Counterflashing is an important part of a commercial roofing system because it protects the roof-to-wall transition from water intrusion. On concrete walls, the counterflashing must be securely anchored while allowing the wall and roofing materials to accommodate normal movement. One of the most common installation methods is a reglet, a narrow groove cut into the concrete or masonry wall where the counterflashing is inserted and sealed.
What Is a Counterflashing Reglet?
A counterflashing reglet is a continuous or intermittent groove installed into a concrete wall to receive the top edge of metal counterflashing. The metal is inserted into the reglet and secured with an appropriate sealant or mechanical fastening system. This creates a weather-resistant transition that helps prevent rainwater from reaching the underlying roof membrane and wall assembly.
For commercial buildings, the reglet should be properly sized and positioned according to the counterflashing material, wall construction, roofing system, and project specifications.
Common Reglet Options for Concrete Walls
1. Saw-Cut Reglet
A saw-cut reglet is one of the most common options for concrete walls. A controlled horizontal cut is made into the concrete using a masonry or diamond-blade saw. The counterflashing is then inserted into the groove and sealed.
This approach provides a relatively clean installation and can work well when the concrete wall is accessible and structurally suitable for cutting. The groove must be deep and wide enough to securely receive the flashing without damaging the wall.
2. Surface-Mounted Reglet Systems
When cutting into a concrete wall is undesirable or impractical, a surface-mounted counterflashing system may be considered. In this configuration, metal components are attached directly to the wall using appropriate masonry fasteners and sealed along the upper edge.
Surface-mounted systems can be useful for retrofit roofing projects where minimizing concrete work is important. However, the attachment method must be designed to resist wind and water exposure.
3. Formed or Preinstalled Reglets
For new construction, a reglet can sometimes be incorporated into the concrete wall during construction using a formed recess or other planned detail. This can provide a consistent installation surface for counterflashing and reduce the need for cutting the finished concrete.
Preplanned reglets are particularly useful on projects where the roofing and wall details are coordinated before construction begins.
4. Reglet and Receiver Systems
Some commercial roofing assemblies use a dedicated receiver or reglet system that accepts the counterflashing. These systems can provide a more controlled attachment detail and may simplify future maintenance or replacement.
The exact configuration should be compatible with the roofing manufacturer’s requirements and the selected flashing material.
Which Option Is Best?
The best counterflashing reglet option depends on the existing concrete wall, roof assembly, building design, exposure to wind and rain, and whether the project is new construction or a roof replacement.
For an existing commercial building, a properly executed saw-cut reglet is often a practical choice when the concrete can safely be cut. For new construction, a formed or preplanned reglet can provide a clean and durable detail. Surface-mounted systems may be appropriate when cutting the wall is not feasible.
Why Proper Installation Matters
A counterflashing reglet is only effective when it is correctly installed and sealed. Poorly cut grooves, inadequate sealant, improper fasteners, or insufficient flashing engagement can create pathways for water intrusion. In Florida and other areas exposed to severe weather, the detail should also account for wind-driven rain and applicable building-code requirements.
Commercial property owners should have counterflashing inspected whenever roof leaks occur near wall intersections, coping, parapets, or other vertical transitions. Correctly designed and installed counterflashing helps protect the roof assembly, reduce moisture intrusion, and extend the service life of the commercial roofing system.
Bottom line: For concrete walls, common counterflashing reglet options include saw-cut reglets, formed or preinstalled reglets, surface-mounted systems, and dedicated receiver systems. The appropriate choice depends on the wall construction, roofing system, project conditions, and manufacturer’s installation requirements.
Related Questions
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