Understanding Floor Area Ratio for Condominiums: Essential Knowledge That Affects Real Estate Value

“This property has room in its floor area ratio, so its future value is less likely to decline.”

“What is floor area ratio? Why does it affect property value?”

Have you ever wondered about these questions?

In fact, many condominium buyers enter into contracts without understanding this important indicator. Floor area ratio (FAR) is a numerical value that shows the ratio of total floor area to the site area, and it is an important criterion that affects the possibility of future rebuilding and living environment comfort.

This article will explain in easy-to-understand terms everything from basic knowledge about floor area ratio when choosing a condominium to checkpoints for determining property value.

What is Condominium Floor Area Ratio? A Basic Indicator of Real Estate Value for Beginners

Floor area ratio is a numerical value that indicates the maximum ratio of buildable floor area to the site area. This indicator is often overlooked when purchasing a condominium, but it is an important element that affects the property’s value and living environment.

The reason why floor area ratio is important is that it directly relates to the essential value of the property, such as the residential density of the condominium, the height of the building, and the possibility of future rebuilding.

Basic Understanding of Floor Area Ratio

Floor area ratio is calculated using the following formula:

Floor area ratio (%) = (Total floor area ÷ Site area) × 100

Example:

• Floor area ratio of 200%: The total floor area can be up to 2 times the site area
• For a 100㎡ site, a building with a total floor area of up to 200㎡ can be constructed

This value is determined by urban planning according to each area, and different values are set according to the characteristics of the region.

Area Characteristics	Typical Floor Area Ratio	Features
Quiet residential areas	100-200%	Mainly low to mid-rise buildings
Residential areas	200-300%	Many mid-rise condominiums
Around stations	300-500%	High-rise condominiums possible
City centers	500-1000%+	Super high-rise buildings can be built

Real Estate Experts Explain! The Meaning and Importance of Floor Area Ratio in Real Estate Selection

According to real estate appraisers, “floor area ratio is not just a number, but an important indicator that determines the limit of land use.” Floor area ratio is a legal regulation stipulated in the Building Standards Act, and buildings that exceed this value cannot be constructed.

Three reasons why floor area ratio is important in real estate selection

1. Directly related to living environment comfort
2. Low floor area ratio → Lower building density → Better sunlight & ventilation
3. High floor area ratio → Higher building density → Exchanged for urban convenience
4. Affects future asset value
5. Room in floor area ratio → More likely to maintain value in future rebuilding
6. At maximum floor area ratio → May be difficult to rebuild at the same scale
7. Indicates stability of the surrounding environment
8. Floor area ratio is part of urban planning → Reflects the future vision for the area
9. Regulation to protect the living environment in the long term

[Comparative Example] High vs. Low Floor Area Ratio Condominiums

Features	High Floor Area Ratio (400%+)	Low Floor Area Ratio (200% or less)
Location	City centers & near stations, excellent convenience	Common in residential areas & suburbs
Building	High-rise, good views	Low to mid-rise, less oppressive feeling
Environment	Concentrated buildings, urban atmosphere	More green space & room
Suited for	Those who prioritize convenience	Those who prioritize quiet environment

Floor area ratio is not just a number but an important indicator of the “density feeling” of a condominium. It is an important factor in choosing a living environment that matches your lifestyle and values. When viewing actual properties, check the floor area ratio along with the surrounding environment.

[Easy Explanation with Diagrams] How to Calculate and Interpret Condominium Floor Area Ratio

The method of calculating floor area ratio is very simple. It is calculated by finding the ratio of the building’s total floor area to the site area. It is important to understand this calculation method and interpretation when considering a condominium purchase.

Basic Floor Area Ratio Formula—How Much Area Can Be Built on 100㎡ of Land?

The formula for calculating floor area ratio is very simple:

Floor area ratio (%) = (Total floor area ÷ Site area) × 100

Concrete Example

• For a site area of 100㎡ with a floor area ratio of 200%
• 100㎡ × 200% = 200㎡ is the maximum buildable floor area
• This means a building with a total of 200㎡ can be built, such as 50㎡ on the 1st floor, 50㎡ on the 2nd floor, 50㎡ on the 3rd floor, and 50㎡ on the 4th floor

The key point here is the concept of “total floor area”. This is the sum of the floor areas of each level of the building, with some parts such as balconies and common areas possibly being excluded from the calculation.

