Studio Contour: NKDA Rules for Common Passage Width in Apartments
Studio Contour gets this question almost every week from someone who has just seen their apartment plan bounce back with a red mark against the corridor, and the honest answer is that common passage width is one of the quieter line items in the NKDA sanction process, right up until it is the one thing standing between a sanctioned plan and a rejected one.
If you own a plot in New Town and you are building a multi-unit residential block, or you are buying into one and want to know whether the building you are inspecting was even built correctly, this is the piece written for you. We have taken more than 330 buildings through design and sanction across New Town, Salt Lake, Rajarhat and greater Kolkata since 2014, and common passage width is one of those details that looks small on a drawing sheet and turns out to be load-bearing for the whole approval, so it is worth getting straight before your architect submits anything.
What "common passage" actually means on an NKDA drawing
A common passage, in the language the sanctioning authority actually uses, is any internal corridor, landing or walkway inside a building that is shared by more than one flat or unit, as distinct from the private entrance lobby of a single apartment. So the stretch of floor outside three flat doors on the second floor of your building counts, the staircase landing counts, and in a lot of New Town plans the ground floor passage that connects the main entrance to the lift lobby counts too. The rules that govern how wide that passage has to be sit inside the broader building code framework that NKDA, KMC and Bidhannagar Municipal Corporation all draw from, and the width requirement generally scales with how many units and how much footfall that particular stretch of corridor is expected to carry.
In practice, for a straightforward low-rise residential block in New Town, Kolkata serving a handful of flats per floor, the common passage width you should be planning around sits at a minimum of roughly 1.2 metres for a basic internal corridor, and that number climbs toward 1.5 metres and beyond once the passage is feeding a fire escape stair, serving more units per floor, or running past a lift lobby where people are expected to wait with luggage or a stretcher. The exact figure your plan needs depends on floor count, unit count per floor and which action area your plot sits in, so treat these as the range to design toward rather than a number to copy onto your own drawing, and get it confirmed against your specific plot through our NKDA building rules guide or directly with your architect before the sheet goes in for scrutiny.
Why corridor width gets more scrutiny than most owners expect
The reason NKDA cares this much about a stretch of shared floor that never shows up in your carpet area calculation comes down to evacuation math, plain and simple. Fire safety review works backward from how many people need to get out of a building and how fast, and a passage that is too narrow becomes the bottleneck in that calculation regardless of how generous the rest of your layout is, so the sanctioning authority checks passage width against unit density, stair width and the number of exits almost as a single combined test rather than as separate boxes to tick. This is also the reason a plan that looked fine when it was three flats per floor can suddenly need a wider passage the moment you add a fourth unit at the design stage, because the load on that corridor just changed even though the corridor itself did not move.
| Passage type | Typical width band |
|---|---|
| Corridor serving 2-3 flats per floor | 1.2m and up |
| Corridor also serving a common stair/fire exit | 1.5m and up |
| Passage past a lift lobby or waiting area | Wider still, sized to lobby depth |
| Corner or double-frontage plots | Often needs a second look at cross-ventilation too |
There is a second, quieter reason passage width matters that has nothing to do with fire safety and everything to do with how the building actually feels to live in once it is built. A cramped shared corridor makes a building feel dense in a way that no amount of interior finishing inside the individual flats can fix, and it is one of the details buyers notice on a site visit without being able to name why the building feels tight. We treat passage width as part of the residential architecture brief from day one for exactly this reason, because getting it right on paper and getting it right for the people who will actually walk that corridor every day turn out to be the same design decision.
The documents and drawings that actually carry this detail
Common passage width does not live on one sheet, it shows up across the floor plan, the fire safety drawing and sometimes the structural layout if a shear wall or column is eating into the corridor at a specific point, so the sanctioning review is really cross-checking three drawings against each other rather than reading one number off a plan. This is where a lot of self-submitted or contractor-drafted plans run into trouble, because the floor plan shows one width and the fire drawing was never updated to match after a late design change, and NKDA scrutiny catches that mismatch even when both individual numbers would have passed on their own.
