Flat roof in exclusive use: the one-third, two-thirds calculation

The Article 1126 rule

Article 1126 states that, when the use of the flat roof or part of it is not common to all owners, whoever has its exclusive use must contribute one-third of the expense for repairs or reconstruction of the roof. The other two-thirds fall on all the owners of the building, or of the part of it for which the roof serves as covering, in proportion to the value of each one's floor or portion of floor.

The rationale is clear: the holder of the exclusive use draws an additional private benefit from the roof, as if it were a terrace, and therefore bears the one-third share. The units below, by contrast, benefit from the covering and protection from the elements, and therefore take on the two-thirds.

The same approach is applied by case law to level terraces that serve as covering, when their use is exclusive to one owner.

Step-by-step numerical example

Suppose a waterproofing renewal expense of 9,000 euro. The roof is in the exclusive use of the top-floor owner and serves as covering for three units below.

First step: the one-third share, that is 3,000 euro, falls on the holder of the exclusive use. This part disregards the thousandths and derives directly from the fraction set by the rule.

Second step: the remaining two-thirds, that is 6,000 euro, are shared among the owners served by the roof in proportion to the value of their floor. If the three covered units have, in the served portion, values of 500, 300 and 200 thousandths, the shares are 6,000 times 0.500 equals 3,000 euro, then 1,800 euro and finally 1,200 euro. The sum of the shares, 3,000 plus 3,000 plus 1,800 plus 1,200, comes back to 9,000 euro.

• Exclusive-use holder: one-third of 9,000 equals 3,000 euro
• Unit covered with 500 thousandths: two-thirds times 0.500 equals 3,000 euro
• Unit covered with 300 thousandths: 1,800 euro
• Unit covered with 200 thousandths: 1,200 euro

When it applies and when it does not

The thirds rule applies to expenses for repair and reconstruction of the roof as a covering structure, not to works concerning only the flooring or elements at the exclusive service of the holder, which remain entirely their burden.

If instead the roof is common to all owners, with no exclusive use, Article 1126 does not apply and one reverts to the general thousandths criterion of Article 1123. Distinguishing between a common roof and a roof in exclusive use is therefore the first thing to establish before setting up the split.

Another delicate point concerns damage from infiltration coming from the roof: liability and the related compensation follow their own rules and do not automatically coincide with the sharing of repair expenses under Article 1126, which governs the cost of the maintenance work and not the duty to compensate.

Managing the split in the financial report

For correct management the manager must precisely identify the units served by the roof and their proportional values, keep the holder's one-third share separate, and attach to the report the detail of the calculation, so that each owner can verify their position.

The risk of error grows in buildings with several roofs, level terraces and different served portions, where each job concerns a different set of units. In these cases a dedicated table for each covering avoids assigning shares to those not served.

A management software such as AmministraPro lets you create a specific table for the roof, reserve the one-third share to the exclusive-use holder, and automatically share the two-thirds among the covered units by floor value, producing a transparent report. The features are described on the features page and the plans on the pricing page.

Frequently asked questions