What do I do if the official floor area for my property is wrong?
First: check whether the difference is simply the walls. Most "wrong record" cases turn out to be two different ways of measuring. If something is still left over afterwards, it's the owner's job to get it corrected — through whichever authority keeps the record.
Short answer: start by ruling out the ordinary explanation — a registered floor area is usually measured externally, you measure internally, and the difference is the walls, typically 15–20% of the registered figure. If the walls can't explain the gap, it's generally the owner who's responsible for making sure the record is correct, and the correction happens through whichever authority keeps it — a land registry, a local council or a county office, depending on where the property is. Never correct an area on a hunch: measure it room by room first, so you have a figure and a drawing to bring with you.
Is the record actually wrong?
Most "errors in the record" aren't errors at all. They're two different ways of measuring, and both can be correct at the same time.
A registered floor area is usually measured to the outside of the exterior walls, with internal partitions counted in. When you walk round with a tape measure yourself, you measure wall to wall, and every wall drops out of the sum.
Work out the difference before you do anything else. The rule of thumb: the exterior walls take up roughly the wall thickness times the house's perimeter.
- House measuring 8 × 12 m externally → perimeter 40 m, registered area 96 m² (about 1,030 sq ft).
- Exterior wall 35 cm thick, measured at a window reveal from the inner face to the outer face.
- 40 × 0.35 = 14 m² in exterior walls — the rule counts the corners twice, so the true figure is 13.5 m².
- Internal partitions typically add another 2–4 m² on top.
- The walls therefore account for 15.5–17.5 m².
The record says 96 m². Your own floor measurement says 79 m². The gap is 17 m², and that sits right in the middle of the range the walls explain. There's no error. There's a house.
Find out what's actually on the record
Pull up the record for your address and read it line by line. Living area, footprint, total building area, basement area, converted attic, sunroom area and carport are separate fields. A surprisingly large share of "errors" people find turn out to be a floor measurement compared against the wrong field.
Look especially for something registered wrong in kind rather than in number:
- A sunroom or a covered area that's ended up inside the living area — or the other way round.
- A basement listed as habitable space that isn't actually fitted out for it.
- An attic listed as converted, even though no floor was ever laid.
- An extension from a decade ago that nobody ever reported.
- A heating system or water supply that was replaced long ago and never updated on file.
The fields that aren't about area are often the easiest to get corrected, and they matter just as much: they're used by insurance, by property valuations, and by whoever buys the home one day.
Measure it, so you have something to bring
An authority can't correct an area because you feel it's wrong. You need to bring evidence. It doesn't need to be sophisticated — it needs to be verifiable.
Measure room by room. In each room: length and width at floor level, taken in two places in each direction, since walls in older houses are rarely parallel. Note alcoves, chimney breasts and other projections separately. Add the rooms' areas together, and also note the exterior wall thicknesses you measured at the windows — that's the figure that translates your internal number into the record's external one.
Write the measurements onto a sketch with the rooms drawn in. A drawing with figures on it says in one second what three paragraphs of text can't.
HouseSense produces that sketch for you: scan the home with your iPhone's LiDAR, or draw it by hand on graph paper with your finger. You get a measured floor plan with area per room and in total, which you can export as a PDF. The areas are internal, wall to wall — so remember it's that figure that needs translating into the record's external one, not the other way round.
Who corrects the record?
The record is kept by a public authority — a land registry, a council or a county office, depending on the country. That authority registers, amends and approves the information, and it's therefore who you need to contact. As a general rule it's the owner who's responsible for making sure the information about the property is correct and up to date. That includes information that was registered wrong long before you bought the house.
Some fields the owner can report themselves through a self-service system; others require case handling, and a few changes require a building permit behind them first. Exactly which fields belong to which category changes over time and isn't something you should guess at.
The cheapest minute in the whole process is therefore the phone call: ask the authority what they need before you spend a weekend measuring the wrong thing. Most will happily answer that exact question, and the answer is often that nothing more is required than your own report.
What does it cost to get an area corrected?
Correcting an entry on the record itself is usually not something you pay for. What can cost money is whatever sometimes has to happen before the correction can go through — and that's the question you need answered first.
If the authority requires a survey from a licensed surveyor, or something needs to be formally approved through a building permit, you're looking at a professional service and possibly a case fee — a bill that can range from modest to substantial, depending on the property and how much surveying and drawing is needed. If, on the other hand, the authority requires nothing beyond your own report, it costs nothing at all. The gap between those two outcomes is the whole difference, and you can clear it up with a single phone call before you commission anyone.
What a wrong area means in practice
A wrongly registered area isn't just a number on paper. It follows the property:
- Property valuation and tax are based on the registered information. Too many square metres on file and you can end up paying too much; too few and a correction can catch up with you later.
- Insurance often calculates the sum insured and the premium from the area. A registered area that's too low can, in the worst case, mean the property is underinsured.
- At a sale, the listing needs to be built on solid ground. A buyer who measures and finds fewer square metres than advertised has grounds for a complaint — and that's a position no seller wants to be in.
- At a renovation, the authority starts from what's on the record. If the record is wrong, the permit application starts off crooked, and that mistake is more expensive to fix midway through a project than before it.
What you shouldn't do
Don't report an area you've worked out by multiplying your internal measurement by some percentage you found online. The relationship between internal and external area depends on your house's perimeter and your wall thicknesses. Two houses of 80 m² externally lose different amounts to their walls: a square house measuring 8.94 × 8.94 m loses 12.0 m², while a long, narrow house measuring 5 × 16 m loses 14.2 m² — over two square metres apart at exactly the same external area.
And don't guess at the rules for sloped ceilings, basements and sunrooms. Those are the three places where the technical definitions decide everything, and where a qualified guess turns into a wrong report with your name on it. Measure what you can measure — ceiling heights, floor areas, wall thicknesses — and let the authority decide how it should be registered. That's what it's there for.