roofs and defines three test methods: RE-1 (horizontal displacement after wind pressure), RE-2 (vertical pull-out under wind uplift), and RE-3 (cyclic pressure simulating fluctuating wind). (9.1.1)
9.1.2 IBC Section 1504.5 requires that all metal-edge cover assemblies on low-slope roofs be designed, tested, and labeled in accordance with ES-1 for the wind pressure at the building's perimeter and corner zones, calculated per ASCE 7 components-and-cladding provisions.
NOTE Field-fabricated edge metal (coping, gravel stop, fascia) is not ES-1-listed unless the as-fabricated profile and securement match a tested configuration of the cleat, fastener spacing, hem return, and substrate. (9.1.3)
9.1.4 The Contractor shall not field-fabricate roof-edge metal on a low-slope roof and treat it as code-compliant; either an ES-1-listed manufactured product shall be specified, the field-fabricated profile shall be engineered and tested for the project, or the design shall be by a licensed engineer whose calculation demonstrates compliance with the underlying wind-resistance requirement.
9.2 Cleat and Fastener Pattern
9.2.1 For ES-1-listed edge-metal assemblies, the cleat material, gauge, fastener type, fastener spacing, and substrate are integral to the listing, and substituting any component voids the listing for that section of the roof edge.
9.2.2 The Contractor shall verify in the field that the installed nailer dimensions and the cleat fastener pattern match the ES-1 listing documents in the submittal package; deviation shall be reported to the Designer of Record and corrected before the edge metal is installed.
9.2.3 Continuous wood nailers supporting the cleat and cover shall be pressure-treated for exterior exposure (typically alkaline copper quaternary or copper azole preservative compatible with the cleat and fastener metals), and preservatives that release chloride or that are highly acidic shall be avoided where they contact aluminum or zinc-coated steel.
9.2.4 Nailer attachment to the structure (number, type, spacing of fasteners into the deck or parapet wall) is part of the ES-1-tested assembly and shall not be altered.
10 Counterflashing and Wall Flashing
10.1 Counterflashings at Membrane Roof Base Flashings
○ Reglet — continuous saw-cut groove in concrete or masonry, counterflashing wedged or lead-caulked into reglet
● Manufactured masonry receiver — installed during masonry work, counterflashing engaged at top
○ Below through-wall flashing — counterflashing terminates beneath a separate through-wall flashing
○ Surface-mounted — counterflashing fastened to wall face, top edge sealed (retrofit only)
NOTE Counterflashings protect the top termination of the membrane base flashing from UV, debris, and physical damage; the membrane base flashing remains the primary water barrier, and the counterflashing is a secondary, mechanically removable protection for future re-roofing. (10.1.1)
10.1.2 Counterflashings shall be installed in a reglet in the wall (a continuous saw-cut groove or a manufactured masonry receiver) or under a through-wall flashing in masonry construction.
10.1.3 Surface-mounted counterflashings (fastened to the wall face with exposed fasteners and a top-edge sealant joint) are acceptable only on retrofits where reglet cutting is not feasible, and require periodic sealant replacement because they depend on the sealant joint for water exclusion.
10.1.4 The counterflashing shall lap over the top of the membrane base flashing by a minimum of 4 inches.
10.1.5 The lap zone shall not be sealed (counterflashings are removable for future re-roofing), but the lap geometry shall shed water down the face of the base flashing rather than directing it behind the base flashing.
10.1.6 Counterflashings shall be designed so that any water entering between the counterflashing and the base flashing exits at the bottom of the base flashing onto the roof membrane.
10.2 Through-Wall Flashings at Masonry
10.2.1 Through-wall flashings shall be installed within masonry walls at the base of the wall, at floor lines, at heads and sills of openings, and at shelf angles, to intercept water that has penetrated the outer wythe and direct it back out at the wall face through weep openings.