Building images based on floor area ratio

Floor Area Ratio	Building Image on Same Site
100%	A single-story building covering the entire site, or a two-story building covering half the site
200%	A two-story building covering the entire site, or a four-story building covering half the site
300%	A three-story building covering the entire site, or a nine-story building covering 1/3 of the site
400%	A four-story building covering the entire site, or a sixteen-story building covering 1/4 of the site

Hidden Features of Properties Revealed by Floor Area Ratio Listings in Real Estate Advertisements

Real estate advertisements and flyers always include floor area ratio information.

1. The difference between legal floor area ratio and actual usage ratio
2. Legal floor area ratio of 500% with actual usage of 450% → Room for rebuilding
3. Usage at the legal maximum → May be difficult to secure the same scale in future rebuilding
4. Surrounding environment predicted from floor area ratio
5. Floor area ratio of 200% or less → Possibility of a quiet residential area with mainly low-rise houses
6. Floor area ratio of 800% or more → Possibility of a commercial area with high-rise buildings
7. Material for judging property rarity
8. A low-rise condominium using only 150% in an area with a floor area ratio of 300% → High rarity
9. A condominium built using the maximum floor area ratio → Typical property

When selecting a property, look not only at the floor area ratio value but also compare the legal floor area ratio and the actual usage ratio. The larger the difference, the more likely it is to maintain future rebuilding and value. By checking the floor area ratio of surrounding buildings, you can also predict future changes in the living environment.

The Difference Between Building Coverage Ratio and Floor Area Ratio—Two Indicators Easily Confused When Choosing a Condominium

Floor area ratio and building coverage ratio are terms often heard when purchasing a condominium, but many people confuse the difference between them. These two indicators are important points in property selection, so let’s understand them clearly.

The Basics of Building Coverage Ratio and Its Relationship to Floor Area Ratio

Building coverage ratio refers to “the ratio of building area (the horizontal projection area of the building) to the site area.” Simply put, it is the “ratio of area occupied by the building on the land”.

The decisive difference between the two

Feature	Building Coverage Ratio	Floor Area Ratio
Area considered	Building area (area seen from above)	Total floor area (sum of all floor areas)
What it indicates	The “spread” of the building relative to the site	The “volume” of the building relative to the site
Affected elements	Sunlight/ventilation/disaster prevention performance	Population density/townscape/living environment
Typical values	30%-80%	100%-1000%

For example, on a 100㎡ site with a building coverage ratio of 60% and a floor area ratio of 200%:

• Building coverage ratio: Up to 60㎡ of building footprint can be created
• Floor area ratio: Up to 200㎡ of total floor area can be built

Based on these combinations, building designs such as the following are possible:

• 1st floor 60㎡ + 2nd floor 60㎡ + 3rd floor 60㎡ (total 180㎡)
• 1st floor 50㎡ + 2nd floor 50㎡ + 3rd floor 50㎡ + 4th floor 50㎡ (total 200㎡)

What is the Ideal Balance? Reasons to Check Both

Building coverage ratio and floor area ratio interact with each other and determine the characteristics of a condominium.

Reasons to check both

1. Material for judging living environment comfort
2. Low building coverage ratio and high floor area ratio → High-rise type with spatial margin on the site
3. Both building coverage ratio and floor area ratio are low → Suburban-type condominium with low height and margin on the site
4. Evaluation of future potential
5. Both have room → Flexibility for future rebuilding or change of use
6. Both are at their maximum → Possibility of limited future options
7. Balance with price
8. If there is a difference in both values within the same area → Possibility of areas with different uses or special conditions

When choosing a condominium, not only the layout of the exclusive area but also these indicators including the “characteristics of the entire building” are important judgment materials. Choosing a property with good balance leads to maintaining long-term asset value.

Condominium Floor Area Ratio and Rebuilding—The Relationship That Affects Future Asset Value

One thing that many people overlook when purchasing a condominium is the “relationship between floor area ratio and rebuilding.” This relationship greatly affects the future asset value of the condominium, so it is important to understand it before purchasing.

The Impact of Floor Area Ratio Margin on Rebuilding Possibilities

As condominiums age, they eventually reach the time for rebuilding. At that time, floor area ratio takes on significant meaning.

