Land and Subsoil of a Condominium: Ownership and Decisions

The land on which the building stands is the first common part listed by Article 1117 of the Italian Civil Code: it belongs to all owners in proportion to their thousandths (millesimi), unless a title states otherwise. The subsoil, meaning the area below that is not occupied by the foundations, follows the same fate through Articles 840 and 1117 of the Civil Code. No single owner may therefore excavate in depth to create exclusive spaces without the consent of the others: doing so would appropriate a common asset.

What the land means

The condominium land is the portion of terrain on which the whole building rests, together with the part immediately below where the foundations are set and the surface supporting the ground floor pavement. This is not a cadastral detail: it is the physical element carrying the entire construction, which is why the law places it among the assets necessary for common use. The footprint of the building on the ground falls within this notion too.

Common ownership of the land explains why rebuilding after a collapse, or works affecting the base of the construction, concern the community of owners and not the ground-floor owner. Whoever owns the lowest apartment does not become owner of the land simply because they are closer to it.

The subsoil and the default rule

The subsoil is the space existing in depth below the area occupied by the building and not intended for any particular use. In the absence of a title attributing exclusive ownership to one owner, that space is common. The reason is twofold: Article 840 extends ownership of the land to the column beneath, while Article 1117 lists the land among the common parts. Combining the two rules, the underground volume belongs to the community.

This has an important practical consequence: if an owner, perhaps the holder of a cellar or a garage, excavates to lower the floor level or create a basement room, they are drawing on a common asset. The operation requires the consent of the other co-owners and cannot be decided unilaterally.

Excavations, cellars and underground extensions

Appropriation of the subsoil by a single owner amounts to a genuine removal of the common asset. In such cases the administrator may act with the action for reinstatement of possession to restore the state of the premises, and may also claim damages. De facto availability is not enough: without a written title or a matured acquisition by adverse possession within the terms of the law, the space remains everyone's.

• Lowering a cellar floor by digging into the common subsoil requires the consent of the other owners
• Building a basement room under exclusive property still affects the shared volume underneath
• More intensive use of a common asset is allowed only if it does not alter its purpose and does not prevent equal use by others, under Article 1102
• Modifying the foundations or the supporting terrain affects building stability and must be assessed with particular technical caution

When the subsoil is exclusive property

The presumption of common ownership is rebuttable: it yields to contrary proof. Whoever claims exclusive ownership of the subsoil, or a portion of it, must produce a suitable title. This may be the original purchase deed reserving that volume to a specific unit, a condominium regulation of contractual nature accepted by all, or an acquisition by adverse possession proven in court. Without one of these elements, the claim does not stand.

It is worth remembering that a mere cadastral entry does not equal a title of ownership: the cadastre serves tax purposes and is not proof of title. To establish who owns what, one must trace the deeds of provenance and the regulation.

Cost allocation and meeting decisions

Being common assets, the conservation costs and works concerning land and subsoil are shared among owners on the basis of ownership thousandths, under Article 1123 of the Civil Code, unless different criteria are lawfully provided. Works exceeding ordinary administration, such as foundation consolidation, must be resolved by the owners' meeting with the required majorities. The administrator has the duty to preserve the common parts and may order urgent works to protect stability, then reporting to the meeting.

Keeping track of the ownership of common parts, the thousandths and the history of structural works is easier with management software that centralizes documents, tables and resolutions. With AmministraPro the administrator finds the deeds and expenses of each condominium in a single digital archive, with automatic allocation on the correct thousandths. The features are described on the /funzioni page and the plans, with transparent costs, on the /prezzi page.