10.2.2 The exposed drip-edge portion of a through-wall flashing that projects from the wall face shall be sheet metal (typically stainless steel or copper) lapped under or hemmed with the membrane through-wall flashing within the wall.
10.2.3 The through-wall flashing assembly shall be coordinated with the masonry and exterior-wall standards.
10.2.4 The exposed metal drip-edge of a through-wall flashing shall project at least 1/4 inch out from the wall face and shall be hemmed downward at a minimum 30-degree angle so that water drips clear of the wall face.
10.2.5 Where the projection conflicts with the architectural face of the wall, the through-wall flashing shall be flush with the wall face but the membrane portion above shall extend outward to form a drip in front of the wall face, not behind.
10.3 Head and Sill Flashings
○ Prefinished galvanized or Galvalume steel, AAMA 2604 or 2605 coating
● Prefinished aluminum, AAMA 2604 or 2605 coating
○ Stainless steel — Type 304 or 316 (premium and coastal applications)
○ Self-adhering membrane flashing (substitute for sheet metal head and sill flashings on residential or light commercial work)
● Yes — turned-up end tab on each end, minimum 1 in tall, sealed to head flashing back leg
○ No (not acceptable for exterior wall openings)
10.3.1 Head flashings over wall openings (windows, doors, louvers) shall be continuous formed metal pieces that lap over the top of the frame and turn up at the back behind the wall water-resistive barrier (WRB) so that water on the WRB is directed over the head flashing and out beyond the frame.
10.3.2 The head flashing shall extend at least 2 inches beyond each side of the rough opening, with end dams formed on each end (a turned-up tab folded against the back leg) to direct water out the front of the flashing rather than over the side.
10.3.3 Sill (pan) flashings below window openings shall be continuous below the window rough sill, lapped over the WRB below and turned up at the front and each side to form a pan that contains any water entering the rough opening and directs it back outward beneath the window.
10.3.4 Pan flashings shall be installed before the window unit is set; pan flashings retrofitted after the window is set are not effective.
11 Gutters and Downspouts
11.1 Gutter Design Basis
○ Prefinished galvanized or Galvalume steel, AAMA 2604 or 2605 coating, minimum 24 ga
● Prefinished aluminum, AAMA 2604 or 2605 coating, minimum 0.050 in (18 ga equivalent)
○ Copper, ASTM B370, minimum 20 oz/sf
○ Stainless steel, Type 304 or 316, minimum 24 ga
○ 1/16 in per ft (minimum)
● 1/8 in per ft (preferred)
○ 1/4 in per ft (short runs only; visible slope on long runs)
Per drawings — civil and roof drawings (deferred by default)
11.1.1 Gutter sizing (cross-sectional area, front and back heights, downspout outlet size and spacing) is the responsibility of the Designer of Record, established by a roof drainage calculation based on the contributory roof area, the design rainfall intensity (typically the 100-year, 5-minute storm for primary drainage per IBC Section 1611 or local code), and the gutter slope.
11.1.2 The gutter cross-section shall be confirmed against the calculated flow before fabrication.
11.1.3 The gutter shall be sloped to downspout outlets at a minimum of 1/16 inch per foot, with 1/8 inch per foot preferred where the gutter length and parapet height allow.
11.1.4 Level gutters shall not be specified, because they do not drain reliably (small construction tolerances result in localized low spots and ponding).
11.2 Gutter Joinery
11.2.1 Gutter joints shall be soldered (copper, lead-coated copper, terne-coated stainless) or formed with a slip-and-lock backer-plate expansion joint (aluminum, steel, Galvalume, stainless) at intervals not exceeding the metal's maximum running length between expansion joints.
11.2.2 Aluminum and steel gutters that cannot be soldered shall be detailed to depend on butyl tape and sealant at lapped joints.
11.2.3 Lapped-and-sealed gutter joints shall be in the direction of flow (upstream piece outside, downstream piece inside), a minimum 1 inch lap, with butyl tape concealed within the lap and a tooled sealant bead at the upstream edge.