Why does floor area ratio affect rebuilding? There are mainly two reasons:

1. Impact of regulatory changes
2. If the floor area ratio has been reduced after the current condominium was built, rebuilding at the same scale may not be possible
3. Such properties become “existing non-conforming buildings” and risk future value decline
4. Economics of rebuilding
5. Room in floor area ratio → Possibility of increasing the number of units when rebuilding → Reduction of cost burden
6. At maximum floor area ratio → Limited to same scale rebuilding → Risk of increased resident burden

Actual examples

Case	Floor Area Ratio Situation	Impact on Rebuilding
Property A	Legal 400%, used 350%	Room available, scale expansion is an option
Property B	Legal 300%, used 300%	Same scale is the limit
Property C	400% at construction → 300% now	Existing non-conforming, downsizing required

How to Identify “Existing Non-Conforming” Condominiums That Are Difficult to Rebuild

“Existing non-conforming” buildings are those that were legal at the time of construction but no longer conform to current laws due to law amendments. They have a significant impact on future asset value.

Effective identification methods

1. Check construction year and law amendment timing
2. Properties built before 1981 under old earthquake resistance standards
3. Properties in areas where land use zones have changed
4. Comparison of property documents and current regulations
5. Actual floor area ratio > Current legal floor area ratio → High possibility of existing non-conformance
6. Current legal floor area ratio can be confirmed with the municipality
7. Comparison with surrounding environment
8. Noticeably taller than surroundings → Caution needed
9. The only high-rise in a residential area → Possibility of existing non-conformance due to law amendments

When purchasing a condominium, it is important to consider not only the current living environment but also the possibility of future rebuilding. Especially for those considering long-term ownership, be sure to check the relationship between the property’s floor area ratio usage status and current legal regulations.

Condominium Floor Area Ratio Relaxation and Exclusions—Special Rule Knowledge That Benefits You

There are special “relaxations” and “exclusions” from the floor area ratio regulations. This knowledge is very advantageous when choosing a condominium.

Four Conditions for Floor Area Ratio Relaxation and Application Examples

Floor area ratio relaxation is a system that allows construction exceeding the legal floor area ratio under certain conditions.

1. Relaxation based on front road width
2. When facing a road with a width of 6m or more but less than 12m, and within 70m of a “specified road” with a width of 15m or more
3. Relaxation due to securing public open space
4. Floor area ratio bonus → For providing publicly accessible open space
5. Often adopted in high-rise condominiums
6. Utilization of the comprehensive design system
7. Significant relaxation → For securing public open space on sites above a certain size
8. Widely used in super high-rise condominiums
9. Special exceptions such as urban regeneration special districts
10. Relaxation exceeding normal restrictions → For urban regeneration contribution plans
11. Used in large-scale redevelopment

Real examples: Large-scale complex facilities such as Roppongi Hills and Tokyo Midtown were built utilizing these relaxation systems.

Cases Where Condominium Common Areas Are Excluded from Calculations and How to Verify

Certain parts are “excluded” (not counted) in floor area ratio calculations:

1. Some common areas
2. Common corridors & elevator halls → For improving living environment
3. Entrance lobbies → To encourage creation of open spaces
4. Parking & bicycle spaces
5. Mechanical parking → Excluded from floor area ratio
6. Drive-in parking → Excluded under certain conditions
7. Equipment-related spaces
8. Elevator shafts → Completely excluded
9. Stairwells → Excluded for disaster prevention purposes
10. Disaster prevention & energy-saving equipment
11. Emergency generator rooms → For strengthening disaster prevention
12. Energy-saving equipment → To promote environmental considerations

Exclusion utilization examples

• High-rise condominiums → Realization of wide corridors & luxurious lobbies
• Large-scale condominiums → Compatibility of adequate parking and unit area

When considering a purchase, check the “exclusive area ratio” (ratio of exclusive area to total floor area). Properties with a low value may have enhanced common areas by utilizing exclusion regulations.

When visiting a condominium, it is good to ask the sales representative about the application status of floor area ratio relaxations and exclusions. The margin in the actual usage rate compared to the legal floor area ratio is also a factor in judging asset value.

Summary: Understand Floor Area Ratio to Achieve a Successful Condominium Purchase

In condominium purchases, knowledge of floor area ratio is an important indicator for discerning the essential value of a property that is not visible from just the layout and price.

It is important to make a comprehensive judgment considering the difference between legal floor area ratio and actual usage rate, harmony with the surrounding environment, balance with the building coverage ratio, exclusion and relaxation status, and the possibility of future rebuilding.

Choose a property that matches your lifestyle and values with an understanding of how floor area ratio affects the actual living environment and future potential. I hope this knowledge will help you make a wise condominium selection.