Construction Cost Estimating


How to calculate the plinth area of a building

Plinth area alias built-up area stands for the entire area engrossed by the building along with the area of inside and outside walls. Normally, it remains 10% to 20% more than the carpet area.

In short form, it is represented as follow :-

Plinth Area = Carpet Area + Thickness Of All Walls + Balcony

Calculation of Plinth Area: For calculation purpose, the lengths and widths should be calculated closest to 0.01m and areas are rounded to 0.01 m2. In Case of feet system, length is computed to closest 1 inch.

At the time of calculation, individual measurement should be taken individually for the following item:

• Basement
• Floor exclusive of cladding (stilled floor)
• Floors including top floor which may be partly covered
• Garage
• Mezzanine floor

While making calculation of plinth area, the following areas are comprised :-

1. Area of the wall at the floor level, exclusive of plinth offsets. If any common walls exist among two buildings, half of the area of such walls should be included in the plinth area. If building contains columns extending apart from the cladding, the plinth area is calculated up to the outside face of the cladding.

2. Areas of the inside shaft for sanitary installations and garbage chute, electrical, telecom and firefighting services provided these do not surpass 2 m2 in area.
3. Vertical duct for air conditioning and lift well along with landing.
4. Staircase room or head room except for terrace level.
5. Machine room
6. Porch

7. Open extensions of veranda, balconies and parapets, if the area is protected with extensions, entire area should be comprised in plinth area, if the area is un-protected with extensions, 50% of the area should be comprised of.
8. Recess by cantilevering beyond outside walls. If the recess height remains up to 1.0 meter, 25% of such area should be considered. If the recess height remains 1.0 to 2.0 meters, 50% of such area should be considered. If the recess height surpasses 2.0 meters, 100% of such area should be considered.

The following should be excluded from the plinth area:

a) Area of loft
b) Area of architectural band, cornice, etc.
c) Area of vertical sun breaker or box louver projecting out and other architectural features, as for instance slab projection for flower pot, etc.
d) Open platform
e) Terrace
f) Open spiral/service stair cases
g) Area of mumty, machine room, towers, turrets, domes extended over terrace level.

How to calculate the plinth area of a building