11.2.4 End caps on gutters shall be of the same metal, formed to match the gutter profile, and joined with the gutter by soldering (copper, stainless) or by a sealed lap (aluminum, steel).
11.3 Gutter Hangers and Brackets
24 in o.c. (copper and high-snow-load applications)
32 in o.c. (typical aluminum and steel)
36 in o.c. (light gauge gutters in low-snow climates)
11.3.1 Gutters shall be supported by hangers or brackets at maximum 32-inch spacing for steel and aluminum and at 24-inch spacing for copper (which is heavier and softer).
11.3.2 Hangers shall be of a metal compatible with the gutter; stainless hangers are universal.
11.3.3 Hangers shall be designed to support the weight of the gutter filled with water plus a snow and ice load where applicable, because ice-loaded gutters in cold climates can weigh several times the empty gutter weight.
11.3.4 Hangers shall not penetrate the inside or bottom of the gutter (puncturing the water-bearing pan); hangers shall be of a type that engages the outer rim of the gutter from above (hidden hangers, strap hangers over the gutter outer rim) so that water in the gutter does not encounter a fastener penetration.
11.4 Downspouts and Conductor Heads
○ 3 in x 4 in rectangular (typical commercial)
○ 4 in x 5 in rectangular (larger contributory area)
○ 4 in diameter round
○ 5 in diameter round
○ 6 in diameter round (large contributory area or industrial)
● Per Designer of Record roof drainage calculation
Per drawings
6 ft o.c.
10 ft o.c.
12 ft o.c.
11.4.1 Downspouts shall be sized per the roof drainage calculation and shall be a minimum 3 inches by 4 inches (rectangular) or 4-inch diameter (round) on commercial buildings.
11.4.2 Downspout joints shall be lapped in the direction of flow (upper piece outside, lower piece inside) by a minimum of 1 inch, and shall be sealed only at the upper edge of the lap with sealant or soldered.
11.4.3 Downspouts shall be anchored to the wall at maximum 10-ft spacing using straps of the same metal as the downspout.
11.4.4 Downspouts shall discharge to a tied-in storm-drain inlet, a splash block, or a daylight outlet, whichever is specified on the civil drawings, and shall not discharge to a horizontal grade-level surface without a splash block or routing.
11.4.5 Downspout discharge shall be coordinated with Below Grade Waterproofing foundation drainage at any below-grade outlet condition. 11.4.6 Conductor heads (collection boxes set at the top of a downspout to receive water from a scupper or short transition piece) shall be sized to hold the design flow without overflow, formed of the same metal as the downspout, and provided with an overflow lip on the open face that directs overflow water outward rather than back against the wall.
12 Coping
12.1 Function and Design Basis
● Prefinished aluminum, minimum 0.050 in (18 ga equivalent), AAMA 2605 PVDF
○ Prefinished galvanized or Galvalume steel, minimum 24 ga (G90 / AZ50), AAMA 2605 PVDF
○ Stainless steel, Type 304 or 316, minimum 24 ga (coastal and corrosive environments)
○ Copper, minimum 20 oz/sf (historic and premium projects)
○ Zinc, minimum 0.8 mm (premium projects)
● 1/4 in per ft to inside (toward roof) — preferred
○ 1/4 in per ft to outside (away from building) — only where roof side is unprotected
○ Bidirectional (peaked center) — not preferred; creates two drip lines, two edge issues
NOTE Coping caps the top of a parapet wall, protecting both the wall construction and the inside-face membrane base-flashing termination from water infiltration from above. (12.1.1)
12.1.2 Coping is a roof-edge component subject to ANSI/SPRI ES-1; copings shall be ES-1-listed (or engineered-equivalent) for the design wind pressure at the parapet edge zone, which is consistently higher than the field-zone pressure.
12.1.3 The coping cap shall be wider than the parapet wall by enough on each side to provide a drip edge clear of the parapet face — typically a minimum 1-1/2 inch overhang on the outside face and 1 inch on the inside face, with both edges hemmed and turned downward to drip away from the parapet face.
