Fundamentals

Condominium ownership: how private units and common property fit together

By Daniel Sardá · Published on July 11, 2026 · Updated on July 15, 2026

8 min read1,744 words

Condominium ownership combines exclusive rights over an individual unit with an inseparable interest in common areas and services. This guide explains its structure, documents, and basic rules.

At first glance, buying an apartment may look like buying a space enclosed by walls. But the transaction includes something more: an interest in the land, structure, stairways, roof, and other components without which that space could not function independently.

Condominium ownership is the legal arrangement that organizes this combination. It grants exclusive rights over an individual unit—an apartment, commercial space, or another independently usable area—while attaching to it an interest in common property. In Spanish-speaking jurisdictions, this arrangement is often known as propiedad horizontal. The word horizontal does not describe the physical orientation of the property; it refers to a way of allocating rights within a building or development.

This basic structure appears, in locally specific forms, in both Spanish legislation and the Argentine Civil and Commercial Code. The terminology, documents, governing bodies, and procedures, however, vary from one country to another.

Key idea: An owner does not possess only an undivided percentage of the building. The owner holds a defined unit together with an inseparable interest in the common property.

One right with two dimensions

Consider a residential building. Within an apartment, the owner may occupy, lease, or transfer the unit, subject to the applicable limits. At the same time, the owner shares with the other unit holders those elements that support or serve the property as a whole, such as the land, structure, access areas, and certain utility systems.

These two dimensions form a single ownership interest. The common interest passes with the unit when it is sold and generally cannot be separated and traded on its own. Nor does it identify a physical section of the lobby or roof that an owner may fence off and use as private property.

This inseparability distinguishes the arrangement from a mere collection of neighboring properties. Every unit depends on shared resources, and those resources require maintenance, funding, and decisions. The legal structure aims to define who controls each sphere and how matters affecting everyone are coordinated.

It is not the same as ordinary co-ownership

Under ordinary co-ownership, several people may hold shares in the same asset without each person necessarily having an exclusive unit. Condominium ownership, by contrast, begins with the combination of an individually defined unit and inseparable common property.

The distinction has practical consequences. An ordinary co-owner holds an undivided interest in the shared asset. The owner of a condominium apartment does not merely hold an undivided interest in the entire building: the owner has exclusive rights over the unit and an ownership share in the common property.

Nor should readers assume that condominium has precisely the same legal meaning in every country. Depending on the jurisdiction, a related term may serve as a colloquial equivalent or refer to a different legal form. Expressions such as homeowners' community, owners' association, consortium, common charges, or service charges also belong to particular national frameworks. Before applying a rule elsewhere, first identify the law from which it comes.

Condominium ownership is also different from communal property. Collective ownership lies at the center of the latter model; in the former, a defined private sphere coexists with common elements.

What is private, what is common, and who may use it

Looking at a space is not always enough to determine its legal status. Three relevant categories may exist within a building:

• Private elements: These form part of the unit over which its owner exercises exclusive rights.
• Common elements: These are jointly owned by the unit holders and serve the property's existence, safety, access, or operation.
• Common elements for exclusive use: These remain common property, but their use is reserved for one unit or certain owners when the law and the property's documents allow it.

An apartment is usually private, while stairways and the structure are usually common. Terraces, courtyards, roofs, balconies, and parking spaces tend to generate more confusion. A courtyard accessible only through one unit, for example, does not automatically become that owner's private property. It may remain common property designated for that unit's exclusive use.

The exact classification depends on the law, the instrument establishing the regime, the plans, and the governing rules. These sources may also allocate responsibilities separately: having exclusive use of a space does not necessarily mean owning it or bearing the full cost of every repair.

Practical caution: Ownership, use, and the duty to pay are separate questions. An answer to one does not automatically resolve the other two.

An ownership share is not a piece of the building

Each unit is generally assigned an ownership share, usually expressed as a percentage or coefficient. This is a legal measure, not a physical space. The holder of a 5 percent share, for example, does not receive five out of every hundred square meters of the hallway for individual use.

The share helps organize financial relations and, depending on the governing law and the issue at hand, may also affect collective decisions. It can provide a basis for allocating expenses, benefits, or liabilities. But it should not be assumed to determine every payment and every vote in exactly the same way. Statutes and governing documents may establish different criteria, exemptions, or voting thresholds.

