Gross Building Area

From basic definitions to measurement methods, through to their importance in valuing a property, this comprehensive guide unveils all aspects of the 'Gross Construction Area' (GBA) . With practical examples, a frequently asked questions section and tips to avoid common mistakes, this article serves as a complete manual to understand the meaning and importance of the Gross Construction Area in a property.

The Gross Building Area (GCA) is more than a simple number; It is an essential metric that affects different aspects of a property. This concept is crucial for a series of processes, from evaluating a property to its sale or rental potential. In this article, we will delve deeper into the concept of Gross Building Area, exploring what it is, how it is calculated and its importance in the real estate sector.

Definition of Gross Building Area

The Gross Building Area (GBA) is the sum (m2) of the gross areas of all floors , of all floors of a property (above and below the threshold level), as long as they comply with the regulatory ceiling height, measured by exterior perimeter and axes of walls or other separating elements of the building or fraction.

When calculating the Gross Building Area:

Included are:

  • interior and exterior walls (these, measured by the axes of the walls or other separating elements of the building or fraction);
  • private covered balconies (open or closed);
  • steps;
  • covered terraces and porches;
  • elevator shafts;
  • rooms (bedrooms and living rooms);
  • kitchens and pantries;
  • vestibules and interior circulations;
  • sanitary facilities;
  • private basements and attics (with use identical to that of the building or fraction and to which coefficient 1 applies);
  • storage rooms, storage or other compartments with a similar function;
  • garages;
  • independent attachments;

The following are excluded:

  • areasbuilt below the threshold level, if they are intended exclusively for parking;
  • areas intended for basement storage, without regulatory ceiling height (below 2.40 m);
  • attics without regulatory height (below 2.40 m);
  • technical areas above or below ground (PT, thermal power plant, swimming pool technical area, waste collection compartments, etc.);
  • uncovered terraces;
  • uncovered balconies and porches;
  • public outdoor galleries;
  • streets;
  • spaces free for public use and covered by the building (entrance halls, stairs, landings, etc.);

This value is crucial in determining the market value of a property and is an essential metric for any real estate transaction.

How to calculate the Gross Building Area

Gross Construction Area, how is it calculated?

Gross Building Area = Gross Private Area + Gross Dependent Area

Example: If an apartment has 100 m² of Gross Private Area and 20 m² of balcony (dependent area), its GBA will be 120 m².

How to measure Gross Building Area

GCA measurement can be done in several ways, and each one has its advantages and disadvantages:

  • Traditional Methods : Tape Measure. This is the most basic and accessible method, but it can be time-consuming and less accurate.
  • Technological Methods : Laser Equipment. These devices offer more accurate measurement and are ideal for large spaces.
  • Official Documentation : Property Plans. Architectural plans are the most accurate and reliable way to determine GBA.

Gross Building Area measurement rules

The gross areas occupied by the fractions must be delimited as follows:

  1. by the outer contour of the building's exterior walls, excluding columns, pillars or other elements detached from the face of the wall;
  2. by the outer contour of the walls that separate the units from the common spaces;
  3. along the axis of the walls that separate differentfractions.

When measuring the gross area it must be:

  1. INCLUDED the entire surface occupied by:
    • indoor spaces;
    • balconies and loggias;
    • covered and paved outdoor spaces (e.g., carport, parking area under the building, circulation gallery);
  2. INCLUDED half of the surface occupied by:
    • usable outdoor spaces that constitute coverage of other spaces (e.g., visitable terrace, roof garden);
    • covered but unpaved outdoor spaces (e.g., garden under building);
  3. EXCLUDED the surface occupied by:
    • spaces that are not accessible or not usable (e.g., non-accessible basement, attic, non-visitable terrace);
    • spaces with ceiling heights of less than 1.80 m (e.g., technical floor);
    • unenclosed spaces with floors laid directly on the ground (e.g., sidewalks, pedestrian paths, access to garages);
    • spaces that are not covered or paved (e.g., backyard, garden);
    • spaces in the public domain (e.g., road traffic under the building).

It is also observed that:

  • stairs, ramps, elevator shafts and plumbing ducts must be included in the gross area of each floor;
  • stairs, ramps and other inclined spaces are accounted for in their horizontal projection;
  • in double-height spaces, the area must only be counted once;
  • in adjacent buildings with common walls, the delimitation of buildings must be done along the axis of these walls4 (e.g., buildings resulting from the division of a building into two);
  • in adjacent buildings where one of them abuts another without the construction of an enclosing wall, the delimitation of the added building must be done by the exterior face of the wall of the existing building.

