Curbs & Flashings
Curbs & Flashings
Where almost every commercial leak actually starts.
Curb, Penetration and Flashing Repair in Winchester, KY
If you remember one thing about commercial roofing, make it this: the field of the membrane is rarely what leaks. Leaks happen at the details — everywhere the roof is interrupted by something sticking through it or turning up a wall.
Every penetration is a designed weak point
A flat expanse of membrane is a straightforward waterproofing problem. The difficulty is at every HVAC curb, vent, pipe, conduit, drain, skylight, and equipment support — each one a hole in an otherwise continuous surface, made watertight by a detail that has to be built correctly and maintained.
A typical commercial roof has dozens of them, and they are where the money should go during maintenance.
The details that fail most
- Pitch pans — filled pockets around irregular penetrations that shrink, crack, and need topping up; frequently forgotten entirely
- HVAC curb flashings — especially where units have been replaced and the curb reused
- Pipe boots — the collars crack with UV and thermal movement
- Base flashing at parapets — the termination bar and counterflashing above it
- Skylight curbs — the frame-to-curb joint as much as the roof detail
- Conduit and gas line supports — often set directly on the membrane and abrading it
Equipment changes create leaks
When an HVAC unit is replaced and the new unit does not match the old footprint, what frequently happens is an improvised adaptation — added sheet metal, sealant, whatever solves it that day. Those improvisations are among the most reliable leak sources on any commercial roof.
If you have had rooftop equipment replaced, those curbs are the first place worth looking.
Sealant is maintenance, not a repair
Every sealant has a service life and it is far shorter than the roof’s. A detail that depends on a bead of sealant to stay watertight is a detail that needs re-doing on a schedule.
A properly built detail sheds water by geometry — overlaps, counterflashing, drip edges — and uses sealant as a secondary defence. Detailing practice for commercial roofing is set out by the NRCA.
Common questions
What is a pitch pan and why does mine leak?
A metal pocket around an irregular penetration, filled with sealant. The fill shrinks and cracks over time and needs topping up — and it is almost always the forgotten item on a roof.
We replaced an HVAC unit and now it leaks.
Very common. If the new unit did not match the old curb, the adaptation is usually where the water is getting in.
Can these be fixed without replacing the roof?
Yes, almost always. Detail repairs are exactly the kind of work that extends a roof’s life for a fraction of replacement cost.
Why does sealant keep failing?
Because sealant is a consumable, not a permanent detail. If a joint relies solely on sealant, it needs rebuilding to shed water by geometry instead.
Related: skylight repair · leak detection · maintenance programmes · flat roof repair. Back to Winchester Commercial Roofing.
Winchester Commercial Roofing · Serving Winchester, Mount Sterling, Paris, Lexington & Clark County, KY · Call or text (859) 310-1209
Last updated August 2026
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