Rooftop grease containment: what it is and why landlords and roofers care
Your exhaust fan slings grease. Without a containment system it lands on the roof membrane, where it eats the roof, voids warranties, and sits as fuel next to the fan. What containment is, what the code says, and who ends up paying when it is missing.
Rooftop grease containment is a collection system fitted around the base of a kitchen exhaust fan that catches the grease the fan discharges before it reaches the roof. NFPA 96 section 7.8.2.1 requires rooftop terminations to have a noncombustible, closed, rainproof grease collection container, along with a hinged upblast fan with flexible weatherproof cable [1]. Without it, grease runs down the fan curb and pools on the roof, where it degrades the membrane, creates a slip and fire hazard, and eventually shows up as a roofer's photo in your landlord's inbox.
This guide covers where the grease comes from, what it does to a roof, what the code requires, and why the person asking about containment is often not the person who runs the kitchen.
Why is there grease on my roof?
Because the fan puts it there. A kitchen exhaust system moves grease vapor from the cooking line through the hood, the duct, and out an upblast fan on the roof. The filters catch some. The plenum and duct collect more as the vapor cools. Whatever is still airborne at the fan drops out in the fan bowl, and whatever the bowl cannot hold gets slung out the discharge and runs down the outside of the fan.
The amount depends on the cooking. A charbroiler, a wok range, or a fryer bank throws far more grease than a soup kettle, which is why NFPA 96 tiers inspection by cooking type, from monthly for solid fuel to annually for low-volume [1]. A high-volume kitchen with no containment can put a visible grease shadow on the roof within a season. Our crews see roofs where the membrane around the fan has been soft for years and the stain has spread several feet from the curb.
What does grease do to a roof?
Three things, and each one has a different person worrying about it.
It degrades the membrane. Most commercial roofs in Oregon and Washington are single-ply membrane (TPO, PVC, EPDM) or modified bitumen. Cooking grease is a solvent for many of these materials. It softens the membrane, breaks down the seams, and lets water in. Roofers treat grease contamination as damage caused by the tenant's equipment, and roof manufacturers commonly exclude chemical contamination from the warranty. That is the roofer's problem first and the landlord's problem second.
It is a slip and fire hazard. A greasy roof is slick when wet, which in this part of the country is most of the year, and it is the surface every technician (HVAC, roofer, our crews) walks on to get to the equipment. It is also a fuel load sitting next to the fan discharge. Cooking equipment caused over 60 percent of fires in eating and drinking establishments between 2014 and 2018 in the NFPA's data [2], and a fire that climbs the duct arrives at a fan sitting in a puddle of grease.
It contaminates runoff. Grease on a roof ends up in the roof drains and the storm system. Some municipalities and some property managers treat that as a discharge issue on its own.
Who is responsible for grease on the roof, tenant or landlord?
Usually the tenant, in practice. Most commercial restaurant leases put maintenance of the kitchen exhaust system, and any damage caused by it, on the tenant, and landlords enforce it [3]. The roof itself is usually the landlord's, which is exactly why they care: the tenant's fan is damaging the landlord's asset. So the sequence goes like this. The roofer is on the roof for an unrelated leak, photographs the grease around the fan, and sends it to the property manager. The property manager sends it to the tenant with a letter citing the lease. The tenant calls a hood cleaner.
If you are the tenant, containment plus cleaning is a lot cheaper than a roof repair bill and a lease dispute. If you are the landlord or property manager, requiring containment on every kitchen exhaust fan in the building is the single cheapest thing you can do to protect the roof. Either way, our rooftop grease containment service is the fix, and it goes in on the same visit as a cleaning.
What does NFPA 96 require for rooftop grease?
Section 7.8.2.1 covers rooftop terminations. It requires a noncombustible, closed, rainproof grease collection container, and it calls for the upblast fan to be hinged with flexible weatherproof electrical cable so it can be tipped back for cleaning [1]. Section 8.1.6.3 separately requires access to the fan for cleaning, with a minimum access opening of 3 by 5 inches or 4 inches round [1].
Read those two together and you get the rooftop package a fire inspector expects to see: a hinged fan, a containment system, and a roof that is not coated in grease. Oregon adopts NFPA 96 through Section 606 of the Oregon Fire Code [4], and Washington through WAC 51-54A-0606, which requires the system to be operated, inspected, and maintained per NFPA 96 Chapter 12 [5]. Portland's FIR-8.08 goes further on the paperwork, requiring cleaning at set intervals by cooking type and records kept on site for the Fire Marshal [6]. An inspector who goes on the roof and finds no containment and a grease-soaked curb has two findings before opening anything.
Roofer or landlord sent you a photo? Get a free estimate for containment on your next cleaning, or call (800) 973-5573. We install it on the same visit.
