Commercial Roofing HVAC Curb Installation: What You Need to Know

Adding HVAC systems to a commercial roof isn’t as simple as setting a unit in place. Whether it’s a new construction, repair, or retrofit, the HVAC curb installation is a critical step that protects your roof, your equipment, and your investment.

Let’s break it down the way we do at The Roof Champion of Columbus—with no fluff, no upsells, just facts that protect your property.

What’s an HVAC Curb?

An HVAC curb is a framed, elevated platform that supports rooftop mechanical units like air conditioners, exhaust fans, or RTUs (roof top units).

It serves several purposes:

• Raises the unit off the roof to allow proper drainage.

• Distributes the equipment’s weight safely across structural supports.

• Provides a watertight, sealed transition between the roofing system and the HVAC unit.

If the curb is improperly installed or flashed, water finds its way in—and that leads to roof leaks, mold, rusted decking, and early failure of your roof system.

Why HVAC Curb Installation Must Be Done Right

Here’s what we’ve seen go wrong in Columbus and nearby cities:

• HVAC units placed directly on the membrane without a curb (yes, it happens).

• Poor curb flashing that leads to ponding water and interior leaks.

• Units installed without considering roof slope, drainage paths, or structural loading.

• Roofers and HVAC contractors pointing fingers when things go wrong.

At The Roof Champion, we coordinate directly with HVAC teams to make sure your curb is installed, sealed, and reinforced the right way—no gray areas, no shortcuts.

Key Parts of a Proper HVAC Curb Install

1. Structural Support

Your curb must sit directly on structural steel or framing members. We verify load paths to avoid sagging or cracks.

2. Code-Compliant Flashing

Flashing is the barrier that keeps water out. Per NRCA and IBC standards, curb flashing must:

• Extend at least 8” above the roof membrane surface.

• Be fully integrated with the roof’s waterproofing system.

• Use compatible materials (metal, modified bitumen, or membrane-specific materials).

We custom-fabricate curbs and flashings in-house when needed, especially for retrofits on older flat roofs across Powell, Dublin, and Westerville.

3. Roof Membrane Detailing

Whether your commercial roof is TPO, EPDM, mod bit, or metal, we tie the curb flashing into the existing system with:

• Seam welding (TPO/EPDM)

• Torch-applied or cold-adhesive flashings (mod bit)

• Counterflashing and sealant systems (metal roofs)

We follow the National Roofing Contractors Association specsand ARMA’s detailing best practices.

4. Drainage Planning

HVAC curbs that trap water cause pooling, membrane damage, and long-term failure. We slope all flashings away from the curb and verify drainage before signing off.

Retrofit vs. New Construction

New Builds:
We work with architects and GCs to coordinate curb placement with truss lines and insulation layers. Everything starts watertight and correct.

Retrofits:
Here’s where experience matters. We cut into existing roofs without compromising the system. That includes:

• Testing for trapped moisture around cut lines.

• Installing new blocking and support as needed.

• Re-flashing with full tie-in to original roof details.

Common Questions

How tall should an HVAC curb be?

Most local codes and manufacturers require a minimum 8" clearance above the finished roof surface, but we typically recommend 12" in snowy or debris-prone areas for safety and service access.

Can you install an HVAC unit without a curb?

No. Not if you care about your roof warranty, structural load distribution, or water resistance. A proper curb is non-negotiable.

Do you install the HVAC unit too?

We don’t install HVAC units—but we coordinate closely with your mechanical contractor to ensure the curb is watertight, level, and ready for equipment mounting.

Why Choose The Roof Champion for HVAC Curbs?

We’ve done this for churches in Hilliard, schools in Delaware, medical offices in Upper Arlington, and restaurants in Grove City.

No surprises. No leaks. No call-backs.

When Travis Haessly’s name is on the project, the curb isn’t just good—it’s bulletproof.

Need an HVAC curb installed on your commercial roof?

Call Travis directly at (614) 639-3422 or request a quote at
👉 www.roofchampcolumbus.com