Practical guide
Handling water infiltration damage between units
Water infiltration between one apartment and the unit below is one of the most common disputes in shared residential buildings. The first question is not how much the repair costs, but where the water is coming from: if the cause lies in a private system or structure, the responsible owner pays; if it involves a common part such as a shared drainage pipe or a roof terrace, cost allocation follows civil code rules for shared property. This guide explains how to identify the cause through a technical survey, how liability splits between private property and common parts, what role insurance plays, and how the property manager should handle the whole case, documentation included.
First step: identifying the cause through a technical survey
Before discussing who pays, you need to know where the water is coming from. A leak can originate from a private plumbing system (internal pipes, fixtures, a washing machine), from an exclusively owned element such as a private terrace, or from a common part such as the vertical drainage stack, the roof, or a roof terrace serving several units.
Once notified, the property manager must act quickly to have the origin of the damage assessed, typically by a technician or plumber who inspects the systems and structures involved. A written survey with photographs and a precise indication of the infiltration point is what prevents later disputes among owners and allows liability to be established correctly.
Until the cause is confirmed, it is still worth documenting the damage suffered by the affected apartment, such as photographs, the date of the first report, and any urgent action taken to limit the damage, since these elements matter both in insurance negotiations and in any subsequent dispute.
Common parts or exclusive property: who is liable
If the infiltration originates from a common part, article 1117 of the Italian civil code lists the roof, roof terraces, and main drainage pipes among shared elements: damage caused by these is allocated among all owners according to their ownership shares, except for a roof terrace or terrace under exclusive use, where article 1126 sets out a different allocation between the owner who uses it exclusively and the other owners who still benefit from it as a covering.
If the leak instead originates from a system or structure under exclusive ownership, for example an internal bathroom pipe or a private terrace not classified as a shared roof covering, liability falls on the owner of that unit, who is responsible both for damage to their own apartment and for damage caused to the unit below.
The property manager does not decide a disputed allocation alone: they gather the technical survey, bring it to the attention of the assembly or the owners involved and, if needed, seek legal advice before proceeding with charges that could later be challenged.
The role of insurance
Many building liability policies cover damage caused to third parties by common parts, while individual homeowners' policies typically cover water damage originating from the insured apartment. In practice, when the cause is not yet clear, both the building's insurer and the insurer of the owner suspected of causing the damage may become involved, comparing notes based on the survey to determine who settles the claim.
It is good practice for the property manager to notify the building's insurer promptly as soon as a common part is suspected to be involved, attaching photographs and the survey as soon as it is available: policy reporting deadlines are often tight, and a delay can jeopardize coverage.
If liability falls on an owner because of a private system, that owner is the one who must activate their own home insurance policy, if they have one: the property manager can flag the situation but does not step in to manage another owner's personal claim.
Cost allocation and practical management by the property manager
Once the cause is established, the property manager prepares the allocation consistent with the survey findings: if the damage comes from common parts, the cost of structural repair is entered in the building's financial statement and split according to ownership shares, while any compensation for damage suffered by the unit below follows the insurer's determination or an agreement between the parties.
If liability rests with a single owner, fixing the cause and compensating the neighbor for the damage remain that owner's responsibility, and the assembly is not required to approve a shared expense for that part, except for any related work on connected common parts, for instance replacing a section of a shared drainage stack.
Orderly handling of reports, surveys, insurance communications, and cost allocations helps close the case without disputes. Management software such as AmministraPro lets you track the initial report, attach the survey and photographs, log communications with insurers, and generate the correct allocation directly in the financial statement, keeping documentation from scattering across emails and reducing errors in splitting costs among the owners involved.
Frequently asked questions
Who pays for infiltration damage if the cause is the shared drainage stack?
If the leak originates from the vertical drainage stack, which article 1117 of the Italian civil code classifies as a common part, the repair cost and resulting damage are allocated among all owners based on their ownership shares. The property manager includes the expense in the building's financial statement like any other common part maintenance, after having the cause confirmed by a technical survey.
Does the owner upstairs always have to pay for damage to the unit below?
Only if the infiltration originates from a system or structure under their exclusive ownership, such as an internal pipe or a fixture. If the cause is instead a common part, for example the roof or a shared drainage stack, the upstairs owner is not personally liable and the cost follows the ownership share allocation set for common parts, unless the damage was made worse by proven negligence on their part.
What happens if the roof terrace is under one owner's exclusive use?
Article 1126 of the Italian civil code sets a specific allocation for a roof terrace or terrace under exclusive use: the owner with exclusive use contributes alongside the other owners who still benefit from it as a covering, in a different proportion from the ordinary allocation. This is a case where the technical survey needs to clarify precisely whether the damage actually originates from that surface.
How quickly must the property manager act after an infiltration is reported?
There is no single statutory deadline, but the property manager must act promptly, both to limit the damage from worsening and because insurance policies often impose tight reporting deadlines. Good practice is to have a technician or plumber inspect the situation as soon as the report is received and to document every stage, so there is solid evidence in case of disagreement among the owners involved.
Is a technical survey always necessary even for minor damage?
Even for limited damage, a written technical assessment is advisable, because it clearly establishes the origin of the water and protects both the property manager and the owners involved from later disputes. Software such as AmministraPro lets you attach the survey and photographs directly to the case, so the documentation stays available for the assembly, the insurer, or any subsequent assessment.
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