BBR data in property development: what it shows — and where it's wrong

The Danish Building and Dwelling Register (BBR) is often the first place you look up a property. It’s free, public and covers virtually the whole of Denmark’s building stock. But BBR has a weakness that costs developers dearly if they overlook it: a large share of the information is reported by the owners themselves and is not systematically verified. The data can therefore be out of date, incomplete or simply wrong.

This article covers what BBR reliably tells you, where it typically fails, and how to cross-check it before you run the numbers on a site.

What BBR contains

BBR describes the physical characteristics of sites, buildings, units (homes and commercial premises) and technical installations. The most-used fields in a development context are:

• Built area and total residential area per building and unit.
• Year of construction and any year of conversion or extension.
• Number of storeys and use of the attic.
• Use code — e.g. detached single-family house, terraced house, apartment building, commercial.
• Heating installation, drainage, external wall and roof material.
• Number of rooms, toilets and bathing facilities per unit.

Used correctly, it gives a quick picture of what stands on the site today — and therefore a starting point for assessing what can be demolished, converted or extended.

Where BBR typically goes wrong

1. Areas not updated after a conversion

An extended roof, a converted basement or an extension that was never registered means the real area differs from BBR. It goes both ways: some properties are larger than registered (unreported use), others smaller (demolished without deregistration).

2. Wrong or missing use code

The use code drives everything from property taxation to what can be lent against. A former commercial property used for housing without a changed code — or vice versa — is a classic source of error.

3. “Illegal” or unregistered square metres

If BBR shows fewer m² than reality, it may be due to construction without a building permit. That’s not just a registration problem: it can become a legalisation case that the buyer inherits.

4. A construction year that hides a thorough renovation

A construction year of 1950 tells you nothing about a 2019 deep renovation. Use the conversion/extension-year field alongside the construction year.

How to cross-check BBR

BBR should never stand alone. The strongest cross-checks are all public:

• The cadastre (Geodatastyrelsen) for the site’s real area and boundaries — the floor area ratio is calculated on the cadastral area, not on BBR.
• Aerial and oblique photography to see whether the building footprint in the image matches the registered areas.
• The land register for easements and encumbrances that can constrain use independently of BBR.
• Plandata.dk for the local plan and municipal framework that decide what the areas may be used for.
• The municipal building-case archive to verify that conversions and extensions actually have permits.

When those sources point the same way, you can trust BBR. When they disagree, you’ve found a risk to clear before the deal.

BBR errors aren’t only a risk — they’re an opportunity

Every discrepancy is either a problem to deduct from the price, or a potential no one else has spotted. A site with unused development rights, a mis-coded use that can be reclassified, or a registered area lower than the physical one — these are exactly the gaps a thorough screening finds, and they decide whether a deal is a good one.

From raw data to a single picture

The problem with BBR is rarely that the information is hard to find — it’s that it has to be compared with five other registers before it means anything. That assembly is what Arcili builds: cadastre, BBR, land register, local plan and photography on one screen, so the discrepancies jump out instead of hiding between tabs.

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