How to read a floor plan

A floor plan is the most exact document in the whole sale: it draws, to scale, exactly what you are buying. A brochure render can flatter a room with a wide lens and an empty foreground; a sample flat can be dressed with furniture built to a smaller scale than yours will be. The plan does neither. Once you can read it – the symbols, the two kinds of dimension line, what a shaded box actually is – you can check a brochure’s claims against it, compare two units at a glance, and tell a marketing drawing from the plan the authority actually sanctioned.

This guide is not about the site or the neighbourhood; it is about the sheet of paper, or PDF, itself. It covers the symbols and conventions every plan uses, why the carpet area RERA makes a promoter quote is smaller than the plan’s own outer wall line suggests, how to compare room sizes without being fooled by furniture drawn to a flattering scale, and the difference between the plan you are shown and the one on file with the authority.

Keep both kinds of plan in mind as you read: the unit plan for the exact flat you are buying, and, where you can get one, the typical floor plan that shows it in context – the shafts, the stair, the neighbours on either side, and everything else a single unit’s plan leaves out.

Reading the plan’s symbols

Every plan is drawn to a stated scale – commonly 1:50 or 1:100 for a single unit, 1:200 or smaller for a whole floor – and every plan uses the same handful of symbols, whichever architect drew it. A thick pair of parallel lines is a wall; the gap between them is its thickness. A quarter-circle with a straight line is a door, swinging on the straight line’s far end. Two thin parallel lines across a gap in the wall are a window. A solid square, usually inside or against a wall, is a structural column. A hatched or shaded box, generally stacked directly above and below the same box on every floor, is a shaft: a service duct running the height of the building.

Dimensions can be given two different ways, and a plan does not always tell you which one you are looking at. An internal, or clear, dimension runs wall face to wall face – the space you can actually put a bed or a wardrobe into. A centre-line dimension runs from the centre of one wall to the centre of the next, which is always the larger number, because it counts half the thickness of each wall on either side. Indian plans also mix units: older and hand-drawn plans often give feet and inches, marked with ′ and ″, while a RERA filing and most current architects’ drawings use metres. Keep a rough conversion in your head – a metre is a little over 3 feet 3 inches – and check which convention a number is using before you compare it with another plan.

The two dimensioning conventions can make a real difference to what you think you are getting. Suppose a bedroom’s dimension line reads 11′6″ × 10′0″ on the outside of the wall – a centre-line figure, giving 115 sq ft. A second, smaller pair of numbers inside the same line, a common way of showing both together, reads 10′9″ × 9′6″, the clear internal size: 102.1 sq ft. That is a difference of 12.9 sq ft, or about 11% of the larger figure, on the same wall, on the same plan. Read the smaller number: it is the one that tells you how much floor you actually get.

What RERA’s carpet excludes

Every unit in a Karnataka RERA filing, and every agreement for sale, states a carpet area – and it is smaller than what the plan’s own outer wall line would suggest, by design. Section 2(k) of the Real Estate (Regulation and Development) Act, 2016 defines it precisely: “‘carpet area’ means the net usable floor area of an apartment, excluding the area covered by the external walls, areas under services shafts, exclusive balcony or verandah area and exclusive open terrace area, but includes the area covered by the internal partition walls of the apartment.”

In plan terms: draw a line around the inside face of every wall enclosing your flat, subtract any shaft the plan shows, and exclude the balcony and any open terrace even where it is marked as yours alone to use. What is left is carpet area. The definition also explicitly includes the internal partition walls inside your flat – the walls between your own rooms count towards it, even though you cannot put furniture on top of them.

That is why the same flat carries a larger number on the brochure. A developer’s own saleable, or super built-up, figure typically adds back the external wall, a share of the common areas outside your front door, and sometimes the balcony. None of that is wrong on its own terms – a promoter may sell on whichever figure it likes, as long as the RERA carpet area is also disclosed – but it will not match a floor plan’s own outer dimension. For how large that gap typically runs, and how to compare two flats on carpet rather than on the brochure figure, see our guide to carpet area vs super built-up.

Comparing room sizes

A brochure plan is drawn to sell the flat, and the easiest way to make a room look larger is to draw the furniture inside it smaller than it really is. A bed shown at four feet wide on a plan that lists a queen-size bed is misdrawing the bed, not the room – but it makes the room around it look roomier by comparison. The safest check is to ignore the furniture and read the dimension lines and the stated area instead. If a room carries no dimension line at all, treat that as a reason to ask for one, not as evidence the room is generous.

When you compare two units – two configurations in the same project, or two flats from different developers – compare like with like. Match the dimensioning convention, internal or centre-line, from the section above. Match the unit, feet-inches or metres. And compare the stated area, not just the shape on the page: a long, narrow room and a square room can carry the same area but feel very different once furnished. Where a plan gives no individual room areas, work them out yourself from the dimension lines before you compare; a total carpet area for the whole flat is not enough on its own to judge one room against another.

