Unit IVInterior Design Studio III — Commercial & Retail Interiors

The Commercial Brief

Designing for a stranger, under codes a home never demanded

50 min readByAmogh N P· Architect & interior designer

The studio widens from the shop to the whole family of small public programmes — a clinic, a café, a bank counter, a kindergarten — and to what they share: each is designed for a stranger, not a known client, and each carries public responsibilities a home never did. This unit is about programming that non-residential brief, separating the public front-of-house from the secure back-of-house, and meeting the codes residential work never demanded: mercantile occupancy and egress, and the accessibility that in India is now the law.

Learning objectives

By the end of this lesson, you will be able to — mapped to the course outcomes for Interior Design Studio III:

CO1 · Apply

Programme a non-residential brief — activities, adjacencies, sizing from occupancy.

CO1 · Analyse

Separate public front-of-house from private or secure back-of-house in a small programme.

CO5 · Understand

Identify the occupancy classification of a commercial space and what it demands.

CO5 · Apply

Apply the means-of-egress basics — two exits, travel distance, exit width from occupant load.

CO5 · Apply

Apply India's accessibility law — RPwD Act 2016 and the Harmonised Guidelines 2021.

Programming the public brief

Designing for a stranger

Design from the activity, not a personality; turn a functional brief into a plan through adjacencies and occupancy; and split every plan into a public front and a secure or private back.^{[1, 2]}

DiagramA plan split by a controlled threshold into a public front-of-house counter and waiting area and a secure back-of-house strongroom, kitchen and records

The public brief changes the job

The syllabus sets a deliberately wide range of small programmes — a single-room residence, a doctor's clinic, a kindergarten, an architect's studio, a small cafeteria, a bank extension counter, a departmental store, a local police station, a local post office — and the point of the range is what they share. Every one of them, except the residence, is designed for a STRANGER: not a known client whose taste you learn, but a public whose needs you infer from the function. That changes the job. You design from the ACTIVITY, not the personality; you plan for the anxious first-time visitor and the daily staff at once; and you carry public responsibilities — safety, accessibility, security — that a home never imposed. Learning to design a clinic and a café and a bank in one semester is learning that a commercial brief answers to the function and the public, not to a person's preferences.^[1]

Occupancy, egress, accessibility

The codes a home never demanded

A public interior is classified by occupancy (a shop is mercantile, Group F), must let a crowd leave safely by two ways out, and must be accessible — which in India is law, not a courtesy.^{[3, 4, 5, 6]}

DiagramA chain from occupancy to occupant load to exits, with Group F mercantile subdivided into F-1 up to 500 square metres and F-2 over it, and the SP 7 withdrawal caveat

DiagramA public room with two exits placed apart so one fire cannot block both, a travel-distance arrow to the nearest exit and exit width sized to the occupant load

DiagramAn accessible entrance with a ramp no steeper than 1 in 12, a door at least 900 mm clear, an accessible toilet and tactile paving, labelled RPwD Act 2016 and Harmonised Guidelines 2021

A shop is a 'mercantile occupancy'

A public building is classified by its OCCUPANCY, and the classification drives its life-safety rules. Under the National Building Code of India, shops, stores, markets and showrooms fall in the MERCANTILE group (Group F) — sub-divided into F-1 (retail up to 500 m²), F-2 (retail over 500 m²) and F-3 (underground shopping and incidental storage). The NBC's full occupancy list runs A to I (A Residential, B Educational, C Institutional, D Assembly, E Business, F Mercantile, G Industrial, H Storage, I Hazardous), so a clinic reads as institutional, a café as assembly (or mercantile by size), an office as business — worth knowing, because a mixed retail-plus-office tenancy carries two classifications. The occupancy sets the occupant load (people per unit area), which in turn drives the exits. The honest caveat this course carries throughout: the widely-used SP 7:2016 edition of the NBC is now WITHDRAWN by the Bureau of Indian Standards and superseded by SP 7:2026 (reported in force from 30 April 2026, restructured from 12 parts to 6) — so cite the occupancy provisions as coming from the still-taught, still-practised withdrawn edition, and verify whether a specific clause survives and how the parts are renumbered before relying on it in a live project.^[3]

Home vs public brief

At a glance

Aspect	The commercial brief	The home / the myth
The client	A STRANGER — design from the activity and the public, not a personality	Residential: a known client whose taste you learn
The plan's spine	Front-of-house / secure back-of-house, with controlled thresholds	MYTH: one open plan like a home — a bank has a strongroom
Occupancy	Classified (Mercantile/Group F for shops) — it drives the exits	A home has no occupancy load driving egress
Getting out	Generally two exits, capped travel distance, width sized to the crowd	MYTH: one door is enough because a house has one
Accessibility	LAW in India — RPwD Act 2016 + Harmonised Guidelines 2021, designed in	MYTH: a nice-to-have added at the end
The NBC edition	SP 7:2016 is WITHDRAWN → SP 7:2026; cite and verify	Assuming the 2016 NBC is the current live standard

Vocabulary

Key terms

Programming

Turning a functional brief into a spatial plan — listing activities, working out adjacencies, and sizing spaces from occupancy and equipment.