Why should someone contribute to maintaining an elevator they rarely use? Because the charge does not always pay for individual consumption. It may also sustain the availability of the service, preserve the property as a whole, and maintain shared conditions of access and value. Both Spanish and Argentine law provide for duties to contribute to common expenses, although their rules and exceptions are not interchangeable.

The right question is not merely, “Did I use it?” but, “What obligation do the law, the title documents, and the governing rules assign to my unit?” This distinction prevents a reasonable intuition about consumption from turning into a mistaken legal conclusion.

Title documents and governing rules: the property's legal map

Two visually similar buildings can be organized differently. The instrument creating the ownership regime and its governing rules describe what physical observation cannot fully reveal: the units, percentages, permitted uses, common areas, and rules for administration and coexistence.

These documents define rights, but they do not operate in a vacuum. The law of each jurisdiction determines their required form, registration, permissible content, and limits. A rule is not necessarily valid simply because owners approved it or followed it for many years; it must comply with mandatory law and the relevant rights.

For a buyer, reading the governing documents is not a minor formality. They reveal burdens and restrictions that accompany the unit: its authorized use, the method for funding expenses, rules concerning alterations, and decision-making procedures. Clear documents reduce disputes and make the exercise of patrimonial rights more predictable.

From an institutional perspective, this arrangement shows that private property is not boundless power. It consists of defined and enforceable rights. When a decision made inside a unit affects the structure, safety, or rights of others, it is no longer a purely individual matter.

How shared resources are governed

The elevator must be serviced, the roof may need repairs, and the accounts have to be managed. No single owner can settle all these matters independently. Condominium ownership therefore requires collective procedures.

Depending on the country, an assembly, board, administrator, president, council, or other bodies may be involved. Spain regulates, among other bodies, the owners' assembly, president, and administrator. Argentina organizes the consortium, assembly, owners' council, and administrator. These examples illustrate the relevant functions; they are not a universal organizational chart.

An assembly turns individual preferences into decisions for the property as a whole. Its authority is not unlimited. Required majorities may vary with the subject, and collective action may be constrained by legislation, title documents, governing rules, and individual rights. It is not enough to say “the majority rules” without asking what the group was entitled to decide, through which procedure, and by what voting threshold.

An unavoidable tension appears here: each owner needs autonomy over an individual unit, while everyone depends on certain shared resources. A sound institutional framework does not eliminate that tension. It channels it through clear titles, predictable obligations, accessible information, and procedures that allow owners both to decide and to challenge decisions.

Key idea: Common governance is necessary because the owners are interdependent, but its legitimacy rests on defined powers and procedures—not simply on how many people support a measure.

Rights, duties, and common disputes

An owner may use and transfer a unit but must respect limits that protect the property, peaceful coexistence, and the rights of others. Owners also generally have duties related to maintaining and funding common elements. The precise scope of each right or obligation is jurisdiction-specific and may depend on the building's documents.

Disputes often expose a misunderstood boundary: work inside a unit that affects a common wall or utility system; an exclusively used courtyard whose repair no one wants to fund; a special assessment challenged because of its purpose or approval; or an activity that is lawful in the abstract but conflicts with the property's documented permitted use.

Before deciding who is right, it helps to organize the inquiry:

1. Identify the law currently in force in the country and, where relevant, local rules. 2. Review the title documents, governing rules, plans, and applicable property registration. 3. Confirm the element's classification, the unit's ownership share, and the resolution that gave rise to the decision or expense. 4. Determine which body decided, what procedure it followed, and what avenues of review are available.

This sequence does not replace legal advice in a specific dispute, but it helps frame the right question and avoid misleading equivalences borrowed from another country.

A private unit within a common structure

Condominium ownership makes it possible to divide the exclusive use of a property without pretending that its parts operate in isolation. Its logic becomes clear when two ideas are kept together: each owner controls a defined unit, and each unit carries an inseparable interest in the property that supports the whole.

The ownership share, common expenses, governing documents, and collective procedures all arise from this combination. None can be fully understood on its own. To know what was actually purchased—and which rights and obligations accompany it—it is not enough to look at the walls. The buyer must read the property's legal map in the applicable law, title documents, and governing rules.