Doors, windows and daylight

A door’s swing arc tells you two things before you buy: which way it opens, and how much clear floor it needs while doing so. A door that swings into a small room can rule out a wardrobe or a bed in the corner it sweeps across; a door that swings outward, into a passage, avoids that but can block the passage instead when it is open. Check the direction and the arc on every room’s plan, not just the front door’s.

Windows and ventilation are set by rule, not taste. Karnataka’s building bye-laws require every habitable room to have openings – windows, ventilators or a glazed door – to the outside or to an open verandah, with a minimum combined opening area of one-sixth of the room’s floor area, increased by 25% for a kitchen, and with no part of the room more than 7.5 m from that opening. On the smallest habitable room the bye-laws allow, 9.5 sq m (about 102 sq ft), that one-sixth rule works out to at least 1.58 sq m, or about 17 sq ft, of openable window and ventilator between them.

The same bye-laws set minimum sizes for the rooms themselves. None of this is aspirational: it is the floor below which a room cannot legally be sanctioned.

A plan that shows a room smaller than these figures, or a door-and-window arrangement that does not add up to the minimum opening, has either miscalculated or is not the plan that was actually sanctioned. Either way, it is worth a direct question to the promoter before you sign anything.

Shafts, ducts and columns

A shaft and a column look similar on a plan – both are small, fixed boxes – but they do different jobs, and neither one moves. A structural column carries the load of the floors above; it sits inside or against a wall, usually repeating in the same spot on every floor of the building, and no renovation can relocate it. A shaft is a vertical duct running the full height of the building for plumbing stacks, electrical risers or ventilation; it too repeats, floor to floor, in the same position, because every floor’s pipes have to line up with the one above and below.

Both eat into a room’s usable floor in a way the wider carpet-area figure does not always make obvious at a glance: a shaft is explicitly excluded from carpet area under RERA’s own definition, so a room with a shaft box drawn inside it is smaller to live in than its stated area alone would suggest. Look for these boxes on every room you plan to furnish, not only the ones near the kitchen and bathrooms where they are most common, and ask what each one carries if it is not obvious from the plan.

Balconies and utility areas

A balcony is drawn outside the main wall line, and how it is treated depends on what kind it is. Under RERA’s definition, an exclusive balcony or verandah – one that belongs to your flat alone – is specifically excluded from carpet area, even though it is yours to use and is very likely priced into what you pay. A shared or common balcony is not part of your flat’s carpet area either; it may instead be counted, at a fraction, into whatever produces the developer’s super built-up figure.

A utility area – usually a small enclosed space off the kitchen for a washing machine, plumbing points or a wet-waste bin – is generally treated as ordinary carpet area if it sits inside your flat’s own walls, the same way a store room would be. Check the plan’s own labelling and, where you can, the unit’s entry in the RERA filing, rather than assuming: promoters do not always use the same label for the same kind of space, and a “utility” on one project’s plan can be a different thing – sometimes carpet, sometimes an open deck – on another’s.

Find the north arrow

Every plan carries a north arrow somewhere on the sheet, usually a small symbol near a corner or the title block. It is easy to miss, and easy to misread if the plan has been rotated for a tidier layout on the page – the top of the drawing is not always north. Once you have found it, you know which way each room’s windows actually face, and can work out how the sun moves across the flat through the day, which rooms get the harsh afternoon sun and which stay shaded, and what fire, lift and setback rules apply at that floor. All of that is covered in our guide to choosing floor, facing and unit; this guide’s job is only to get you to the arrow itself, correctly, before you use it.

Which plan are you looking at

Typical floor vs your unit

A typical floor plan shows one full storey of the building: every unit on it, the staircase, the lifts, the shafts and the corridor between them. Your own unit plan is a close-up of just your flat, usually drawn larger and with more dimension detail. Ask for both. The typical floor plan is what tells you whether a neighbour’s kitchen backs onto your bedroom wall, where lift-lobby noise will come from, and whether the unit beside yours is a mirror image of your own or something different in size and shape – none of which a single unit’s plan can show you on its own.

Brochure plan vs the sanctioned plan

The brochure plan handed to you at a sales office is marketing material, drawn, or redrawn, to look clean and to fit a page. The sanctioned plan is the one the planning authority actually approved, stamped and on file, and it is the one construction is legally required to follow. Our guide to documents to check before you buy covers what a sanctioned plan itself is and where it fits among the rest of the paperwork; this section is only about comparing the two plans against each other.

The two should match. In practice, minor differences creep in – a wall moved a few inches for the show flat, a balcony enclosed after sanction, a room re-labelled from what the authority approved – and the only way to know your unit matches what was actually sanctioned is to compare them directly, room by room.

Before you sign off on a plan

• Confirm the scale and the dimension convention – internal or centre-line, feet-inches or metres – before comparing any two numbers.
• Match the brochure plan against the sanctioned plan, room by room, not just at a glance.
• Ask for the typical floor plan, not only your own unit’s, so you can see what sits beside and above you.
• Locate every shaft and column on the rooms you plan to furnish, and ask what each one carries.
• Check the north arrow before judging any room’s light or heat.
• Work out each room’s own area from its dimension lines if the plan does not state one.
• Compare the plan’s carpet area against the figure in the RERA filing and your agreement for sale.