Managing the roof terrace and water infiltration

What the roof terrace is and why it causes disputes

The lastrico solare is the flat roof covering that replaces a pitched roof and can be either common (accessible to all owners for equipment, antennas, drying racks) or granted for exclusive use to a single owner, typically the top floor owner who uses it as a private terrace. This double nature, a covering function serving the whole building but exclusive enjoyment reserved to one, explains why disputes arise so often: the exclusive user tends to treat it as purely private property, while structurally it keeps protecting every apartment below from water infiltration.

When waterproofing fails, or the membrane deteriorates over time, rainwater seeps into the layers below and shows up as damp patches, crumbling plaster, or outright leaks in the apartments underneath. At that point two distinct questions arise and must be kept separate: who must carry out and pay for repairing the roof terrace, and who compensates the damage already caused to the apartments below.

Article 1126 of the Civil Code: splitting repair costs

Article 1126 of the Italian Civil Code governs exactly this case, a roof terrace or level terrace under the exclusive use of one or more owners: the exclusive user contributes one third of the repair or reconstruction costs, while the remaining two thirds fall on all the owners of the building (or group of units) that the surface covers, in proportion to their ownership shares.

The logic is straightforward: the surface serves a double function, covering everyone (hence the community's two-thirds share) and providing exclusive enjoyment to one owner (hence that owner's additional one-third contribution, since heavier use, foot traffic, furniture, planters, can accelerate the waterproofing's wear). This split applies to extraordinary maintenance and reconstruction works. It does not apply to ordinary maintenance of the exclusive-use surface (cleaning, minor upkeep), which remains the exclusive user's own responsibility.

It is worth noting that the assembly cannot depart from this rule to the exclusive user's disadvantage without unanimous consent from everyone affected: a resolution that shifts the entire cost onto the exclusive owner, or excludes them entirely from contributing, can be challenged if it was not approved unanimously by the owners involved in the split.

Infiltration damage: who compensates the affected apartments

Separate from repair costs is compensation for damage already suffered, ruined plaster, damaged furniture, mold, in the apartments below. Here the general rules of civil liability apply, specifically article 2051 of the Civil Code on custodian liability: whoever has custody of the thing that caused the damage (the roof terrace) is liable, unless they prove an unforeseeable event.

In practice, when the surface is under exclusive use, Italian case law tends to identify concurrent liability between the exclusive user (de facto custodian of the surface) and the building's ownership community (which remains custodian of the structure in its shared covering function), typically in the same one third, two thirds proportion set by article 1126, unless a technical survey proves the cause is attributable exclusively to one party, for example an unauthorized private intervention that damaged the waterproofing, which would shift liability onto whoever carried it out.

For this reason the building should carry insurance covering infiltration damage and third-party liability: without coverage, splitting compensation between the exclusive user and the community becomes yet another source of dispute, on top of the one already open over repair costs.

Handling the claim: practical steps and documentation

As soon as an infiltration is reported, the property manager should follow a clear, documented path:

• Prompt inspection by a qualified technician (surveyor or engineer) to establish the actual source of the infiltration: not every damp patch comes from the roof terrace, some originate from plumbing or condensation, and assigning liability before a technical survey is a common mistake.
• Dated photographs of the damage, the roof surface, and any prior interventions, useful both for the survey and for any later dispute.
• Written, traceable communication to everyone involved (the exclusive user, the affected owner, the insurer if any) with clear deadlines for action.
• A repair estimate and an assembly resolution applying the article 1126 split, with the technical survey attached to the minutes.
• Opening a claim with the building's insurer, if the policy covers the case, and keeping all correspondence with the insurance loss adjuster.
• Filing all documentation, surveys, minutes, invoices, correspondence, in an organized and accessible way, useful even years later if the dispute reopens.

Frequently asked questions