Different Types of Area Calculations in Buildings
Understanding different area calculations is essential for architects, builders, real estate developers, and buyers. These definitions, as per IS 3861:2002 and the National Building Code (NBC) 2016, help standardize measurements and ensure transparency in construction and real estate transactions. Below is a detailed explanation of the concepts, along with additional insights and examples.
1. Carpet Area (Net Usable Area)
Definition:
The carpet area is the actual usable area within the walls of a residential or commercial unit. It is the space where you can lay a carpet, hence the name. This area is exclusive of walls, balconies, and common areas.
Key Features:
- It is the most important metric for buyers as it reflects the actual living space.
- It is typically 70-75% of the built-up area, depending on the design and layout of the building.
Inclusions:
- Living spaces: Bedrooms, living rooms, dining rooms, study rooms.
- Functional spaces: Kitchen, bathrooms, store rooms, utility areas.
- Internal passages: Hallways or corridors within the unit.
Exclusions:
- Walls: Both internal and external walls are excluded.
- Balconies: Open or covered balconies are not part of the carpet area.
- Common areas: Lobbies, staircases, lifts, and other shared spaces.
- External ducts and shafts: These are excluded as they are not usable spaces.
Formula:
Carpet Area = Total Built-Up Area - Wall Thickness - Balconies - Common Areas
Example:
If a flat has a built-up area of 1,000 sq. ft., with wall thickness occupying 100 sq. ft. and balconies occupying 50 sq. ft., the carpet area would be:
Carpet Area = 1,000 - 100 - 50 = 850 sq. ft.
2. Built-Up Area (Plinth Area)
Definition:
The built-up area includes the carpet area plus the thickness of walls and other built-up spaces like covered balconies. It represents the total area covered by the structure.
Key Features:
- It is 10-15% larger than the carpet area due to the inclusion of walls and other structural elements.
- It is used for construction planning and building cost estimation.
Inclusions:
- Carpet area: All usable spaces within the unit.
- Wall thickness: Both internal and external walls.
- Covered balconies: If the balcony is covered, it is included.
- Internal ducts: Ducts used within the unit.
Exclusions:
- Open balconies: These are not included unless covered.
- Common areas: Staircases, lifts, and corridors are excluded.
- Open terraces: These are not part of the built-up area.
Formula:
Built-Up Area = Carpet Area + Wall Thickness + Covered Balcony Area
Example:
If the carpet area is 850 sq. ft., wall thickness is 100 sq. ft., and covered balconies occupy 50 sq. ft., the built-up area would be:
Built-Up Area = 850 + 100 + 50 = 1,000 sq. ft.
3. Super Built-Up Area (Saleable Area)
Definition:
The super built-up area includes the built-up area plus a proportionate share of common areas such as lobbies, staircases, lifts, and amenities like clubhouses, gyms, and gardens. It is the area used for pricing in real estate.
Key Features:
- It is 25-30% larger than the built-up area due to the inclusion of common spaces.
- It is also called the saleable area because it is the basis for calculating the cost of the property.
Inclusions:
- Built-up area: Includes carpet area, walls, and covered balconies.
- Common areas: Proportionate share of lobbies, corridors, staircases, lifts, and amenities like clubhouses, gyms, and swimming pools.
Exclusions:
- Open parking spaces: These are not included.
- Open terraces: These are excluded unless covered.
- Landscaped areas: These are not part of the super built-up area.
Formula:
Super Built-Up Area = Built-Up Area + Proportionate Common Area
Example:
If the built-up area is 1,000 sq. ft. and the proportionate common area is 300 sq. ft., the super built-up area would be:
Super Built-Up Area = 1,000 + 300 = 1,300 sq. ft.
Efficiency Ratio (Carpet Area to Super Built-Up Area)
Definition:
The efficiency ratio indicates the percentage of usable space (carpet area) in relation to the super built-up area. It is a measure of how efficiently the space is utilized.
Formula:
Efficiency Ratio (%) = (Carpet Area / Super Built-Up Area) × 100
Classification:
- Below 65%: Low efficiency (more common areas, less usable space).
- 65%-75%: Moderate efficiency.
- Above 75%: High efficiency (more usable space, fewer common areas).
Example:
If the carpet area is 850 sq. ft. and the super built-up area is 1,300 sq. ft., the efficiency ratio would be:
Efficiency Ratio = (850 / 1,300) × 100 = 65.38%
This falls under moderate efficiency.
Additional Notes:
1. Importance of Standardization:
- IS 3861:2002 and NBC 2016 provide standardized definitions to avoid discrepancies in area calculations.
- These standards ensure transparency in real estate transactions and construction billing.
2. Common Misconceptions:
- Many buyers confuse carpet area with super built-up area, leading to misunderstandings about the actual usable space.
- Developers often advertise the super built-up area, which includes common spaces, making the property seem larger than it actually is.
3. Practical Implications:
- Buyers: Should always ask for the carpet area to understand the actual usable space.
- Developers: Must clearly disclose all area calculations to maintain trust and compliance with regulations.
4. Legal Compliance:
- As per RERA (Real Estate Regulatory Authority), developers are required to disclose the carpet area in all property transactions, ensuring transparency.
Summary Table:
| Area Type | Definition | Inclusions | Exclusions |
|---|---|---|---|
| Carpet Area | Actual usable area within walls | Bedrooms, living rooms, kitchen, bathrooms, store rooms, utility spaces | Walls, balconies, common areas, open terraces, ducts |
| Built-Up Area | Carpet area + wall thickness + covered balconies | Carpet area, walls, covered balconies, internal ducts | Open balconies, common areas, open terraces |
| Super Built-Up Area | Built-up area + proportionate common areas | Built-up area, lobbies, staircases, lifts, clubhouse, gym, pool, garden | Open parking, open terraces, landscaped areas |
By understanding these definitions and calculations, stakeholders can make informed decisions and ensure compliance with regulatory standards. Always refer to IS 3861:2002 and NBC 2016 for precise measurements and guidelines.
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