Of the five points that stop a restaurant opening, four can be negotiated. You find an arrangement, you pay, you wait, you argue. Extraction cannot.
It is the one place in the project where a meeting of the building's co-owners can say no, and where that no is final. Not expensive: impossible.
What the rule actually requires
The fumes, grease and smells of a professional kitchen must be discharged above the roof. This comes from the règlement sanitaire départemental — the departmental public-health regulation, modelled on a national template and published by your prefecture.
The word that matters is above. Not "outside", not "through the front wall", not "into the courtyard". A flue that comes out at head height in a courtyard sends your frying smells into the first-floor windows, and you will have nothing to say to the neighbour who complains.
Why the owners' meeting decides
An extraction flue does not stay inside your premises. It crosses floors, ducts, a façade, a roof — that is to say, parties communes, the building's common parts. And you have no right to touch those on your own.
Creating or altering that flue therefore requires authorisation from the assemblée générale, the general meeting of co-owners, carried by a reinforced majority. And a general meeting is not a service desk: it is a gathering of people who live above your future kitchen and who have nothing to gain from it.
The reasons for refusing are rarely bad faith, incidentally. A flue takes up room in an already crowded duct, damages a listed façade, makes noise, is hard to clean. A reasonable co-owner can vote no for good reasons.
Three questions to ask before talking money
1. Is there a flue, and does it serve my unit?
Those are two questions, not one. A building may have a flue that belongs to another unit, or that was allocated to a specific use thirty years ago. The syndic — the managing agent — knows, or can find it in the co-ownership rules and the plans.
2. Is it sized for my kitchen?
A flue designed for a bakery is not a flue for a rotisserie. The airflow depends on what you cook and on the power installed. A building-services engineer or a kitchen fitter answers that, not an estate agent — and the answer takes one visit.
3. Is it in working order?
A flue that has been idle for five years may be caked, holed, or non-compliant with current rules. Bringing it back into service costs less than building one, but it is not free.
What to write into the contract
Extraction is settled with a condition suspensive, a condition precedent. It is one line in a deed, it costs nothing, and it gives you your money back if the answer is no.
Put plainly: the sale or the lease only becomes final if the general meeting authorises the extraction works, or if a survey confirms that the existing flue suits the intended activity.
A seller acting in good faith will accept it. A seller who refuses it has told you something, and that is useful in itself.
The timetable, which is the real trap
An ordinary general meeting is held once a year. An extraordinary one can be called, but it has to be paid for and it takes time.
In other words: if your project depends on a vote, your opening date no longer depends on you. It depends on when the managing agent convenes the co-owners, and on what they decide that day.
That is why this question comes before all the others. Not because it is the most complicated — because it is the only one whose answer can be a permanent no.