A cellar refers to a room located in the basement or lower ground floor of a building, primarily intended for storage. In a co-ownership, its legal status directly determines the owner’s rights over this space, the authorized works, and the obligations that arise from it.
Private part or common part: the legal status of the cellar in co-ownership
Confusion is common. A cellar attached to an apartment is not automatically a private part in the sense of the co-ownership regulations. Three configurations coexist depending on the buildings.
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The most common: the cellar is listed as a private lot in the descriptive state of division. The co-owner has free disposal of it, within the limits of the regulations. They are responsible for its maintenance and any works at their own expense.
Second case: the cellar is a common part for private use. The co-owner can use it, but the structure (walls, floor, ceiling) remains collective property. Any structural modification then requires a vote at the general assembly. This is a point that many owners discover when they start works.
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Third case, rarer: some cellars house collective installations (meters, main pipelines, technical room) and thus fall under common parts. No co-owner can claim exclusive use of it.
To know the exact status of a cellar, the only reliable source remains the co-ownership regulations and the descriptive state of division. The property manager can provide these documents. A comprehensive guide on cellar definition and utility allows for a deeper understanding of the distinctions between these three regimes.
Use and storage in the cellar: what the co-ownership regulations really allow
The co-ownership regulations set the limits of use, and they vary significantly from one building to another. Even in a private lot, the owner does not have free rein.
Storage of materials and products
Most regulations prohibit or strictly limit the storage of flammable liquids and gas bottles in cellars. The tolerated quantities remain low, even zero in some buildings. Food items pose fewer regulatory issues, but the humidity and ventilation of the cellar condition their preservation.
Installing a freezer or electrical appliance in a private cellar is generally possible, provided that the electrical installation complies and that the regulations do not explicitly prohibit it.
Restrictions related to the building’s purpose
- A commercial use (storage of goods for resale, workshop) may be prohibited by an exclusive bourgeois destination clause, common in residential co-ownerships.
- The separate rental of the cellar, as an independent lot or storage space for a third party, sometimes requires authorization from the general assembly depending on the wording of the regulations.
- Using a cellar for furnished tourist rental raises additional constraints, particularly regarding change of use and compliance with habitability standards.
Transforming a cellar into living space: urban planning formalities and tax obligations
Converting a cellar into a living room is increasingly appealing to owners, especially to gain space in densely populated urban areas. The process involves several regulatory steps that many underestimate.
Preliminary declaration or building permit
As soon as a project creates living space from a basement, urban planning authorization is required. The nature of this authorization depends on the created area and the applicable local urban plan. A preliminary work declaration is sufficient in some cases, but a building permit may be required beyond a certain threshold or in protected areas.
In co-ownership, this transformation also requires a vote at the general assembly if it affects the common parts or modifies the external appearance of the building.
Tax declaration after completion
Works creating living space must be declared to the tax authorities within 90 days of their completion. This declaration leads to a reassessment of the property’s rental value, and thus an increase in property tax. Forgetting this exposes one to a reassessment.
Thermal insulation and summer comfort: the cellar facing new requirements
Fitting out a cellar as a living space is not limited to laying flooring and installing electricity. Thermal insulation has become a regulatory issue in its own right.
When the layout is part of a broader renovation of the building (facade renovation, roofing work), certain insulation works become mandatory. There are cases of exemption, but they are still regulated and require technical or economic justification.
A less often discussed angle concerns summer comfort. Cellars, naturally cooler than upper floors, present a real thermal advantage during periods of high heat. This characteristic partly explains the growing interest in transforming cellars into living spaces, beyond just gaining surface area.
Ventilation remains the critical point. Without an appropriate air renewal system, the ambient humidity of a basement quickly degrades living conditions and promotes mold. A prior diagnosis of the existing humidity and ventilation conditions is essential for the project’s viability.
Works in co-ownership cellar: who pays and who decides
The distribution of costs directly depends on the status of the cellar. In a private lot, the co-owner alone bears the costs of maintenance and repair of the interior (painting, flooring, electrical installation).
- Works affecting the structure (load-bearing walls, slabs, waterproofing) fall under common charges, even if the cellar is private, as the structure belongs to the co-ownership.
- Water damage from a common pipeline that damages a private cellar engages the responsibility of the co-owners’ union.
- Improvement works voted at the assembly (installation of lighting in cellar corridors, securing access) are distributed according to the shares defined in the regulations.
The property manager plays a central role in coordinating these interventions. Every co-owner must allow access to their cellar for works affecting the common parts, even without their individual consent, as long as the assembly has voted on the resolution.
The legal status of the cellar conditions every decision, from simple storage to transformation into living space. Checking the co-ownership regulations before any project remains the most protective reflex, including to anticipate the tax consequences of a layout.