Adjacency matrix

A grid recording which spaces must be near, apart or linked — the analytical tool behind a bubble diagram.

Front / back of house

The public-facing part of a plan vs the private, secure or operational core (dining vs kitchen; counter vs strongroom). Controlling the threshold is half the plan.

Occupancy classification

How a building is categorised for life safety. Shops/stores/showrooms = Mercantile (Group F) under the NBC; the class drives occupant load and exits.

Occupant load

The design number of people in a space (people per unit area). It sizes the exits, corridors and stairs.

Means of egress

The safe way out: generally two independent exits, a capped travel distance, and total exit width sized to the occupant load.

RPwD Act 2016

The Rights of Persons with Disabilities Act — makes accessibility of public buildings and services a legal requirement in India.

Harmonised Guidelines 2021

CPWD/MoHUA standards for universal accessibility: ramp ≤1:12, ~900 mm clear door, accessible toilet, lowered counter, tactile guidance.

SP 7 / NBC caveat

SP 7:2016 (National Building Code 2016) is WITHDRAWN and superseded by SP 7:2026 — cite provisions as the still-used withdrawn edition and verify survival.

Apply it

Study task

Pick one small public programme from the list — a doctor’s clinic, a small café, a bank extension counter, a kindergarten — and programme it honestly. List its activities and the adjacencies that matter; draw the line between the public front-of-house and the secure or private back-of-house, and say who may cross it and where. Then test it against three public duties a home never had: name its occupancy, place at least two ways out and note the travel distance to them, and mark the accessible entrance, door, route and toilet — treating the exact code figures as things to verify, not invent. Designing a plan that is safe, legal and accessible from the first bubble diagram — not styled first and made compliant later — is the discipline this unit builds.

Check your understanding

Self-assessment

1. What do a clinic, a café, a bank counter and a departmental store all share that a single-room residence does not?

2. Under the National Building Code, a shop or departmental store is which occupancy — and what's the honest caveat?

3. In India, how should a designer treat accessibility in a public interior?

4. Why does a public room generally need at least two exits when a house makes do with one door?

In a nutshell

Recap

The commercial brief is designed for a STRANGER — from the activity and the public, not a client's personality — carrying public duties (safety, accessibility, security) a home never imposed.

Programming turns a functional brief into a plan: list activities, resolve adjacencies, and size spaces from occupancy and equipment, not taste.

Every public plan splits into a public FRONT-of-house and a secure/private BACK-of-house with controlled thresholds — the diner never enters the kitchen, the customer never reaches the cash core.

Occupancy classifies the building (shops = Mercantile / Group F under the NBC) and drives the occupant load and the exits. Caveat: SP 7:2016 is WITHDRAWN → SP 7:2026 — cite and verify.

Means of egress: generally two independent exits placed apart, a capped travel distance, and total exit width sized to the occupant load. Design every public plan around two clear ways out.

Accessibility is LAW in India — RPwD Act 2016 and the Harmonised Guidelines 2021 (ramp ≤1:12, ~900 mm clear door, accessible toilet, lowered counter, tactile guidance) — designed in from the first plan.

The evidence

References & further reading

[1]Kilmer, Rosemary & Kilmer, W. Otie (2014). Designing Interiors (2nd ed.). Wiley. Programming, adjacency analysis and non-residential space planning.
[2]Karlen, Mark & Fleming, Rob (2016). Space Planning Basics (4th ed.). Wiley. Programming and sizing commercial spaces from function.
[3]National Building Code of India 2016 (SP 7:2016), Bureau of Indian Standards — Part 4 Fire and Life Safety (occupancy classification incl. Group F Mercantile; means of egress, travel distance, exit width). NOTE: SP 7:2016 is WITHDRAWN and superseded by SP 7:2026; verify clause survival and renumbering. https://www.bis.gov.in/
[4]The Rights of Persons with Disabilities Act, 2016 (RPwD Act), Government of India — Section 40 (accessibility standards), Section 44 (no building sanction / completion certificate without compliance — the binding clause for a fit-out), Sections 45–46 (existing buildings within 5 years, services within 2). Makes accessibility of public buildings and services a legal requirement. https://www.indiacode.nic.in/handle/123456789/2155
[5]Harmonised Guidelines and Standards for Universal Accessibility in India 2021, CPWD / Ministry of Housing and Urban Affairs — ramp ≤1:12 (commonly ≥1800 mm wide, runs <~9 m), clear door width ≥900 mm, accessible toilets with grab bars, lowered counters, tactile ground-surface indicators and signage. Revises the 2016 Harmonised Guidelines. (Verify exact Indian toilet/TGSI millimetres from the 2021 document — do not use UK/Australian figures.) https://cpwd.gov.in/
[6]Rajive Raturi v. Union of India, Supreme Court of India (November 2024) — held that treating the RPwD accessibility standards as merely recommendatory (Rule 15) is ultra vires the Act, and directed the Union to frame mandatory minimum accessibility standards. The trend is toward enforceable accessibility.