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Kitchen extraction cleaning - roof signs
Greasy, dark staining on the roof around the extract fan is easy to overlook - but it's a visible clue about what's happening inside the system. It usually means grease is passing right through the extraction and being discharged at the fan - a sign the system is grease-laden and likely overdue a clean. Here is what roof staining around the fan tells you, and what to do. This is general guidance.
The short answer
Most signs that an extraction system needs cleaning are inside (or in the kitchen). But there's one you can sometimes see from outside: greasy staining on the roof around the extract fan. It's easy to overlook, but it's a genuine clue about the state of the system. Here's what it tells you and what to do. This is general guidance. What the staining is. Greasy, dark staining on the roof around the extract fan means discolouration, greasy deposits, or dark streaking on the roof surface near where the fan discharges the extracted air. It's grease that has come out of the system at the fan and settled on the roof. What it tells you: grease is passing through. The key thing the staining tells you is that grease is passing right through the extraction system and being discharged at the fan. In a well-maintained system, the filters catch most grease at the canopy, and regular cleaning keeps the ductwork and fan clear - so relatively little grease reaches the discharge, and there's little roof staining. So heavy grease staining on the roof suggests the opposite: a lot of grease is getting through the system to the discharge. That points to a grease-laden system - the filters not catching enough (worn, wrong type, or overloaded), and grease built up through the ductwork and fan - which is very likely overdue a clean. So the staining is an external symptom of an internal problem: significant grease in the system, being carried through and discharged. It's the system telling you, from the outside, that it's greasy. Why it matters in itself. Beyond being a clue, the roof staining matters in its own right for two reasons. Mess and roof maintenance: grease discharging onto the roof is a mess, and can be a maintenance issue for the roof itself (grease on the roof surface, potentially around drainage). Fire risk at the fan: grease around the fan and on the roof adds to the fire risk at that end of the system - the greasy fan and surrounds being combustible (as covered in the roof-fan cleaning and overworked-roof-fan pages). So discharged grease isn't harmless. What to do. The right response is to treat roof staining around the fan as a prompt to act: get the extraction inspected and cleaned. The staining strongly suggests the system (filters, ductwork and fan) is grease-laden and due a clean - so an inspection will confirm the state, and a proper clean (the whole system, to TR19 Grease) will address the underlying grease (the fire risk and the poor performance) and, by clearing the system and sorting the filters, reduce the grease being discharged and staining the roof. It's also worth checking the filters (are they the right type, in good condition, and being cleaned often enough? - poor filters let more grease through). So don't ignore roof staining around the fan. It's a visible sign the system is greasy and likely overdue a clean - a useful external clue that saves you needing to see inside the ductwork. So read the sign and get the system inspected and cleaned. The takeaway. So greasy staining on the roof around the extract fan tells you grease is passing through the system and discharging - a sign of a grease-laden system that's likely overdue a clean (and a fire and mess concern in itself). Treat it as a prompt to get the extraction inspected and cleaned. So the roof is telling you the system needs cleaning - act on it. This is general guidance.
Key points
What the staining is
Greasy, dark staining on the roof around the extract fan means discolouration, greasy deposits or dark streaking on the roof surface near where the fan discharges the extracted air. It's grease that has come out of the system at the fan and settled on the roof around the discharge point - visible, if you look, as darkened, greasy marks on the roof.
It's easy to overlook, because it's up on the roof where nobody usually looks - but if you (or a contractor, or anyone up on the roof) notice it, it's a genuine and useful clue about the state of the extraction. Unlike most signs that a system needs cleaning (which are inside the ductwork, out of sight, or in the kitchen), roof staining is a sign you can sometimes see from outside - a window into what's happening within the system. So what the staining is - greasy marks where the fan discharges - is straightforward: grease that's come out at the fan and settled on the roof. What it tells you about the system inside is the valuable part, covered next. So it's discharged grease on the roof around the fan - a visible external clue. This is general guidance.
What it tells you
The key thing the roof staining tells you is that grease is passing right through the extraction system and being discharged at the fan. In a well-maintained system, the filters catch most grease at the canopy and regular cleaning keeps the ductwork and fan clear - so relatively little grease reaches the discharge, and there's little roof staining. Heavy grease staining on the roof suggests the opposite: a lot of grease is getting through the system to the discharge point.
That points to a grease-laden system: the filters not catching enough (worn, the wrong type, or overloaded and letting grease past), and grease built up through the ductwork and fan (so the system is carrying grease all the way through and out). Such a system is very likely overdue a clean. So the staining is an external symptom of an internal problem - significant grease in the system, being carried through and discharged. It's the system telling you, from the outside, that it's greasy inside (as covered in why a greasy filter lets grease reach the whole system). This makes roof staining a valuable clue: it lets you infer the internal state without seeing into the ductwork. So what it tells you - grease is passing through the system - is the important message: heavy roof staining means a grease-laden system that needs cleaning. So read the staining as a sign of a greasy, overdue system. This is general guidance.
