1. RICS Senior Professional Route
Case Study 2
Design parameters for efficient High Rise Building Floor Plans (2015)
Introduction
In 2013 a private developer embarked on a 40 acre residential community with all
necessary amenities to make it a self sufficient balanced work life community
comprising of 27 high rise towers (55 habitable floors) on a common podium. The
first three buildings (Tower 2A , 2B and 3B) that were launched for sale comprised
predominately of 2BHK and 3BHK units .The subsequent towers launched in 2014
( Towers 1A and 1B) were also 2BHK and 3BHK . The project is being phased to
complete in 2026.

2. The developers, with a view to deliver a built environment with a high quality of life
experiences within the community provided for large open spaces for safe active
and passive recreational activities while at the same time maximising the full potential
of the land , decided to build high rise towers to meet these objectives.
The key issues
Based on estimated cost of construction and current sale price realization of the local
market, the first three buildings were not financial viable (although due care was
taken while designing the first three buildings) and hence as a consequence the
management decided to analyse the existing typical building floor plans with a
view to understand the various components that contribute to make a building
plan efficient which can be used as parameters to benchmarks future building
designs in the said community . Therefore the relevant key issues for the
Management were to identify design parameters and establish acceptable
ranges / benchmarks for the same through analysis of the existing plans. Based
on the review of the plan the following key components were identified as key
issues:
• Ratio of core to construction area.
• Ratio of Walls, Core area, elevational features to Floor Plate.
• Ratio of components that make up the core to the overall Core area.
• Structural efficiency of the building.
My role and personal involvement:
My role as Chief Architect was to study and analyse the existing floor plans to identify
planning elements that contribute to the making of an building plan, understand the
underlying reasons for the same and establish acceptable ranges based on minimum
ergonomic design standards and its impact on aesthetics, cost and construction
technology and time for such high rise buildings.
Problems faced and how I resolved them:
1st
Challenge: Ratio of Core area to Construction Area.
Solution: Based on the analysis it was established that lower the ratio the more
efficient is the building, however the acceptable range for high Rise buildings is
between 15% - 20 % with an upper limit of 25% in exceptional cases.
Table 1:
Building Ratio of Core to total construction area
1A and 1B 19.60%
2A and 2B 27.90%
3B 20.60%

3. 2nd
Challenge: Ratio of Walls, Core area, elevational features to Floor Plate.
Solution: The analysis established that lower the ratio of walls, core and elevational
features (boxing, weather shades, bands etc) the more efficient is the building,
however higher the carpet / usable ratio to abovementioned components the more
efficient the plan. The acceptable range for high Rise buildings is around 30 % with
an upper limit of 35%. It must be highlighted that more number of flats to a floor the
efficiency improves for the same components.i.e. Six flats /floor are more efficient
than four flats / floor.
Table 2:
Building Carpet
area
Terrace Usable Wall Core Elevational Total
1A and 1B 58.6% 7.3% 65.6% 13.3% 20.7% 0.5% 100%
2A and 2B 54.3% 0.0% 54.3% 13.4% 31.5% 0.9% 100%
3B 61.6% 0.0% 61.6% 14.0% 23.5% 0.8% 100%
3rd
Challenge: Ratio of components that make up the core to the overall Core area.
Solution: The analysis established that the Passages and Lift lobby are critical to the
efficiency of the Floor plan and a ratio between 40 – 50 % together is acceptable ,
above which it becomes unacceptable .Staircase by default would have to meet Bldg
codes and a range between 10% - 15 % is good , 15 % - 20% is acceptable . The
lower wall ratio the better! Refer Table 3.
Table 3:
Building Stair 1 Stair 2 Lift Lobby Passage Wall Total
1A and 1B 17.2% 17.2% 12.8% 36.2% 16.6% 100%
2A and 2B 12.8% 12.8% 15.4% 55% 6.9% 100%
3B 21.6% 21.6% 24.2% 20.9% 11.6% 100%
4th
Challenge: Structural efficiency of the building.
Solution: It was observed that the overall shape of the Building as a whole played
an important role in the structural efficiency of the building impacting consumption of
Steel and thereby cost. It was found that 3B (@8.71kg/sft) was the most structurally
efficient among the three, followed by 2A/2B (@8.45kg/sft). The building shape of
1Aand 1B (@7.64kg/sft ) for 45 habitable floors did not help in its structural efficiency
although was better on the planning parameters wrt 2A, 2B and 3B. The parameter to
assess is the steel co-efficient ratio i.e. steel consumption / unit plan area of the total
building taken as a whole. It was felt that around 7.5 kg/sft to 8.5 kg/ sft. should be
the target coefficient for such high rise buildings.

4. Outcome and conclusion
A holistic approach to building plan design is critical to an efficient floor plan that
balances functional requirements, aesthetics, costs, constructability and time.
The lessons I learnt on account of this exercise are as follows:
• Parmeters identified should be part of the design brief to the Architects.
• Structural coefficients should be benchmarked as conditions of approval.
• Unrealistic efficiency benchmarks should be avoided.
The above exercise resulted in a useful tool for management to benchmark designs
approvals going forward.