12.1.5 The slope direction shall be toward the roof side so that water leaving the coping falls onto the membrane rather than onto the wall face, which over time accumulates staining and increases wall water-intrusion risk.
12.2 Coping Joinery and Expansion
● Double-lock standing seam (preferred for visible work)
○ Lapped with butyl tape and sealant (downstream lap inside)
12.2.1 Coping shall be jointed at maximum spacing per the metal's expansion-joint table (typically 40 ft for steel/Galvalume and stainless, 25 ft for aluminum, 30 ft for copper) using slip-and-lock backer-plate joints with butyl tape.
12.2.2 Between expansion joints, coping pieces shall be joined by double-lock standing seams or by lapped-and-sealed joints, with lapped joints in the direction of slope so that water sheds over the joint, not under.
12.2.3 Corners shall be solidly joined with mitered or soldered corners; expansion joints shall not be located at corners.
12.2.4 The cleat or continuous hook strip that engages the coping cap shall be ES-1-listed with the coping cap as an assembly.
12.2.5 The cleat shall be fastened to the parapet top through a continuous pressure-treated wood nailer at the spacing required by the ES-1 listing.
12.2.6 Coping cleats shall be fastened through butyl tape to seal the fastener penetrations against water infiltration past the cleat.
13 Wall Expansion Joints and Expansion Joint Covers
NOTE Building expansion joints — joints that allow the structural framing on either side to move independently — penetrate the building envelope at the wall and roof. (13.1)
● Proprietary engineered expansion-joint cover assembly (preformed bellows + metal trim)
○ Site-fabricated sheet metal cover with elastomeric bellows beneath
○ Composite metal-and-membrane expansion-joint cover
Per drawings
Per drawings — structural drawings (deferred by default)
13.2 The exterior face of the wall expansion joint shall be covered by a flexible expansion-joint cover that accommodates the design movement (typically plus-or-minus 25 to 50 percent of the joint width) and seals the joint against weather.
13.3 The sheet metal trim portion of the expansion-joint cover shall be of the metal type matching adjacent flashing and shall be lapped or sealed to the adjacent flashing or wall membrane so that water at the wall membrane plane is directed past the expansion joint without entering it.
13.4 At the wall-to-roof transition, the expansion-joint cover shall transition continuously from the wall plane onto the roof plane without interruption, because a discontinuous expansion-joint cover at the wall-roof transition is a common leak source.
14.1 Galvanic Compatibility
● EPDM gasket — minimum 1/16 in thick, full-coverage between dissimilar metals
○ Butyl tape — non-curing closed-cell, full-coverage
○ Polyethylene sheet — minimum 6 mil, full-coverage
○ Bituminous paint coat on more noble metal at contact
○ Not applicable — no dissimilar metal contact in this scope
14.1.1 Galvanic isolation shall be provided wherever metals at significantly different points in the galvanic series are in direct contact, in water-coupled proximity (water from one metal running onto another), or in shared-fastener contact.
14.1.2 Isolation shall be achieved by separating the metals with a polymer barrier (EPDM gasket, butyl tape, polyethylene sheet), by coating the more noble metal with a barrier coat where it contacts the less noble, or by using a fastener at least as noble as the more noble metal.
NOTE In the architectural galvanic series — from most anodic (sacrificed first) to most cathodic (protected): zinc, aluminum, galvanized steel, mild steel, copper alloys, stainless steel — aluminum, zinc, and galvanized steel are most commonly corroded, and copper and stainless most commonly drive corrosion of others. (14.1.3)
14.2.1 Copper sheet shall not be installed above unprotected aluminum, galvanized steel, or zinc, including via water runoff that washes copper salts onto the metal below.
14.2.2 Where copper is installed above metal of a lower nobility, the metal below shall be protected by a non-reactive barrier (for example, a continuous EPDM sheet between the copper and the metal below).
