Real estate basics part 2 – OSR, FSI, Loading and Construction Stages

Do you find yourself constantly Googling terms when you are talking with a real estate agent? Do not worry, you are one among many! While doing business that involves an under-construction building, it pays to know the real estate terms associated with the building stages and other processes. Loading Factor, FSI and OSR are terms used with respect to the area you will be charged for. The base cost may say something but the end result could cost you a lot more – the base cost may be in your budget but when costs like the common areas, maintenance charges, etc., are factored in, the total cost shoots up

Want to read up about Carpet Area, Built-Up Area and Super Built-Up Area? Know what exactly Developers mean when they use these terms, in Part 1 of our Real Estate Basics blog post series: 



In this post, we demystify construction jargon such as Loading Factor, OSR and FSI for you, so that you are not taken for a ride.


Loading factor

Loading factor can be defined as the area which includes the proportionate share of the common area for a flat which is determined by applying a multiplier to the carpet area. In general, builders include space around staircases and elevators as common areas while calculating the loading factor. Thus, loading factor, when combined with the carpet area, gives the super built-up area of a flat.

For example, if a builder puts 1.25 as the loading factor, then it means 25% of space has been added to the carpet area of the flat. If the carpet area of a flat is 500 square feet then the super built-up area of the flat can be calculated as:

500 sq ft + 500 x 25% = 625 sq ft.


What is the acceptable loading percentage?

Ideally, the loading factor should be below 30%. A loading factor beyond this limit implies that the home buyer gets a lesser carpet area. Bigger projects generally have a higher loading because of their range of amenities while smaller projects have a lesser loading factor. Land allotted by the Government has zero loading factor. However, the loading factor of large projects can be close to 60% depending on the premium facilities they provide.


Loading percentage of the most popular cities

Delhi NCR20-40%
Mumbai Metropolitan Region (MMR)40-60%

Real Estate Basics Part 2 – OSR, FSI, Loading & Construction Stages

OSR (Open Space Ratio)

Open Space Ratio (OSR) is a terminology commonly used in the development of residential spaces. OSR is calculated by dividing the total amount of open space (which is commonly owned on the residential land parcel which is proposed for development) by the total area of the entire land parcel (which is proposed for development). Areas on private lots which are buildable and any commonly-owned open space that is less than 320 contiguous sq ft are not counted as open spaces. Although, areas like parking lots and recreation areas are included in open spaces.

For example, if there are 4 acres of common open space and 8 acres of land parcel proposed for development, then the open space ratio is 50%.


Real Estate Basics Part 2 – OSR, FSI, Loading & Construction Stages

FSI (Floor Space Index)

FSI, meaning Floor Space Index, also known as Floor Area Ratio (FAR), is the ratio of total built-up area to the total area of the plot. The municipal council of a particular area is responsible for establishing the FSI limit in a certain range, in order to regulate the amount of construction and the size of the buildings in that area. Since FSI is a measure that combines the height and footprint of a building, regulating it ensures flexibility in the design of the building. Note that FSI is applicable on commercial buildings also.

For example, if for a particular plot area of 10,000 sq metres, an FSI of 1 is allotted, then, a construction of 10,000 sq metres would be allowed for the project.

Similarly, if the FSI is 1.5 and you have a land of 1,000 sq ft of land, then, you can build up to 1,500 sq ft of covered structure.  The formula is quite simple:

Plot Area x FSI = Built-up area 

Note: FAR of 1.5 is expressed as FSI of 150%

Also Read: All you need to know about Floor Area Ratio


Real Estate Basics Part 2 – OSR, FSI, Loading & Construction Stages


Advantages of FSI limit

The following are the advantages of FSI in different cities:

  1. It helps in maintaining the skyline of a city
  2. The average FSI value ensures the development of good projects.
  3. It helps in maintaining a balance between planned growth and development in the cities
  4. Helps in maintaining the ratio between open space and built space


Some facts about FSI

The FSI of a land or building depends on where it is located. FSI in old cities might be different from new ones. The cities can also change their FSI depending on the requirement of developmental projects. FSI also helps in determining the potential of the land.

Though there is a simple formula for calculating the FSI, it might be difficult to do so in places specific areas where the porch, basement, lift and others are not considered. However, what can be included under FSI calculation depends on the rules in one’s city.


Construction stages

You may choose to stay away assuming that the various construction stages don’t concern you, but if your business involves an under-construction flat, these stages will definitely help you.


Real Estate Basics Part 2 – OSR, FSI, Loading & Construction Stages

Knowing the real estate terms of all the stages in the building construction process and their significance will save you much trouble:

1) Mobilisation
Mobilisation is the process of making the plot ready for construction. The process generally involves building a fence around the plot, making necessary services available, transport of construction tools and equipment to the plot and building a shed for the labourers.

2) Ground work
The process of levelling the ground of the plot, benchmarking and cleaning the plot comes under the phase of ground work.

3) Sub-structure work
Sub structure work involves the construction of structures like the foundation, neck columns, grade beams, the ground floor, etc.

4) Super structure work
Super structure work involves the construction of the structures that are situated above the ground like columns, slabs, beams, staircases, etc.

5) Masonry work
Masonry work is a phase in which everything comes into shape and gets a face. It involves plaster work and levelling of the walls and ceilings. This stage is what prepares the project for the services work.

6) Services work
Services work includes electrical work, sanitary work, plumbing work, etc. It involves fixing lights and fans, bathroom fittings, toilet equipment and anything else that would be provided by the builder.

7) Finishing work
At this stage, it is time to give the final touch to the property. It involves painting and any kind of carpentry work like doors, door frames and, in some cases, false wooden ceilings.

8) Completion
Completion stage of the building construction process involves cleaning of the built property, final inspection and handover of the property to the buyer.

We hope these terms solve all the confusions you had regarding realtor jargons when it comes to starting a construction. If you have more questions, ask us!

Want to read up about Carpet Area, Built-Up Area and Super Built-Up Area? Know what exactly Developers mean when they use these terms, in Part 1 of our Real Estate Basics blog post series: 



Is FAR the same as FSI?

Yes, the terms FAR and FSI are interchangeably used.

How much can I build if the FAR is 2 and I have 10,000 sq ft?

You will be able to construct up to 20,000 sq ft of covered structure.

What is the finishing stage of construction?

As the name suggests, this is the last stage of construction and the work involves any kind of carpentry work, such as doors, frames, false wooden ceilings or painting.

(With inputs from Sneha Sharon Mammen)


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