Plinth Area
Plinth area is the covered built-up area that is measured at the floor level of any storey of the building( or even at the floor level of the basement of the building).
Plinth area is also commonly known as the built-up area.
In other words, the plinth area can also be defined as the total area occupied by the building as a whole. The total area refers to the entire area occupied by the building with the inclusion of the external walls and the internal walls.
In general practice, the plinth area is 10 to 20% greater than the carpet area of the building.
The calculation of the plinth area can be easily done by taking the measurements of the external dimension at the floor level of the building but the open spaces, courtyards, offsets of the plinth and the cantilever projections if present must be excluded. However, the porches other than the cantilevered must be included in the plinth area.
Elements to be Included in Plinth Area
The elements that are included in the plinth area can be listed as follows:
a. The area of all the floors of the building at the floor level without including the offsets of the plinth.
b. The internal shafts that are less than 2 sq.m in the area provided for the sanitary fittings, lifts, ducts for pipelines, air conditioner etc.
c. The parasitic area and the multi-area at the terrace level of the building.
d. The area of the porches other than the cantilevered.
Elements to be excluded from the Plinth Area
The elements that must be excluded from the plinth area are as follows:
a. The area of the loft of the building.
b. The internal shafts that are greater than 2 sq.m in area.
c. The elements that project above the terrace level such as domes, sunshades etc.
d. Any type of architectural elements such as cornices that may be present in the building.
e. Any projections present in the building such as vertical sun breakers.
Things to be considered during the Measurement of Plinth Area
During the measurement of the plinth area, the dimensions i.e. the lengths and the widths must always be measured up to an accuracy of 0.01m. The calculated area must also be rounded to 0.01m². In case, the measurement system unit is feet, then the length must always be measured up to the nearest 1inch.
The elements that must be measured separately during the plinth area measurement are as follows:
a. Basement
b. Stilled Floor i.e. the floor without cladding
c. Garage
d. All the floors of the building including the top floor even if it is partially covered.
e. Mezzanine Floor
Codal Provision for Plinth Area
The regulations for the plinth area is given in IS 3861:2002 code. According to Sub-Clause 2.1 of IS 3861:2002, the plinth area is referred to as the built-up area that is covered and measured at the floor level of both the basement and storey levels.
The provision for the measurement of the plinth area is given in Clause 5 of the same code. According to Sub-Clause 3.1 of IS 3861:2002, the plinth area measurement must be done such that it includes all the built-up covered areas that are measured for the categories that are given in Sub-Clause 3.2 of the same code and must also include the areas that are listed in Sub-Clause 4.1.1 and must not include the areas that are listed in Sub-Clause 4.1.2.
As per the provision of Sub-Clause 4.1.1, the following must be included in the plinth area:
a. The area of all the walls at each floor level without including the offsets of the plinth and in the case columns are projected beyond the cladding, the area up to the external facing of the cladding must be taken. If such cladding consists of the corrugated sheet then the plinth area must also include the area up to the outer edge of the corrugation.
b. The area of the shafts if any present for the sanitary fittings, pipelines, telecommunication cables, electrical fixtures, fire-fighting and air-conditioning vents etc.
c. The staircases, if any.
d. In the case of presence of any verandahs with parapets, the total percent of the area that is protected by the upper projections must be included. While only 50 %area must be taken in case the balcony is not protected.
e. In the case, an alcove is formed due to the cantilevering of a slab that is beyond the external wall, about 25% of the area must be taken for the alcove that has a height up to 1m. While 50% of the area of the alcove must be taken for the alcove that has a height greater than 1m but up to 2m and for the alcove with height more than 2m, 100 % of the area must be included in the plinth area.
As per the provision of the code, the following must be excluded from the plinth area:
a. Loft area
b. Area of any architectural band or cornices, if present.
c. Area of open platforms, if any.
d. Area of any architectural element that is projecting out from the building such as projected slabs.
e. Any service staircase or spiral staircase, if present.
f. Area of any projections from the terrace such as towers, turrets etc.
Inclusion of Wall Area in the Plinth Area Calculation
During the calculation of the plinth area, the wall area of the building must also be included at all storey of the building. The wall area of the building refers to the area that is occupied by the floor in consideration at any floor level on the plan of the building. The wall area also includes the area of the finishing such as dado tiles that have a height greater than 1m from the level of the floor finish.
The wall area of the building includes the following:
a. The area of the portion that is occupied by the doors and windows on the plan of the building.
b. The area of the intermediate columns and other similar structures that lie within the plinth area of the building.
c. The area of the pilasters greater than 300cm², if any.
d. The area of any flues or ducts that may be present on the wall.
e. The area of any built-in cupboards, shelves and other similar structures that are present within a height of 2.2m from the floor level.
f. The area of the fireplace that extends beyond the facing of the wall in the bedrooms or the living room.
The wall area of the building does not include the following:
a. The area of the pilasters less than 300cm² in area.
b. The area of the platforms that project beyond the facing of the wall.
Difference between Plinth Area and Carpet Area
Plinth Area | Carpet Area |
The plinth area of the building is also commonly referred to as the built-up area. | The carpet area of the building is also commonly referred to as the usable area. |
It refers to the area that is obtained by multiplying the out-to-out dimensions of the building at any floor level. | It refers to the area that is obtained by subtracting the area of the outer and inner walls of the building from the total floor area of the building. |
In other words, the plinth area is the area that lies within the outer to outer dimensions or the walls of the building. | In other words, the carpet area is the area where the carpet can be laid inside the building. |
Difference between Plinth Area and Super Built Up Area
The major differences between the plinth area (built-up area) and the super built-up area can be tabulated as follows:
Plinth Area | Super Built-Up Area |
Plinth area is the area that is calculated by adding the carpet area of the building and the thickness of the walls of the building. | Super built-up area is the area that is calculated by adding the plinth area and the external spaces and projections such as the lobby, elevators etc. |
It is also referred to as the total built-up area of the building. | It is also referred to as the total saleable area. |
Mathematically, Plinth area/ Built-up Area= Carpet Area of the building + area of the balcony + areas of the walls. | Mathematically, Super Built-Up Area = Carpet Area * (1+ Loading Factor) |
Numerical Example of Plinth Area Calculation from the Plan of a Building
# Calculate the plinth area from the given drawing of a building.
Solution,
From the drawing, it is clear that the thickness of the external wall is 13.5”. First, let us convert the dimension into feet,
13.5” = 13.5/12 = 1.125’
Now,
Total length of the external walls = external thickness of walls + length of rooms + thickness of internal wall
= 2* 1.125 + 14 + 14 + (9/12) (converting 9” to ft)
= 31 ft
Similarly,
Total external breadth of the walls = thickness of each external walls + width of rooms + thickness of internal wall
= 12 + 8 + 2 * 1.125 + (9/12)
= 23 ft
Hence,
Plinth Area of the Building = Area of the out to out dimensions
= 31 ft * 23 ft
= 713 sq.ft
Note:
If 14′ * 8′ is given as room measurement;
a. The first value is always an x-direction value.
b. The second value is always a y-direction value.
This is also important for you in land measurement, AutoCAD, etc.