The gross area must be expressed in square meters.

The Importance of Gross Building Area

The Importance of Gross Construction Area in the value of a property

Understanding the Gross Building Area and its implications is essential for real estate professionals, builders, investors, and also for property buyers and sellers.

  • Property Value : GBA is one of the factors that most influence the value of a property. Normally, the larger the built area, the higher the value of the property. This is particularly relevant for clients in the upper-middle and luxury segment, who value properties with larger built areas.
  • Urban Planning and Licensing: GBA is a crucial factor in urban planning and the construction licensing process. Determines the maximum size that a building can have on a given lot, influencing the urban design and population density of an area.
  • Design and Architecture: GBA influences the architectural design of a building. Architects must consider GBA when designing a building to ensure space is optimized and complies with local codes. On the other hand, the built area is a distinguishing factor in the luxury market, which favors social spaces and large suites.
  • Energy Efficiency and Sustainability: GBA can also have an impact on the energy efficiency of a building. Larger buildings may require more energy for heating, cooling and maintenance, affecting thermal comfort planning, as well as the sustainability and operational costs of the property.
  • Tax Implications: The built area of a property affects its tax assessment. Properties with higher GBA may have higher taxes, such as the Municipal Property Tax (IMI) in Portugal.
  • Legislation and Regulations: Being aware of the GBA of your property can help you avoid legal problems in the future. This is not the first time that I have failed to close a deal due to non-conformities between real areas and areas registered in official documents. Especially in the case of foreign buyers, who are normally well advised from a legal point of view.

Common Mistakes and How to Avoid Them

Measuring GBA can be a complicated process and it is easy to make mistakes.

Always confirm the Gross Construction Area in official documents to avoid unpleasant surprises

  • Confusion between Gross Area and Useful Area :
    • Error: GBA is often confused with the usable area, which is the truly habitable space. While GBA includes the entire built space, including walls, balconies, etc., useful area refers only to the internal habitable space.
    • How to avoid: Always clarify the difference between these two measurements in your descriptions and in communication with customers. The lack of transparency does not help in the marketing of a property.
  • Lack of Verification :
    • Error: Sometimes there are inconsistencies in the areas registered in the various official documents related to the property (Land Booklet, Permanent Land Registry Certificate, etc.).
    • How to avoid it: If you are considering selling your home, check all the necessary documents first. If you identify significant differences, you should contact the relevant public services, such as the City Council, the Tax Authority and the Land Registry Office, to align and update this information. Do not leave surprises of this type until the final moment of the transaction, as trust is an essential factor in the process of selling a property.
  • Inattention to Changes and Expansions:
    • Error: Not registering with the various official bodies changes or extensions to a property that affect its GBA. I have already lost millions of deals because of this error.
    • How to avoid: It is not enough for the renovations planned by the architect / builder to be registered with the respective City Council.All documents associated with the property will have to be updated with the respective official bodies.
  • Errors in marketing and promoting the property:
    • Error: Not using GBA when promoting the sale of a property, using only the useful area.
    • How to avoid: Highlight GBA in your marketing strategies, showing how it adds value to the property. The property is valued as a whole, the living area but also the area of the walls, as they represent a cost and contribute to the real and taxable value of the property.

Frequently Asked Questions about Gross Building Area

Frequently Asked Questions about Gross Building Area

These are some of the most frequently asked questions about the Gross Building Area of a property:

1. What is, and how is the Gross Building Area (GBA) calculated?

The Gross Building Area (GBA) is the value in square meters (m²), obtained by summing the areas of all floors, both above and below ground, measured from the outside of the exterior walls or by the axes of the separating walls of real estate.
Included are: private balconies, accessory areas and the corresponding share in the building's common circulation.
Excluded are: non-habitable attics; areas intended for parking; technical spaces (such as PT, thermal power plant, waste collection compartments, etc.); terraces, balconies and uncovered porches; as well as exterior galleries, streets and other free spaces for public use covered by the building.