14.2.3 Lead-coated copper, terne-coated stainless, and other historic combinations shall have their specific compatibility requirements confirmed with the metal manufacturers before specification.
14.2.4 Aluminum sheet shall not be in direct contact with fresh mortar, fresh concrete, or pressure-treated lumber containing copper-based preservatives (alkaline copper quaternary, copper azole) without a barrier coat or polymer separation.
14.2.5 Isolation between an aluminum cleat and an ACQ-treated wood nailer is required, because ACQ lumber is acidic and contains soluble copper, both of which attack aluminum.
14.2.6 Galvanized steel and zinc sheet shall not be in direct contact with fresh mortar or concrete or in direct copper contact, by which they are degraded.
14.2.7 Stainless fasteners through aluminum, galvanized, or zinc sheet shall use EPDM washers to seal the fastener penetration and reduce moisture coupling, even though the small fastener-to-sheet area ratio generally limits corrosion to acceptable levels.
15 Installation Sequence
15.1 Coordination with the Roofing Trade
NOTE The sheet metal scope is interleaved with the roofing scope at every roof-to-wall, roof-to-curb, and roof-edge interface. (15.1.1)
15.1.2 The sequencing of which trade installs which component first is fixed by the function of each piece and shall not be altered:
- Wood nailers and blocking at the roof edge and on top of parapets shall be in place before the roofing membrane is installed. The roofing Contractor uses these nailers to terminate the membrane field and base flashings, and the sheet metal Contractor uses them to anchor cleats and edge metal.
- The roofing Contractor installs the membrane field, the membrane base flashings up the parapet inside face, and any membrane-bonded edge components that are integral to the roofing manufacturer's warranty. Where the edge-metal assembly is supplied as part of the roofing manufacturer's warranted package, the roofing Contractor installs that edge metal.
- After the membrane base flashings are complete and probed, the sheet metal Contractor installs counterflashings over the top of the base flashings, copings on top of the parapet, and gravel stops or fascias at unparapeted edges.
- Wall flashings, gutters, downspouts, and trim are installed in coordination with the wall-cladding and rough-carpentry trades, sequenced so that flashings are in place before the wall cladding laps over them.
15.1.3 The sequencing of which trade installs which component first is fixed by the function of each piece and shall not be altered from the order listed above.
15.1.4 The pre-installation conference shall finalize the sequencing for the specific project, with attention to areas where the typical sequence may be altered (for example, where a coping is integrated with a unitized rainscreen panel system and installed as part of the panel scope rather than the sheet metal scope).
15.2 Substrate Acceptance
15.2.1 The sheet metal installer shall inspect all substrates before installation and shall not proceed until wood nailers are properly fastened, of the specified thickness and treatment, at the correct elevation and width; membrane base flashings are fully bonded and probed where they will be lapped by counterflashings or copings; masonry is at the correct dimension with clean reglet cuts to the specified depth; and structural framing supporting heavy pieces (gutters, conductor heads) is in place at the correct elevation.
15.2.2 Deficient substrates shall be reported to the General Contractor in writing, and the sheet metal Contractor shall not proceed over a non-conforming substrate without correction.
15.3 Field Cutting and Fitting
15.3.1 Where field cutting is unavoidable (at end conditions, around penetrations, at irregular corners), cuts shall be made with snips, hand shears, or a powered nibbler appropriate to the metal.
15.3.2 Abrasive cutting wheels and grinders shall not be used on prefinished coil-coated sheet, because the heat and abrasive damage the coating along the cut edge and produce a non-touchable edge condition; powered shears or nibblers that do not heat the metal are required.
15.3.3 Cut edges shall be deburred and shall receive touch-up paint per the Field Touch-Up section.
16 Finishes and Touch-Up
16.1 Storage and Handling
16.1.1 Prefinished coil and panel shall be stored on edge, off the ground, under protective wrap or cover, in a dry location, because coil-coated panels stored flat with weight on top develop oil-canning, dimpling, and finish damage along the contact lines.