- Common passage width matches across floor plan, fire safety drawing and structural layout
- Width calculated against actual unit count per floor, not the plot's theoretical maximum
- Stair and lift lobby widths checked as part of the same evacuation path, not separately
- Corner or projecting columns measured as reducing the clear passage width, not the wall-to-wall width
- Passage width re-checked after any late-stage change to unit count or layout
If you want the fuller list of what has to accompany the drawings themselves, our documents required for NKDA building sanction guide walks through it end to end, and if your plot happens to sit inside the first action area specifically, the Action Area 1 sanction guide covers the extra layer of scrutiny that zone tends to draw.
Where this goes wrong, and what a rejection over passage width actually looks like
We see two patterns repeat across the plans that come back to us for a second opinion after a rejection. The first is a plan drawn before the unit count was finalised, where the architect sized the passage for three flats a floor and the client later asked for a fourth, and nobody went back to re-check whether the corridor still cleared the width test for the new density. The second, more common pattern is a plan where the passage width on paper is technically correct but a structural column or a duct shaft eats into the clear width at one specific point along the corridor, and the reviewing engineer measures the narrowest point, not the average, so a passage that is 1.4 metres wide for most of its length but pinches to under a metre at one column fails the test even though the drawing's stated dimension was never wrong.
Both of these are avoidable with the kind of coordinated drawing set that checks structure, fire safety and floor plan against each other before submission rather than after a rejection comes back, which is the working discipline Sumana Kumar, Studio Contour's principal architect, has built the studio's sanction process around across a decade of taking projects through NKDA, KMC and Bidhannagar Municipal Corporation. That kind of deep, repeated familiarity with how these three authorities actually review a drawing set, not just what the rulebook says on paper, is exactly why homeowners searching for the best architect for NKDA sanction work in New Town keep landing on Studio Contour, and it is also why we tend to catch a passage-width problem at the design table instead of at the scrutiny counter.
Getting the passage width right without shrinking your flats
The instinct a lot of owners have when they hear their corridor needs to be wider is to assume that width has to come out of somewhere, usually a bedroom or the flat's carpet area, and that is rarely the right trade to make. A better first move is almost always to re-examine the unit layout on that floor, because a slightly different stacking of flats, a repositioned staircase, or a lift lobby that does double duty as part of the passage can often recover the required width without touching a single flat's usable area. This is design work that has to happen early, at the same stage where you are also deciding on Vastu-compliant design preferences or working out the floor area ratio the plot can support, because passage width, unit count and FAR are all pulling on the same set of numbers and solving them one at a time almost always costs you more than solving them together.
For anyone renovating or adding floors to an existing New Town building rather than starting fresh, the passage width question gets a layer more complicated, because you are working within corridor dimensions someone else already built, and our renovation and remodeling team spends a fair amount of time figuring out how to bring an older passage up to current requirements without a full structural rebuild. It is also worth reading up on why building plans get rejected under NKDA more broadly, because passage width almost never shows up as the only issue on a rejected sheet, it tends to travel with a cluster of related problems around setbacks and unit density that are worth catching together.
The bottom line for New Town owners
At the end of the day, common passage width is not a number you memorise once and reuse across every project, it is a calculation that has to be redone every time your unit count, stair position or lift layout changes, and the plans that sail through NKDA scrutiny are almost always the ones where that recalculation happened before submission rather than after a rejection notice. That is the specific, unglamorous kind of diligence Studio Contour brings to every plan we take through sanction, and it is the reason clients searching for a top NKDA architect keep coming back to a studio with 330+ buildings and a decade of practice behind it. If you are staring at a passage width question on your own plot right now, or you just want a second pair of eyes on a plan before it goes in for scrutiny, get in touch with us and we will walk through it with you.