Wall flashings are among the most consequential — and most litigated — components of a building envelope specification. Head flashings above window openings, through-wall sill flashings at masonry bases, and jamb conditions at CMU reveals generate more water infiltration callbacks than almost any other Division 07 element. A tight, technically accurate specification prevents the improvised field solutions that become the source of those callbacks.
CSI MasterFormat Sections for Wall Flashing
Wall flashing work is split across two primary MasterFormat sections, depending on material type:
| Section | Title | Covers |
|---|---|---|
| 07 62 00 | Sheet Metal Flashing and Trim | Metal head flashings, through-wall flashings, sill pans, counter flashings, drip edges |
| 07 65 00 | Flexible Flashing | Self-adhering membrane sill pans, jamb wraps, through-wall membrane flashings |
| 07 27 00 | Air Barriers | Integrated air/water barrier systems that function as flashing at openings |
| 07 60 00 | Flashing and Sheet Metal | Parent section; may be cited by reference only |
Most commercial and institutional projects specify both 07 62 00 and 07 65 00: metal for head and sill conditions at CMU, membrane for jamb wraps and sill pans at framed openings. The interface between metal and membrane work must be explicitly detailed in the spec — gaps here are where field improvisation, and leaks, originate.
Head Flashing Above Window Openings
Metal head flashing above window and door openings intercepts water that migrates through the outer masonry wythe or cladding and directs it to the exterior. A properly specified head flashing has four functional elements: a back leg (turns up against the structure), a sloped bed, a drip edge at the face, and an end dam at each jamb.
Minimum Dimension Requirements
SMACNA Architectural Sheet Metal Manual, 7th Edition, provides dimension minimums for head flashings. The following represent standard practice for CMU and brick veneer conditions:
| Element | Minimum Dimension | Notes |
|---|---|---|
| Back leg height | 4 inches | Must extend above highest anticipated water level |
| Bed slope | 1/8" per foot minimum | Slope toward exterior to promote drainage |
| Drip edge projection | 3/4 inch beyond face | Required to ensure water clears the wall face |
| End dam height | 1 inch minimum | 1.5–2" in high-exposure or coastal conditions |
| Bearing on lintel | 4 inches minimum | Flashing must have full bearing on the structural support |
Material Specification for Head Flashings
A. Steel: 24 gauge (0.0239 inch) minimum, ASTM A653 Grade 33 galvanized, G90 coating minimum; or Galvalume (ASTM A792) where exposed to view.
B. Aluminum: .040 inch (1.0 mm) minimum, ASTM B209, Alloy 3003-H14 or 3105-H14.
C. Kynar 500 Finish: Where head flashings are exposed at building face — PVDF coil coating per AAMA 2605, minimum 70% PVDF resin, color as selected by Architect.
D. Stainless Steel: Type 304, 26 gauge minimum, where specified for corrosive environments or high-humidity exposures.
Through-Wall Flashing in CMU Construction
Through-wall flashings in concrete masonry unit (CMU) walls intercept water that infiltrates through the wall assembly and direct it to weep holes at the exterior face. They are required by IBC at the base of walls, at floor lines, over openings, and at any horizontal interruption of the drainage plane.
Placement Requirements
IBC Section 1404 and SMACNA both require through-wall flashing at:
- The base of exterior walls, above grade, sloped away from the building
- Above the top of every window and door opening (head flashing)
- At shelf angles, structural ledges, and horizontal projections
- Where the wall meets any horizontal surface (roofs, terraces, balconies)
- At the top of parapet walls, integrated with coping cap anchorage
Weep Hole Specification
Through-wall flashings must be accompanied by weep holes to allow the water collected by the flashing to escape. Weep holes in mortar joints must be specified in both the masonry section and the flashing section to avoid conflicts:
A. Provide open-joint weep holes at maximum 24 inches on center at the course immediately above all through-wall flashings.
B. Weep holes shall be formed by omitting mortar in head joints of the outer wythe at designated locations.
C. Weep hole inserts: Plastic cell weeps or cotton rope wicking are acceptable alternatives at 16 inches on center.
Coordination note: Through-wall flashing installation must be sequenced before the outer wythe masonry is laid. Specify in Division 07 62 00 that the flashing contractor shall coordinate with the masonry contractor (Division 04 20 00) for installation sequence. Flashing installed after masonry is in place cannot be properly lapped and is a common source of leaks.
Sill Pan Flashings at Window Openings
Sill pan flashings prevent water that infiltrates at the window sill from entering the wall assembly. In masonry construction, they are often metal; in wood-framed construction, self-adhering membrane is typically preferred. The sill pan must be a fully water-managed assembly — not simply a slope or a sealant joint.
