Does GFA include voids?

No, voids are not included in the GFA.

Does GFA include car park space?

GFA does not include off-street parking but may include rooftop parking.

Does the Gross Floor Area include garages?

In some jurisdictions, garages that are in the basement area of a commercial building are included; otherwise, no.

Does Gross Floor Area include all floors in a building?

Yes, gross floor area includes all floors in a building.

GFA Explained: A Comprehensive Guide to Gross Floor Area

Gross Floor Area (GFA) is a term that defines the total amount of floor space in a building, measured from the outside face of the external walls. This guide looks at how to measure GFA, how it differs from other measurements, and how modern floor plan software can help with your calculations.

Blog, Floor Plans

By Tony Gillen Images by Celine Polden

What Is Gross Floor Area (GFA)?

Gross Floor Area (GFA) is generally defined as the total area of all floors inside a building measured from the outside face of the perimeter walls, excluding buttresses and other exterior protrusions. It includes all interior pillars, interior wall thicknesses, and common areas.

If it is a residential building, the Gross Floor Area usually includes roof decks, balconies, and patios when fully enclosed by a wall, surrounded by a solid railing higher than 42 inches (1.067m), or covered in some way.

Note that definitions of GFA- including which areas count towards it and which don’t - vary worldwide. Hence, you should check with local authorities or a professional appraiser to determine your location's most commonly used measurement standards.

Many countries are moving towards International Property Measurement Standards (IPMS), developed by more than 80 professionals and non-profit organizations, to document international property measurement standards. Other measurement standards include RICS (Royal Institution of Chartered Surveyors) and ANSI (American National Standards Institute).

How to Calculate Gross Floor Area

Gross Floor Area is essentially the total area of all the floors of a building, measured to the outside of the external walls. Here are a couple of ways to calculate GFA:

Option 1: Use an existing blueprint or floor plan

If you have an existing blueprint or floor plan for the building, you can import it into floor plan software like RoomSketcher. With RoomSketcher’s built-in area calculator, you can get your Gross Floor Area result in seconds - just click to exclude any uncovered or unenclosed external balconies or decks on the floor plan and then choose the “Gross Floor Area” calculation. See Calculate the Total Area of a Floor Plan for more information on RoomSketcher’s area calculations.

Option 2: Measure onsite

You can also measure up the property if you don’t have access to an existing floor plan.

Start with a walkaround - Walk around the property to get an idea of the shape.
Sketch the property on paper or tablet - Make a sketch of the property on paper or create a digital sketch using floor plan software on your tablet.
Find the rectangles - Now work on each floor. Note whether each floor is a simple rectangle or break it down into smaller rectangles (so you can multiply length x width for each rectangle and add them together).
Get the measurements - Measure each rectangle using a tape measure, roto wheel, or a laser to determine the size of each rectangle, factoring in internal and external wall widths.
Do the math - Multiply the length and width of each rectangle to calculate its size. Add together all the rectangular areas on the floor. Repeat for all floors, and sum the result to calculate the building’s total GFA.

Top RoomSketcher Tip
IPMS standards recommend reporting each floor individually, along with the total GFA for the building.

What is Included in Gross Floor Area?

Gross Floor Area generally includes everything inside a building. Examples of areas typically included in the GFA are:

All the floors in a multi-story building, unless your instructions are to measure only a specific area or part of the building.
Atriums and lobbies -but only count the floor level in the calculation - do not include any open areas above.
Interior walls - GFA includes the thickness of interior walls, pillars, etc.
Internal corridors.
The footprints of stairways, elevator/lift shafts, and vertical duct shafts on each floor through which they pass.
Basements that are usable and have reasonable ingress and egress.
Common areas, such as restrooms, breakrooms, clubhouses, meeting rooms, mechanical equipment areas, storage rooms, and laundry rooms.
Unheated and uncooled areas of industrial buildings, since occupants may use them.
Rooftop terraces and parking spaces, even if uncovered.
In residential buildings, include balconies, decks, and patios if they are wholly surrounded by a wall or fence greater than or equal to 42 inches (1.067m). If they are not walled or fenced, you may include covered areas. Count the area only to the drip line (an imaginary line extending down from the edge of a roof, balcony, or walkway immediately above).

Top RoomSketcher Tip
Because standards vary slightly worldwide, check with your local authorities for a complete list of the standard inclusions in your area.

Gross Floor Area Exclusions

Here are examples of areas to exclude from GFA measurements:

Driveways and walkways.
Exterior and separate parking areas.
Balconies, decks, and patios in a commercial building.
In residential buildings, exclude uncovered portions of balconies, decks, and patios that are not surrounded by a wall or fence of the approved height.
Enclosed ductwork and crawlspaces.
Exterior loading bays and docks.

GFA Compared: How It Differs from Other Measurement Standards

Let's take a look at the differences between Gross Floor Area (GFA) and other calculations. For additional information on measurement standards, see GIA Explained, The Ultimate Guide to Understanding Property Size, and What is Gross Living Area, and How do you Calculate it?

Gross Floor Area VS. Gross Internal Area (GIA)

Gross Internal area is the total internal floor space of a building, measured from the inside face of the external walls. In contrast, Gross Floor Area is measured from the outside face of the exterior walls.

Gross Floor Area VS. Net Internal Area (NIA)

The Net Internal Area is the total internal floor space of a building that is for building tenants' exclusive use and thus excludes common areas such as shared lobbies, maintenance rooms, and restrooms. In contrast, Gross Floor Area generally includes all the space inside a building.

What Is the Difference Between GFA and GLA?

While GFA generally includes everything inside a commercial or residential building, Gross Living Area (GLA) is focused on finished living space and is used for residential buildings only. In addition, GLA includes above-ground areas, while GFA may include below-ground areas.

Gross Floor Area VS. Total Living Area (TLA)

While Gross Floor Area generally includes everything inside a commercial or residential building, Total Living Area describes the total finished, heated, livable space on a residential property, including finished basements, attics, and adjacent, unconnected buildings.

Frequently Asked Questions (FAQ)

Make your GFA Measurement and Reporting Easier

You can calculate a building's GFA by measuring each floor or by using floor plan software, like RoomSketcher, to simplify the process.

Even more, RoomSketcher allows you to transform your hand-drawn sketches into professional floor plans. If you have any questions or want to discuss our services, please contact us. We would be happy to help you.

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