A recent project at Flat Rock Middle School required a coordinated effort to prepare the facility for eight brand-new rooftop HVAC systems.
Once the initial roof penetrations were cut and framed, the WNC Roofing crew stepped in to handle the critical next phase: installing the new 5’ x 7’ open-top curbs and sealing them completely before the new mechanical units were crane-lifted into place.
Here is an overview of our installation process and how we structure our workflow to keep commercial project sites moving efficiently.
The Curb Installation and Flashing Process
Because these were new HVAC units, the curbs remained open at the top during our phase of the project. This allowed our crew to achieve complete encapsulation, creating a seamless waterproofing barrier from the structural deck up.
1. The Butyl Gasket Under-Seal
Before anchoring the metal curb, we placed a defense layer at the base. We apply a continuous, heavy bead of premium butyl caulk directly beneath the flanges of each 5’ x 7’ curb.
- This creates a pressurized gasket seal between the metal curb and the roof deck, preventing moisture from driving underneath the flange during high-wind rain events.
2. High-Load Mechanical Anchoring
Once the curb is perfectly positioned over the penetration, it must be integrated into the building’s frame. We mechanically fasten the flanges using heavy-duty roofing screws spaced precisely 12” on center (OC).
- This strict fastening pattern ensures the curb meets wind-uplift regulations and is fully rated to support the physical weight of the incoming HVAC unit.
3. Vertical Membrane Adhesion
With the structural curb locked down, we transition to the roofing membrane (TPO/PVC/EPDM). We apply a high-strength adhesive to the outside sides of the curb and pull the membrane up the vertical walls, covering heights up to 18 inches.
- This eliminates vulnerable seams at the high-stress, right-angle joints where the horizontal roof deck meets the vertical curb wall.
4. Inside-Lip Securement
We folded the membrane completely over the top lip of the curb and secured it on the inside.
- Wrapping the material over the top edge fully encapsulates the structure. When the rigging crew drops the new HVAC unit onto the frame, it sits on a completely wrapped, weather-tight saddle.
Maximizing Project Efficiency Through Job Site Flexibility
In commercial construction, rigid contractors cause project bottlenecks. We design our production workflow to remain highly collaborative, organized, and adaptive to moving construction timelines.
- We began our flashing work on a weekday morning immediately after the roof deck preparations were finalized. Our on-site production hours ran from 8:30 AM to 4:30 PM, maximizing daylight and aligning cleanly with ongoing facility operations.
- WNC Roofing provides all necessary licensing, insurance, and premium manufacturer-warranted materials upfront to ensure complete compliance with zero project delays.
- By clearly defining our scope and keeping specialized tasks handled by others (such as crane rigging, interior cleanup, or attachment through insulation greater than 5”), we keep our team lean, fast, and entirely out of the way of other trades.
The Bottom Line
A successful commercial build relies on a roofing partner who delivers technical accuracy without logistical friction. By securely setting the curbs, utilizing high-grade under-seals, and wrapping the membrane completely over the open tops, WNC Roofing ensured Flat Rock Middle School’s new climate systems sit on a durable, leak-free foundation.
See More of Our Commercial Work
Explore our Projects Page to see how WNC Roofing handles complex commercial installations, facility upgrades, and membrane roofing solutions across the region.
Partner with WNC Roofing for Your Next Upgrade
Planning an HVAC replacement or a new commercial build? Ensure your infrastructure is protected by a team that prioritizes precision and schedule flexibility. Reach out to us via our Contact Us page today to request a detailed project estimate or discuss your specific scope of work.