Gross Area ofConstruction = Gross Private Area + Gross Dependent Areas

2. What counts for the Gross Building Area?

The interior and exterior walls (these, measured by the axes of the walls or other separating elements of the building or fraction); steps; porches; elevator boxes; rooms (bedrooms and living rooms); kitchens and pantries; vestibules and interior circulations; sanitary facilities; private basements and attics (with use identical to that of the building or fraction and to which coefficient 1 applies); private covered balconies (open or closed); terraces; collections; storage or other compartments with a similar function; garages; independent attachments; the share of what corresponds to it in the common circulation of the building

3. Where can I check the Gross Building Area of a property?

Information on Gross Building Area can be found at:

  • Property Booklet - available in the reserved area of the property owner(s), on the Tax Authority website.
  • Land Registry Certificate - Which can be requested at a Land Registry Office, a Citizen's Store or a Registry Office.
  • In the Housing Technical Data Sheet - This must be delivered when the property is signed for Purchase and Sale Deed or a duplicate can be requested from the property developer or municipal services.
  • In the Architectural Plans - Which should have been given to you when purchasing the property.

4. Why is it important to know the Gross Building Area of a property?

Knowing the Gross Building Area (GBA) is essential to assess the value of a property and compare it with other properties on the market. Furthermore, GBA is one of the criteria used in calculating the tax asset value (VPT) of a property, which directly influences the value of the Municipal Property Tax (IMI) and the Property Transfer Tax (IMT).

The Tax Asset Value (VPT) is calculated using the following formula: VPT = Vc x A x Ca x Cl x Cq x Cv

Caption: Vc: Base value of the buildings constructed; A: Gross Building Area plus the area exceeding the implementation area; Ca: Allocation coefficient; Cl: Location coefficient; Cq: quality and comfort coefficient; Cv: aging coefficient.

5. How can I correct the Gross Building Area of my property, if it is wrong?

If the Gross Building Area of your property is wrong, you must hire a specialized technician (architect or engineer) to carry out the correct measurement and prepare a plan of the property with the updated GBA. You must then present this documentation to the Land Registry Office and the City Council to update the records and, if applicable, to the Tax and Customs Authority to correct the tax asset value (VPT) and, consequently, the Municipal Property Tax (IMI) and the Property Transfer Tax (IMT). Be careful, because if these are profound changes that include new spaces in the property, built afterwards, you will first have to submit a change project to the City Council.

6. I have urban land, how do I calculate its maximum Gross Building Area?

The construction capacity of an urban land can be calculated as follows: Maximum GBA = Land Area x Use Index. For example, for a plot of land with an area of 2,000 m² and a Use Index of "0.4", it will be possible to build, at most, a house with 800 m² of Gross Building Area.

The " Use Index" or " Maximum Construction Index" can be consulted at:

  • In the Subdivision Plan , if the land is part of a subdivision;
  • If provided for in the Municipal Master Plan (PDM), according to the classification of the land within the scope of territorial planning.
  • By submitting a PIP - Request for Prior Information to the respective City Council, which consists of a request for information about the feasibility of carrying out a certain construction, on a certain piece of land.

7. What are the differences between Gross Building Area, Gross Private Area, Useful Area and Dependent Area?

  • Gross Building Area: Refers to the total area of a building, including all its parts, such as exterior walls and common spaces. It therefore covers the sum of all gross private areas and dependent areas.
  • Useful Area: It is equal to the sum of the areas of all compartments in the house, including lobbies, interior circulations, sanitary installations, storage, other compartments with a similar function and wall cupboards, and is measured by the interior perimeter of the walls that limit the fire , discounting gaps of up to 30 cm, interior walls, partitions and ducts. Excludes common areas of the building.
  • Private Gross Area: It is similar to the Useful Area and is sometimes confused, but it includes closed balconies and terraces, cellars and attics for exclusive and private use.It is the effectively usable space, where you can furnish and live.
  • Dependent Area: Dependent areas are the parts of a property that are accessory and are not included in the private gross area . Typically, it includes spaces intended for parking, storage, terraces, balconies, service areas and other areas that are not considered as the main living area , as they serve secondary or support purposes.

Related articles

Área Bruta Privativa
It corresponds to the total surface, measured by the outer perimeter and axes of the walls or other separating elements of the building or fraction.
Área Bruta
It is the total surface of the building or fraction, and represents the sum of the gross areas of all floors of a building, above and below ground, and is measured considering the exterior of the walls that delimit or separate the dwellings.
Área do Terreno Livre
The free land area corresponds to land not occupied by buildings (outdoor spaces) and includes gardens, parks, playgrounds, swimming pools, backyards and other areas.

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