What is a rooftop grease containment system?
The common design is a tray or box that sits on the fan curb around the base of the fan, with an absorbent filter pad inside. Grease running down the fan drains into the tray, the pad soaks it up, and rainwater passes through a hydrophobic layer and drains off. The pad gets replaced on a schedule, usually at each cleaning, which is why containment and cleaning belong to the same vendor.
The key features to look for:
- Closed and rainproof, so the tray does not become a bathtub of grease and water that overflows onto the roof.
- Noncombustible construction, as NFPA 96 requires [1].
- Sized to the fan curb, not a generic box propped underneath.
- A pad that can be changed without removing the fan.
- Compatible with a hinge kit, so the fan still tips back for cleaning.
A grease box that never gets its pad changed is not containment. It is a full bucket next to a fan. That is the maintenance side of the job, and it rides along with exhaust fan preventative maintenance on every visit.
What about the hinge kit?
The hinge is the other half of the rooftop package, and the two get installed together for a reason. Without a hinge, a fan has to be unbolted and lifted off the curb to clean the bowl, which is how wiring gets torn and how fans end up "cleaned" with the bowl untouched. With a hinge, the fan tips back on a hold-open arm and the bowl, blades, and the containment tray are all reachable. NFPA 96 calls for hinged upblast fans with flexible weatherproof cable at the rooftop termination [1]. Our crews install exhaust fan hinge kits whenever a fan does not have one, because every future cleaning and every future repair is faster with it.
What should a landlord or property manager require?
If you own or manage buildings with restaurant tenants, three lease-level requirements will save you a roof.
- Containment on every kitchen exhaust fan, maintained by the hood cleaning vendor, with the pad change on the cleaning report.
- A hinge kit on every upblast fan, so the fan gets cleaned instead of lifted.
- A copy of each cleaning certificate and photo report, including the roof photos, sent to property management after every service. The report is required under NFPA 96 sections 12.6.14 and 12.6.15 within two weeks anyway [1]; you are just asking to be on the distribution.
The roof photo is the one that matters to you. If the tenant's cleaner never goes on the roof, there are no roof photos, and that is your answer. A full commercial hood cleaning from our crews includes the roof on every visit, and for property managers with several restaurant tenants we can put every fan in a portfolio on one schedule.
Frequently asked questions
Is rooftop grease containment required by code?
NFPA 96 section 7.8.2.1 requires a noncombustible, closed, rainproof grease collection container at rooftop terminations [1]. Oregon and Washington adopt NFPA 96 through their fire codes [4][5]. Fire inspectors who go on the roof look for it.
How much grease can an exhaust fan put on a roof?
Enough to soften a membrane. High-volume kitchens (charbroilers, woks, fryer banks) can leave a visible stain within a season. NFPA 96 sets the cleaning trigger in the fan housing at 0.125 inches [1], and whatever the housing cannot hold ends up on the roof.
Who pays for roof damage from kitchen exhaust grease?
Read the lease, but most commercial restaurant leases assign the exhaust system and the damage it causes to the tenant [3]. Containment costs a fraction of a membrane repair.
How often does the containment pad need changing?
At every cleaning is the usual schedule, more often for high-volume kitchens. A saturated pad stops working and the tray overflows. Ask for the pad change to be noted on the cleaning report.
Can grease containment be installed on my existing fan?
In almost every case, yes. Containment systems are sized to the fan curb. Our crews measure the curb on the first visit and install on the same trip as a cleaning, usually along with a hinge kit if the fan does not have one.
Does grease containment replace cleaning the fan?
No. Containment catches what the fan discharges. The fan bowl and blades still load with grease and still need to be cleaned to remove combustible contaminants under NFPA 96 [1]. The two go together.
Protect the roof and pass the rooftop inspection on one visit. Get a free estimate with your address and hood count, or call (800) 973-5573 any hour.
Sources
- NFPA 96 summary (7.8.2.1 rooftop grease collection container and hinged fan, 8.1.6.3 fan access, Table 12.4, 12.6.1.1 fan housing threshold, 12.6.14 and 12.6.15 reports), Facilitec Southwest (facilitec-sw.com, facilitecwest.com)
- Ansul, "Two NFPA restaurant fire stats," citing NFPA data for 2014 to 2018 (ansul.com)
- SVN Bluestone, restaurant tenants and grease system responsibilities in commercial leases (svnbluestone.com)
- Oregon Fire Code 2022, Chapter 6, Section 606 (up.codes)
- Washington Administrative Code 51-54A-0606, Section 606.3 (app.leg.wa.gov)
- Portland Fire and Rescue policy FIR-8.08 (portland.gov)