Why it matters in itself
Beyond being a clue to the internal state, the roof staining matters in its own right, for two reasons. Mess and roof maintenance: grease discharging onto the roof is a mess, and can become a maintenance issue for the roof itself - grease on the roof surface, potentially getting into or around roof drainage, and generally soiling the roof. So it's an unwanted deposit that affects the building. Fire risk at the fan: grease around the fan and on the roof adds to the fire risk at that end of the system - the greasy fan and its surroundings being combustible material in a spot (up on the roof, near the structure) where a fire is dangerous and hard to reach (as covered in the roof-fan cleaning and overworked-roof-fan pages).
So the discharged grease isn't harmless - it's both a mess on the building and a contribution to the fire risk at the fan and roof. This adds to the reasons to act on roof staining: it's not just a diagnostic sign of an internal problem, but a problem in itself at the discharge end. Cleaning the system (and sorting the filters so less grease gets through) addresses both - reducing the discharge that stains and greases the roof, and cleaning the greasy fan and surrounds. So why it matters in itself - roof mess and fire risk at the fan - reinforces that roof staining shouldn't be ignored: it signals a greasy system and represents a grease problem at the roof. So the staining is both a warning and a problem to address. This is general guidance.
What to do
The right response to roof staining around the fan is to treat it as a prompt to act: get the extraction inspected and cleaned. The staining strongly suggests the system (filters, ductwork and fan) is grease-laden and due a clean - so an inspection will confirm the state of the system, and a proper clean (the whole system, to the TR19 Grease standard) will address the underlying grease: the fire risk (removing the grease throughout, including the greasy fan and roof-end), and the poor performance (a grease-laden system extracts poorly). And by clearing the system and sorting the filters, the clean will reduce the grease being discharged and staining the roof going forward.
It's also worth checking the filters as part of this: are they the right type, in good condition, and being cleaned often enough? Poor, worn, wrong-type or under-cleaned filters let more grease past into the system and through to the discharge - so improving the filters (cleaning them properly, replacing worn ones) helps reduce the grease getting through and staining the roof (as covered in the filter pages). So the action is: get the system inspected and cleaned (to address the grease it's clearly carrying), and check the filters (to reduce grease getting through in future). So what to do - get the system inspected and cleaned - is the practical response to roof staining: the sign is telling you the system needs cleaning, so act on it. So book an inspection and clean, and check the filters. This is general guidance.
Read the sign
So greasy staining on the roof around the extract fan is a valuable external clue: it tells you grease is passing through the system and being discharged - a sign of a grease-laden system that's likely overdue a clean (and a fire and mess concern in itself). The roof is telling you, from the outside, that the system needs cleaning. Read the sign and act on it.
The practical value of this sign is that it's visible without opening up the ductwork - so it's a clue anyone who notices it (you, staff, a roofer, a contractor) can act on. If you see (or are told about) greasy staining on the roof around your fan, take it as a strong hint that the extraction is grease-laden and due a clean, and get it inspected and cleaned (and the filters checked). Don't dismiss it as just weathering or dirt - greasy, dark staining specifically around the fan discharge is grease from your system. So read the sign - the roof is telling you it's overdue - is the takeaway: roof staining around the fan is the system flagging, externally, that it's greasy and needs attention. Act on it, and you catch a grease-laden system (and control the fire risk) before it gets worse. So treat roof staining as a prompt, and get the extraction cleaned. This is general guidance.
Questions
It usually means grease is passing through the extraction and discharging at the fan - a sign the system is grease-laden (filters not catching enough, grease built up through the ductwork and fan) and likely overdue a clean. Greasy, dark staining on the roof around the extract fan is grease that has come out of the system at the fan discharge and settled on the roof. It tells you grease is passing right through the extraction system and being discharged. In a well-maintained system, the filters catch most grease and cleaning keeps the ductwork and fan clear, so little reaches the discharge and there's little staining. So heavy roof staining suggests a lot of grease is getting through - pointing to a grease-laden system (filters worn, wrong or overloaded; grease built up through the ductwork and fan) that's very likely overdue a clean. So the staining is an external sign of an internal problem: significant grease in the system, being carried through and discharged. It's a prompt to get the system inspected and cleaned. So it means grease is passing through - the system is greasy and due a clean. So a grease-laden system, overdue cleaning. This is general guidance.
