Guide
Grease leaking from the rooftop fan: causes and who to call
A black halo on the roof membrane around the exhaust curb is not a mystery stain. Grease that should have drained into a receptacle is landing on the roof instead. That is a fire-fuel issue under the rooftop termination rules, a roof-warranty issue for the landlord, and usually a maintenance miss — not something a canopy wipe fixes.
Short answer
Secondary NFPA 96 summaries require rooftop terminations to drain grease from fan/duct low points into a noncombustible, closed, rainproof collection container (§7.8.2.1), and upblast fans to drain to a readily accessible, visible grease receptacle not over 1 gallon (§8.1.2.3). Leaks usually mean: overflowing or missing cup, clogged drain, hinge/containment misalignment, heavily loaded fan housing, or a cracked curb seal. Empty or replace the cup first if that is the only problem; call the hood cleaner for a full-system clean and housing drain check; call HVAC/sheet metal for hinge, curb, or drain repairs; call the roofer for membrane damage. Replace missing, broken, distorted, or leaking metal grease containers (NFPA 96 2027 FR language §12.6.17.1).
Common causes (walk the roof before you call)
| What you see | Likely cause | First call |
|---|---|---|
| Cup full to the rim; fresh grease ring under the drain | Nobody emptied the receptacle between cleans | Staff empties/replaces cup now; hood cleaner if housing is also loaded |
| No cup at all; grease streaking down the curb | Missing receptacle; drain dumping on the roof | Hood cleaner / sheet metal to install a proper ≤1 gal receptacle |
| Cup empty but grease weeping from housing seams | Clogged fan drain tube; grease bypassing the drain | Hood cleaner (open fan, clear drain) — needs hinge access |
| Grease on roof after every clean | Containment pad blocking hinge or drain misaligned after retrofit | Same company that did hinge or containment — they have to work together |
| Heavy grease inside fan bowl; cup overflows in days | Duct/fan overdue for cleaning; high grease load | Hood cleaner for full-system clean; tighten inspection interval |
| Cup cracked, bent, or leaking at the seam | Damaged container | Replace the container (code direction for missing/broken/distorted/leaking metal grease containers) |
| Grease under curb flashing; membrane soft or stained far from the drain | Curb seal failure or long-term overflow | Roofer for membrane; cleaner for source control |
| Fan welded flat; never opens | No hinge/hold-open — housing and drain never serviced | HVAC/sheet metal for hinge kit; then cleaner. See hinge checklist |
What the code is aiming at
- Drain path: grease from traps and low points at the rooftop termination goes into a noncombustible, closed, rainproof, structurally sound collection container that will not sustain combustion and that does not hurt fan performance (secondary §7.8.2.1(4)–(6))
- Fan receptacle: upblast fans drain to a readily accessible, visible grease receptacle not exceeding 1 gallon (secondary §8.1.2.3)
- Access: hinged upblast fan with flexible weatherproof cable and hold-open retainer so the housing and drain can be cleaned (secondary §7.8.2.1(8) / §8.1.1.1)
- Depth in the fan: fan housings have a higher grease-depth cleaning trigger than other surfaces in recent NFPA revisions (0.125 in / 3175 μm in fan housings vs 0.078 in elsewhere — secondary). See grease depth thresholds
Emptying the cup is maintenance. It does not replace a duct and fan clean. A pretty containment pad does not excuse a missing cup. See inspection points and containment overview.
Who to call (split the jobs)
| Job | Who | Not who |
|---|---|---|
| Empty/replace cup; wipe curb grease after source is fixed | Kitchen staff or cleaner on the next visit | Do not wait for the next semi-annual if the cup is overflowing now |
| Full-system clean; clear fan drain; photo housing and blades | Hood / exhaust cleaner acceptable to your AHJ | Not a pressure-washer who only does the canopy |
| Install hinge kit, new drain tube, curb work, duct repair | HVAC / sheet metal / listed fan installer | Not the grease-trap pumper |
| Roof membrane repair; warranty claim photos | Roofer / building engineer | Not the cleaner’s chemical wash alone |
| Citation for grease on roof / missing receptacle | Close it with the cleaner + hardware fix; show the inspector photos | See reinspection notices |
Operator checklist the night you find a leak
- Photo the cup, drain, curb, and stained roof before anyone cleans it up
- Empty or replace the cup if it is full; note the date
- Confirm the fan can hinge open; if not, that is a separate work order
- Book a full-system clean with rooftop fan photos required in the report
- Tell the landlord if the membrane is stained — roof warranties care about grease
- Ask whether larger listed containment (often cited under UL 710A) is needed after the source is fixed
Who it’s for / not for
- For: GMs and facilities leads who found grease on the roof; multi-unit operators comparing sites; landlords reviewing roof claims tied to kitchen exhaust
- Not for: designing a new exhaust system from scratch; grease-trap / interceptor pumping (different drain, different vendor); electrical faults on the fan motor (HVAC)
Sources
- Facilitec Southwest: NFPA 96 section guide (secondary excerpts §7.8.2.1 rooftop containment; §8.1.6.3 fan access; §12.6.17 grease drip containers)
- Facilitec Southwest: Exhaust fan hinge kit (hinge vs containment alignment; drain must land in collection when closed)
- NFPA 96 First Revisions report (A2026) (FR-52 depth thresholds; FR-13 new §12.6.17.1 replace missing/broken/distorted/leaking metal grease containers)
- HoodFilters: NFPA 96 secondary excerpts (§8.1.2.3 ≤1 gal receptacle; §7.8.2.1 rooftop termination)
Next step
Photo the cup and the stain tonight. If the cup is full, empty it. If there is no cup or the fan does not hinge, get those work orders out before the next fire walk.