16.1.2 Panels and pieces shall be protected from moisture during storage, because water trapped between panels causes white-rust on Galvalume and aluminum and surface staining on prefinished coil that may not be removable.
16.1.3 Protective films applied at the coil-coating mill shall be left in place during fabrication and installation, and shall be removed only at substantial completion and before any UV exposure that would bond the film to the finish (typical maximum film exposure time is 90 days; the Contractor shall confirm with the coil manufacturer).
16.2 Cleaning
16.2.1 Installed sheet metal shall be cleaned at substantial completion of all installation debris, sealant smears, mortar residue, and protective film.
16.2.2 Cleaning shall use water and a mild detergent (pH between 5 and 9), applied with a soft cloth or sponge and rinsed clean with potable water.
16.2.3 Solvents, acid cleaners, abrasive cleaners, and steel-wool or scratch-pad scrubbers shall not be used on prefinished coil, because these damage the finish.
16.2.4 Mortar smears shall be removed promptly (within minutes of contact, before the mortar cures) with water; cured mortar shall be removed by mechanical scraping with a soft plastic or wood scraper, never by acid wash.
16.3 Touch-Up
16.3.1 Touch-up paint matching the coil finish shall be applied to all field-cut edges, exposed fastener heads, and minor scratches not exceeding 1/4 inch in any dimension.
16.3.2 Larger scratches, dents, or finish damage shall not be touched up on visible surfaces; pieces with significant damage shall be replaced.
16.3.3 Touch-up paint shall be allowed to dry per the manufacturer's instructions before the area is subject to water contact or further work.
17 Cleaning and Acceptance
17.1 The sheet metal installation shall be jointly inspected at substantial completion by the Contractor, the Designer of Record, and the Owner's representative.
17.2 The inspection shall verify that all pieces are in their final position; that joints are properly formed and sealed; that all expansion joints are functional (no sealant bridges across moving portions); that ES-1-listed roof-edge metal is installed per the listed assembly with the correct cleat, fastener type, and spacing; that all flashings overlap correctly and shed water in the design direction; that gutters are sloped and unobstructed; that downspouts are anchored and discharge correctly; that dissimilar-metal isolation is in place where required; and that finished surfaces are clean and free of damage.
17.3 Deficiencies identified at substantial completion shall be corrected before the Contractor's warranty period begins.
18 Warranty
18.1 Fabricator and Installer Warranty
18.1.1 The Contractor shall provide a written workmanship warranty for the installed sheet metal for a minimum of two years from the date of substantial completion.
18.1.2 The warranty shall cover defects in fabrication, joinery, and installation, including leaks at sheet metal joints and detachment under design wind loads.
18.1.3 The Contractor's warranty is in addition to the finish manufacturer's warranty and does not substitute for it.
18.2 Finish Manufacturer Warranty
20 years (AAMA 2604 finishes)
30 years (AAMA 2605 PVDF finishes)
40 years (premium PVDF systems)
18.2.1 The prefinished coil manufacturer shall provide a written warranty against finish film integrity, color fade, and chalk per the AAMA 2605 or 2604 schedule for the specified finish.
NOTE Typical PVDF (AAMA 2605) warranties are 30 years against film failure, 30 years against chalk (with a quantitative limit on chalk rating), and 30 years against color fade (with a quantitative limit on delta-E change); 50% PVDF / SMP (AAMA 2604) warranties are typically 20 years for similar metrics. (18.2.2)
18.2.3 Project conditions that match any finish-warranty exclusion (heavy industrial fallout, marine spray within 1,500 ft of salt water, agricultural ammonia exposure, chemical exposure, physical impact, or substrates outside the manufacturer's approved substrate list) shall be identified before submittal so that the finish system can be confirmed appropriate for the exposure.
