“Which diagnostics are mandatory when selling?” — the question often comes from French law and its dossier of technical diagnostics. The Swiss answer is different, and simpler than one might think: only one check is required by law when selling — the OIBT electrical inspection. Everything else falls under recommended, contextual… or French law, which does not apply here. Here is the breakdown, point by point.
The mandatory item: the OIBT electrical inspection
The federal ordinance on low-voltage installations (OIBT) requires a periodic inspection of electrical installations — every 20 years for dwellings — confirmed by a safety report. The rule that concerns a sale: in the event of a change of owner, a new inspection is required if the last one is more than five years old. In practice, the seller hands over the safety report to the buyer; if it is too old or cannot be found, the inspection is ordered before completion — and any defects found are corrected or negotiated. This is the only “diagnostic” that the law makes a condition of the transfer.
Two clarifications that avoid unpleasant surprises. First, it is up to the owner to ensure the inspection is carried out — not the distributor. In Geneva, SIG invites the owner to present their report, but the distributor is not obliged to be notified of a change of owner: the distributor may well be unaware that the property has changed hands, and the obligation does not lapse as a result. Second, the purpose of the rule is explicit: that whoever acquires a building without knowing its history receives an installation in compliance, because they will henceforth bear the liability of a building owner within the meaning of Article 58 of the Code of Obligations. The safety report is not an administrative formality — it is the transfer of a liability.
One exception exists: a building sold subject to renovation may dispense with the report, under strict conditions — the renovation must notably concern the electrical installations themselves, not merely the rest of the building. In other words, one cannot be exempted simply by announcing “works” in general terms.
The CECB: not mandatory in Geneva — but often decisive
Contrary to a widespread belief — and unlike the canton of Vaud — Geneva does not require a CECB for a sale: the cantonal energy certificate for buildings is only mandatory there to obtain certain energy subsidies (from CHF 10,000, in the form of CECB+). But “not mandatory” does not mean “useless”: at a time when energy performance weighs on every purchase decision and on financing terms, a recent CECB documents the property, defuses negotiations over energy, and speeds up the buyer’s bank assessment. Geneva also has its own mechanism: the IDC — the heat consumption index, which owners of heated buildings declare each year to the State; above the set threshold, renovation works become mandatory. A buyer of a building will look at the IDC before anything else.
Asbestos: the duty of transparency
Asbestos has been banned in Switzerland since 1990: for any building built before 1991, its presence is possible — sprayed coatings, false ceilings, adhesives, ducts. At the point of sale, the diagnostic is not a legal obligation, but two rules make it almost unavoidable: a pre-works diagnostic is required as soon as renovation affects a pre-1991 building — a buyer planning works will therefore commission one — and above all, a seller who knows of the presence of asbestos and conceals it commits a concealment that the law penalises severely: the warranty against defects is never excluded in the event of fraud. A recent report therefore protects the seller first and foremost. Its validity follows common sense: with no asbestos detected, it remains valid as long as the building is not altered; with asbestos present in good condition, it holds until the first works project.
Radon, lead, gas: fact versus fiction
Radon — a naturally occurring radioactive gas that accumulates in basements — is the subject of official maps by municipality: a measurement is recommended for inhabited basement rooms and lower ground floors, and solutions (ventilation, sealing) are well proven. Lead concerns paintwork in older buildings — typically pre-1970: no sale diagnostic is required in Switzerland, but a survey is prudent before works in an older property. Gas, finally: the “gas diagnostic of less than three years” that one reads everywhere is a French rule — in Switzerland, gas installations are subject to periodic checks by distributors, not to a sale diagnostic. Beware of imported checklists: they make you spend money for nothing.
The IDC: the Geneva threshold that triggers works
This is the Geneva particularity that imported checklists overlook, and it is the only one that can prove costly. The heat consumption index measures what a building actually consumes to heat itself, relative to its surface area. Geneva sets a compliance threshold at 125 kWh/m²·year, i.e. 450 MJ/m²·year. Above this, the owner is no longer free to do nothing.
The canton distinguishes two levels. Between the compliance threshold and the notable exceedance threshold, the building must undergo an energy audit and improvement measures. Beyond the notable exceedance, the owner is under an obligation to carry out energy renovation works to bring consumption back below 125 kWh/m²·year.
And this second threshold is set to fall, according to an already established schedule:
- 222 kWh/m²·year (800 MJ) until the end of 2026;
- 180 kWh/m²·year (650 MJ) from 1 January 2027;
- 153 kWh/m²·year (550 MJ) from 1 January 2031.
Read this schedule as a buyer would: a building at 200 kWh/m²·year is currently outside the works obligation, but will fall within it in 2027. This is not a theoretical risk, it is a date. The IDC should be checked before making an offer, not after completion — and it is negotiable, because it quantifies a future expense on a building you have not yet paid for.
What the seller truly owes the buyer
Swiss law does not draw up a list of diagnostics: it sets a principle — conceal nothing. Geneva deeds almost always exclude the warranty against defects, and this exclusion holds… except for what the seller knew and kept quiet. Diagnostics are therefore as much the seller’s insurance as they are information for the buyer: documenting the condition locks in the warranty exclusion. On the buyer’s side, the logic is the mirror image: since few checks are mandatory, the pre-purchase inspection remains their real protection.
In practice: the complete sale file
Our standard for a smooth sale: up-to-date OIBT safety report, voluntary CECB for properties where energy will weigh in the discussion, asbestos survey for pre-1991 buildings, complete PPE (condominium) documents — all gathered before going to market, since every missing document extends the timeline at the worst possible moment. The notary checks the legal aspects; the valuation factors the documented condition into the price; and our selling guide sets out the full method. Technical terms are covered in the glossary.