Sheet Metal Flashing and Trim
Corpus sync: neutrality remakes, note hygiene, datasheet relocation, transformer-split cross-refs
Showing changes from Rev 5
to Rev 6
in Sheet Metal Flashing and Trim.
---
title: Sheet Metal Flashing and Trim
…95 unchanged lines
- "Sealant compatibility certifications (including PVDF pre-treatment requirements)"
- "Cut list and yield plan for copper, zinc, and stainless steel scopes"
−default: [Product data sheets for each metal type (ASTM spec, gauge, coating, alloy/temper, finish), 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), Fabricator qualifications with project references for metal type and joint methods]
+default:
+ - "Product data sheets for each metal type (ASTM spec, gauge, coating, alloy/temper, finish)"
+ - "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)"
+ - "Fabricator qualifications with project references for metal type and joint methods"
```
…30 unchanged lines
- "Final marked-up shop drawings (as-installed expansion joints, field-cut pieces, field repairs)"
- "Maintenance instructions for cleaning, inspection, and sealant joint maintenance"
−default: [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]
+default:
+ - "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"
```
…33 unchanged lines
### 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. {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. {note}
+### The Designer of Record shall establish the metal type for each piece in the scope.
+
```datasheet
label: Predominant Sheet Metal Type
…9 unchanged lines
default: "Prefinished galvanized steel — ASTM A653, G90 coating designation"
```
−
−### 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. {note}
−### The Designer of Record shall establish the metal type for each piece in the scope.
### 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.
…263 unchanged lines
### Sealants for architectural sheet metal joints shall be selected by the type of joint and the expected movement.
−### Three sealant categories are used: {note}
−- **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.
−
```datasheet
label: Primary Sealant at Sealed Sheet Metal Joints (head and sill flashings, lap joints, terminations)
…5 unchanged lines
default: "Urethane — ASTM C920 Type S, Grade NS, Class 50 (paintable; standard for prefinished coil)"
```
+### Three sealant categories are used: {note}
+- **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.
+
+### 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.
+### 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).
+### 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.
+### For sealant on PVDF-coated surfaces, the silicone manufacturer shall confirm compatibility and provide adhesion test data, and shall provide a primer where required.
+
```datasheet
label: Sealant Compatibility with PVDF Finish Required (submit adhesion test data)
…5 unchanged lines
```
−### 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.
−### 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).
−### 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.
−### For sealant on PVDF-coated surfaces, the silicone manufacturer shall confirm compatibility and provide adhesion test data, and shall provide a primer where required.
−
## Underlayment {toc}
…46 unchanged lines
### 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. {note}
+### The joint type for each piece shall be specified on the shop drawings and shall match the SMACNA detail being followed.
+
```datasheet
label: Coping and Fascia Field Joinery
…5 unchanged lines
default: "Slip-and-lock with backer plate at expansion joints, double-lock between"
```
−
−### The joint type for each piece shall be specified on the shop drawings and shall match the SMACNA detail being followed.
### 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.
### 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.
…28 unchanged lines
### The expansion joint spacing in running sheet metal shall be designed for the metal's coefficient of thermal expansion and the expected temperature range.
−### Approximate maximum running lengths between expansion joints, for prefinished coil exposed to direct sun on a low-slope roof in temperate climates, are: {note}
−- 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
−
```datasheet
label: Maximum Spacing Between Expansion Joints — Prefinished Steel and Galvalume
…17 unchanged lines
default: "Per SMACNA Architectural Sheet Metal Manual table for project climate and color"
```
+### Approximate maximum running lengths between expansion joints, for prefinished coil exposed to direct sun on a low-slope roof in temperate climates, are: {note}
+- 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
+
### Failure to accommodate thermal movement results in buckling in hot weather, joint tearing in cold weather, and fastener pull-through over many thermal cycles. {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. {note}
…24 unchanged lines
min: 30
max: 200
− setpoints: [45, 60, 75, 90, 105, 120, 150, 200]
+ setpoints: [30, 45, 60, 75, 90, 105, 120, 150, 200]
default: 75
```
…242 unchanged lines
## Building expansion joints — joints that allow the structural framing on either side to move independently — penetrate the building envelope at the wall and roof. {note}
+## 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.
+
```datasheet
label: Wall Expansion Joint Cover Type
…13 unchanged lines
default: deferred
```
−
−## 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.
## 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.
## 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.
…144 unchanged lines
## 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.
## 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.