18.2.4 The Contractor shall submit the finish manufacturer's warranty form with the submittals.
18.3 Roof-Edge Assembly Warranty
18.3.2 Where the roof-edge metal is supplied by an independent edge-metal manufacturer with its own warranty, the Contractor shall obtain that warranty separately and submit it at closeout.
18.3.3 Coordination between the membrane warranty and the edge-metal warranty shall be confirmed before the edge-metal product is selected, because an edge-metal product not on the membrane manufacturer's approved-products list can void the membrane warranty at the perimeter.
19 Common Errors and RFI Generators
NOTE Architectural sheet metal generates a consistent set of field errors and RFIs. (19.1)
NOTE The following are among the most frequently encountered. (19.2)
19.3 Field-fabricated coping or gravel stop on a low-slope roof: the Contractor shall not field-fabricate roof-edge metal on a low-slope roof, because such metal without an ES-1 listing for the as-built profile is not IBC-compliant; an ES-1-listed manufactured product or engineered profile is required.
19.4 Sealant bridging across expansion joints: expansion joints shall be sealed only on the upstream side with butyl tape, and the moving portion of the joint shall not be sealed, because a sealant bridge constrains thermal movement and will be torn open at the first significant temperature swing.
19.5 Termination bar on a horizontal surface: the counterflashing scope shall not include a termination bar on a horizontal surface (such as flat on a parapet top); counterflashings shall be vertical and terminate into a reglet or under a through-wall flashing.
19.6 Drip edge insufficient projection: drip edges on copings, fasciae, and through-wall flashings shall project at least 1/2 inch and be turned downward at least 30 degrees from horizontal, or they conduct water back along the underside to the substrate.
19.7 Missing head flashing end dams: every head flashing shall have an end dam on each end, formed and sealed at the flashing's back leg, or water runs off the side of the flashing into the wall cavity.
19.8 Galvanized fasteners in copper or stainless sheet: fastener material shall always be at least as noble as the sheet, never less noble, because a galvanized fastener in copper or stainless forms an aggressive galvanic couple that fails the fastener head within years and tracks rust staining down the metal face.
19.9 ACQ-treated nailer in contact with aluminum coping cleat: the aluminum-ACQ contact shall be isolated with a polymer barrier, or a non-ACQ preservative shall be specified for the nailer, because aluminum cleats on ACQ lumber corrode at the contact face within months in wet exposures.
19.10 Solder flux not cleaned after copper soldering: all flux residue shall be neutralized and washed off after the joint cools, because rosin flux residue absorbs moisture and accelerates corrosion under the solder line, eventually breaking the solder bond.
19.11 Coping pieces installed without a slope: coping shall be installed with a minimum 1/4 inch per foot transverse slope, typically toward the roof side, because level coping caps retain water that accelerates finish degradation and water entry at joints and fasteners.
19.12 Gutter or downspout undersized for the contributory area: sizing shall be confirmed against the SMACNA tables or a roof drainage calculation before fabrication, because undersized gutters overflow during design storms and route water onto the wall below and the foundation.
19.13 Mortar smears on prefinished coil left to cure: mortar smears shall be removed with water within minutes of contact, not at end of day, because mortar on prefinished aluminum or Galvalume bleaches the finish and produces a permanent visual mark even after removal.
19.14 Copper runoff onto aluminum, zinc, or galvanized below: the metal below shall be protected by a continuous barrier, or the system layout shall be revised so that copper drainage does not pass over a less noble metal, because copper salts washing onto the metal below drive galvanic corrosion.
19.15 Coil-coated panels stored flat with weight on top: panels shall be stored on edge or otherwise unloaded during storage, because stacking pressure causes oil-canning, finish indentation, and edge damage along contact lines.
19.16 Coping cleat fastener pattern not matching ES-1 listing: the Contractor shall verify the as-installed cleat fastener pattern against the listing documentation in the submittal before closing in the work, because substituting fastener type, spacing, or substrate from the ES-1-listed assembly voids the listing.