Flash Exterior Wall Penetrations

A. Finished-Project Specification

Scope: flashing of every scheduled representative penetration on the assigned elevation — at minimum, one hose bibb, one pipe or duct, one round vent, one electrical box, and one cable or conduit penetration — completed to the point of readiness for the vent, utility block, or cover installed in Project 17.

B. Required Documentation Schedule

Document	Source	Confirmation Required
Penetration schedule	Design professional / plan set	Type, location, size, and clearance confirmed for each penetration
WRB and flashing product instructions	Manufacturer	Compatible products, primer, and application conditions confirmed
Mounting-block details	Design professional / manufacturer	Backing size, fastening, and support confirmed for each block
Prior rainscreen and WRB inspection records	Project 3 and Project 10 records	Confirmed complete and undamaged before penetration work begins
Trade coordination record	General contractor / other trades	De-energized, disconnected, or depressurized status confirmed where applicable

C. Preparation Materials and Consumables

• Flashing membrane: approved self-adhered flashing sized to each sill, side, and head layer, matching the WRB and product instructions.
• Round-penetration accessories: boots, gaskets, split collars, or liquid flashing sized to each round penetration's diameter.
• Mounting blocks and backing: approved structural backing components matching the fixture or cover schedule.
• Sealant: compatible sealant limited to the designated annular gap or joint for each penetration type.
• Documentation: one penetration-flashing record per elevation, with one entry per penetration.

D. Acceptance Standards

Check	Standard
Opening size	Matches the approved component; no oversized or undersized cuts
Backing and support	Structural backing or mounting block installed and fastened per the approved detail
Flashing sequence	Sill layer installed first, side layers overlap the sill layer, head layer overlaps side layers and integrates beneath the WRB above
Slope	Horizontal projections slope outward; no back-pitched shelf
Sealant location	Limited to the designated annular gap or joint; no sealing across a designed drainage or movement path
Clearances	Service-specific, combustion, electrical, and manufacturer access clearances maintained
Documentation completeness	Every penetration photographed and recorded on the penetration-flashing record before concealment

E. Review and Verification (Steps 1–5)

1. Review the penetration schedule, approved locations, service clearances, mounting-block details, WRB and flashing products, sealant requirements, and trade responsibilities. Confirm the revision date of the schedule against the project's document-control log.
2. Confirm that framing, structural panels, utilities, and required rough inspections are complete before cutting or enlarging openings. Verify the prior structural and rough-in inspection records before proceeding.
3. Identify each penetration by type: hose bibb, pipe, duct, vent, electrical box, conduit, cable, line set, or other approved service. Confirm the type against the penetration schedule for the assigned elevation.
4. Verify final penetration size, slope, support, projection, and relationship to siding and trim. Confirm the actual component dimension, not an assumed or nominal size.
5. Inspect the surrounding WRB, rainscreen, and backing for damage or incomplete work. Confirm the area is undamaged and ready before marking any cut.

F. Cutting and Backing (Steps 6–7)

1. Mark and cut only the opening required for the approved component. Confirm the cut will not damage wiring, piping, framing, flashing, or structural components before cutting.
2. Provide structural backing or an approved mounting block where the fixture or cover requires support. Fasten backing into structural framing using the specified corrosion-resistant fasteners.

G. Shingle-Lap Flashing Sequence (Steps 8–14)

1. Install a sill or lower flashing layer beneath the penetration or block so incidental water can drain outward. Extend the layer beyond the penetration by the distance specified in the flashing manufacturer's instructions.
2. Install side flashing layers that overlap the lower layer. Roll each layer for full adhesion at the flange edge.
3. Install the top flashing layer over the side layers and integrate it beneath the WRB above. Confirm the head layer is the last installed and the highest layer in the sequence.
4. For round penetrations, install an approved boot, gasket, split flashing, liquid flashing, or membrane collar. Confirm the accessory is sized to the actual penetration diameter.
5. For electrical boxes and rectangular blocks, flash the lower edge, jambs, and head in shingle-lap sequence. Use the same bottom-to-top order as sill, side, and head layers.
6. Maintain outward slope on horizontal projections and do not create a back-pitched shelf. Confirm slope with a level before covering the projection.
7. Seal the annular gap or designated joint using a compatible flexible system without blocking drainage or required movement. Limit sealant strictly to the location specified for that penetration type.

H. Clearances, Integration, and Documentation (Steps 15–20)

1. Maintain service-specific clearances, combustion requirements, electrical ratings, and manufacturer access. Verify each clearance against the current adopted code and manufacturer instructions.
2. Integrate furring, drainage mat, and siding support around the penetration. Confirm the rainscreen cavity remains continuous around the flashed opening.
3. Protect completed flashing until the exterior block, vent, or fixture is installed. Shield the flashing from foot traffic and incidental damage before Project 17 begins.
4. Inspect laps, adhesion, support, slope, drainage outlet, sealant, and WRB continuity. Confirm every layer against the Acceptance Standards table.
5. Correct oversized cuts, reverse laps, unsupported components, blocked drainage, and incompatible materials. Remove and redo any layer that fails inspection before continuing.
6. Photograph and document every concealed penetration-flashing detail. Label each photograph with its elevation, penetration type, and location.