Yes - grease on the roof is a mess and a maintenance issue for the roof, and grease around the fan and on the roof adds to the fire risk at that end; so it matters both as a clue and as a problem to address. Roof staining around the fan matters both as a diagnostic clue (of a grease-laden system) and as a problem in its own right. Mess and roof maintenance: grease discharging onto the roof soils the roof surface and can become a maintenance issue (grease around roof drainage, on the structure). Fire risk at the fan: grease around the fan and on the roof adds to the fire risk at that end of the system - the greasy fan and surrounds being combustible, in a spot (up on the roof, near the structure) where a fire is dangerous and hard to reach. So the discharged grease isn't harmless - it's both a mess on the building and a contribution to the fire risk at the fan and roof. Cleaning the system (and improving the filters) addresses both, reducing the discharge and cleaning the greasy roof-end. So yes - it's a mess and a fire-risk concern, not just a sign. So yes; roof mess and added fire risk. This is general guidance.
Treat it as a prompt to get the extraction inspected and cleaned - it signals a grease-laden system due a clean; a proper clean addresses the grease inside and reduces the discharge, and check the filters too (poor filters let more grease through). If you see (or are told about) greasy staining on the roof around your extract fan, treat it as a prompt to act. The staining strongly suggests the system (filters, ductwork and fan) is grease-laden and due a clean, so: get the extraction inspected (to confirm the state) and cleaned (the whole system, to the TR19 Grease standard) - which addresses the underlying grease (the fire risk and the poor performance) and, by clearing the system, reduces the grease being discharged and staining the roof. And check the filters: are they the right type, in good condition, and cleaned often enough? Poor or under-cleaned filters let more grease through, so improving them helps reduce the grease getting through in future. So the action is: get the system inspected and cleaned, and check the filters. Don't dismiss the staining as weathering - greasy marks around the fan are grease from your system. So get it inspected and cleaned, and check the filters. So act on it - inspect, clean, check filters. This is general guidance.
General weathering exists, but greasy, dark staining specifically around the fan discharge is characteristically grease from your system - so treat that pattern as a grease sign and get the extraction checked rather than dismissing it. Roofs do weather and get generally dirty, so not all roof marks are grease. But greasy, dark staining specifically concentrated around the extract fan discharge is characteristic of grease that's come out of the system - it has a greasy quality and a location (around the fan) that distinguish it from general weathering or dirt elsewhere on the roof. So while you shouldn't assume every roof mark is grease, greasy staining patterned around the fan discharge should be treated as a grease sign - it's exactly where discharged grease would settle, and its greasy nature gives it away. The safe approach is not to dismiss it: if there's greasy, dark staining around the fan, get the extraction inspected (which will confirm whether the system is grease-laden, as the staining suggests). Better to check and find the system needs cleaning than to dismiss a real sign. So greasy staining around the fan is characteristically grease - get it checked. So probably grease if it's greasy and around the fan; check it. This is general guidance.
The filters catch grease at the canopy, but if they're worn, the wrong type, overloaded or under-cleaned, more grease gets past into the system and through to the discharge; heavy roof staining suggests the filters aren't catching enough and the system is grease-laden. The filters are meant to catch most grease at the canopy, so in a well-maintained system little grease should reach the discharge. If grease is reaching the roof in quantity (heavy staining), it suggests the filters aren't catching enough - because they're worn, the wrong type for the cooking, overloaded (grease-saturated), or not being cleaned often enough - so grease gets past them into the ductwork, builds up through the system, and passes out at the fan (as covered in why a greasy filter lets grease reach the whole system). It also reflects a grease-laden system generally (grease built up through the ductwork and fan). So heavy roof staining points to both a filter issue (not catching enough) and a system due a clean. The fix is to clean the system and address the filters - clean them properly, replace worn ones, and check they're the right type and cleaned often enough - so less grease gets through. So the filters aren't catching enough - check and improve them, and clean the system. So because the filters are letting grease past; check them. This is general guidance.
Largely yes - a proper clean removes the grease the system is carrying and discharging, and sorting the filters reduces grease getting through, so far less reaches the roof; regular cleaning keeps it that way. Cleaning the system will largely address the roof staining, by tackling its cause. A proper clean (the whole system, to the TR19 Grease standard) removes the grease built up through the filters, ductwork and fan - so the system is no longer carrying and discharging significant grease, and far less reaches the roof. Sorting the filters as part of this (cleaning them properly, replacing worn ones, ensuring the right type and frequency) reduces the grease getting past them into the system in the first place - the root of grease reaching the discharge. So after a proper clean and with good filters, the grease discharge (and the roof staining it causes) is much reduced. Keeping the system cleaned regularly (at the right frequency) and the filters well-maintained keeps it that way - preventing the grease building up again and reaching the roof. So yes - cleaning and good filters largely stop the staining, and regular cleaning keeps it stopped. So yes; a clean and good filters greatly reduce it. This is general guidance.
Greasy roof staining around the fan signals a grease-laden system passing grease through to discharge; we inspect and clean the whole system to TR19 Grease - and check the filters - addressing the grease inside and reducing what reaches the roof. Ask us to inspect and clean your extraction. This is general guidance.