Sill Pan Design Requirements
A properly designed sill pan consists of:
- Back leg: Turns up a minimum 2 inches against the rough opening header or sub-sill framing
- Side legs (end dams): Turn up a minimum 1 inch at each jamb, formed as part of the pan or field-soldered/sealed
- Sloped bed: Minimum 1/8" per foot slope toward the exterior
- Front lip or drip: Extends past the exterior face with a drip detail to direct water away from the wall
Jamb Flashing Coordination
Jamb conditions at masonry walls require coordination between the window installer and the flashing installer. The spec should address:
- Whether jamb flashing is metal or membrane, and by which trade
- How the jamb flashing integrates with the head flashing end dam
- Sealant joint location and responsibility (window installer vs. flashing installer)
- Whether a jamb receiver or casing bead is required at the masonry reveal
Specification Language for Division 07 62 00 Wall Flashings
The following is representative Part 3 execution language for through-wall metal flashings in CMU construction:
A. General: Install flashings in accordance with SMACNA Architectural Sheet Metal Manual, 7th Edition, Chapter 3 details.
B. Lap end joints a minimum of 6 inches; seal laps with compatible sealant and mechanically fasten at 12 inches on center.
C. Seal all penetrations through flashings (ties, anchors, conduit) with compatible sealant applied in two passes.
D. Turn back legs up a minimum of 4 inches against structure or backup wall.
E. Set flashing level or with positive slope toward exterior as indicated.
F. Where flashing terminates at end dams, form end dam by turning up minimum 1 inch; solder or seal to flashing body.
G. Do not allow mortar to block weep holes during masonry installation; protect weep holes during construction.
Common Specification Failures at Wall Flashings
These are the most frequent deficiencies in Division 07 62 00 wall flashing specifications:
- No end dam requirement: Head flashings specified without requiring end dams allow water to run off the ends of the flashing and into the wall cavity.
- Insufficient lap requirements: Lap joints at less than 4 inches in field-soldered metal work frequently fail over time. Six-inch laps are standard practice.
- Missing sealant compatibility requirement: Certain sealants attack Galvalume or aluminum. The spec must require compatibility verification.
- No installation sequence language: Without explicit sequencing requirements, flashing is often installed after masonry, which prevents proper integration with the drainage plane.
- Gauge inconsistency between sections: When the Division 07 spec and the Division 08 window spec each call out different sill pan materials or gauges, field confusion and substitutions follow.
Submittal Requirements for Wall Flashings
Division 07 62 00 wall flashing submittals should include:
- Shop drawings showing each flashing type (head, sill, jamb, through-wall base) with full leg dimensions and material call-out
- Material certifications confirming ASTM compliance for steel (ASTM A653 or A792) or aluminum (ASTM B209)
- PVDF coating certification if Kynar-finished flashings are specified
- Sealant product data and compatibility documentation
- Installer qualifications if specified
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Frequently Asked Questions
What CSI MasterFormat section covers wall flashing?
Wall flashing is covered under Division 07 62 00 (Sheet Metal Flashing and Trim) for field-fabricated through-wall and sill flashings, and Division 07 65 00 (Flexible Flashing) for membrane-based flashings at window openings. Many projects include both sections: 07 62 00 governs metal head and sill flashings, while 07 65 00 covers self-adhering membrane sill pans and jamb wraps.
What is the minimum gauge for through-wall metal flashing on a CMU building?
SMACNA Architectural Sheet Metal Manual specifies minimum 26 gauge (0.0179 inch) steel for concealed through-wall flashings and minimum 24 gauge (0.0239 inch) for exposed metal head flashings above window openings. For aluminum, the minimum is .032 inch (0.8 mm) for concealed applications and .040 inch (1.0 mm) for exposed applications. Thicker gauges are appropriate when spans exceed 4 feet between supports.
What is the required end dam height for sill flashings?
SMACNA recommends end dams with a minimum 1-inch upturned leg at each jamb condition for sill flashings. In high-exposure or coastal environments, 1.5 to 2 inches is more common practice. The end dam must be soldered or sealed to the sill pan body to prevent water from bypassing the dam at the corner — a failure mode that frequently causes interior water damage.
Should head flashing above a window be specified in 07 62 00 or 08 00 00?
Metal head flashing above window openings is typically specified in Division 07 62 00 (Sheet Metal Flashing and Trim), not in Division 08 (Openings). This is consistent with CSI MasterFormat organization, which places flashing and moisture control in Division 07 regardless of proximity to the window opening. The window installer and flashing installer must coordinate, and the spec should explicitly assign installation sequence responsibility.
Do through-wall flashings require weep holes?
Yes. Through-wall flashings in masonry (CMU or brick) must include weep holes at the outer wythe to allow drainage of water intercepted by the flashing. Weep holes are typically spaced at 24 inches on center for open-joint weeps, or at every mortar joint with a wicking material. The spec should designate both the weep hole spacing and the weep hole type (open joint, cotton wicking, or plastic cell weep).