How Berlin's Housing Databases Ended Up Drowning in Duplicate Images — and What's Being Done to Fix It

Berlin's housing administration has a problem it rarely advertises. Across the Senatsverwaltung für Stadtentwicklung, Bauen und Wohnen and the network of twelve Bezirksämter that feed data into central planning registers, duplicate image files have accumulated over more than a decade of piecemeal digitalisation. Staff processing building permits and rental-registry updates in offices from Marzahn to Tempelhof routinely encounter the same floor-plan scans, facade photographs and inspection certificates filed under multiple reference numbers, clogging workflows and inflating storage costs.

The problem did not arrive overnight. It is the direct product of how Berlin chose — and, critically, how it failed — to modernise its records infrastructure between roughly 2012 and 2024.

A Decade of Half-Finished Digitalisation

When the city launched the FIS-Broker spatial information platform as a public-facing layer over its geographic data, the back-end document stores were never fully unified. Each Bezirksamt retained its own scanning unit and its own naming conventions. A fire-safety inspection photograph taken at a Neukölln apartment block on Hermannstraße in 2017, for instance, might be uploaded by the local Bauaufsichtsamt, then re-uploaded when the same file was attached to a separate Mängelrüge filed six months later, then again when the block's entry migrated to the citywide WoR — the Wohnraumregister — after its partial launch in 2023. Nobody built a deduplication step into any of those handoffs.

The Wohnraumregister itself, mandated under Berlin's Wohnraumversorgungsgesetz and overseen by the Investitionsbank Berlin, was supposed to create a single authoritative record for every rental unit in the city. When rollout began, administrators discovered that importing legacy document packages from the Bezirksämter produced image-duplication rates that internal working papers, shared with council members in late 2024, described as substantial — though the city has not published a precise figure. Housing committee members across the SPD-led coalition have since raised the issue in Abgeordnetenhaus sessions, pointing to the drag on approval times for new rental listings and Milieuschutz assessments in protected neighbourhoods like Prenzlauer Berg and Kreuzberg.

Storage is not a trivial cost. Government cloud contracts in Germany, typically procured through framework agreements administered by the Bundesamt für Sicherheit in der Informationstechnik, price object storage by the terabyte per month. Redundant image files multiplied across twelve borough systems add up. A 2024 audit by the Berliner Rechnungshof — the city's independent financial watchdog — flagged inefficiencies in digital-document management across several Senate departments, though the housing-specific duplication issue was noted as part of broader findings rather than named as a standalone line item.

Where the Fix Stands Today

Since January 2026, the Senatsverwaltung has been piloting an automated deduplication pipeline developed in partnership with the city-owned IT service provider ITDZ Berlin. The tool uses perceptual hashing to match visually identical images regardless of filename or file path, then flags them for human review before deletion. The pilot ran first on document batches from Friedrichshain-Kreuzberg, chosen partly because that borough has one of the city's highest concentrations of Milieuschutz zones and therefore one of the heaviest documentation loads.

The broader rollout, scheduled to cover all twelve boroughs by the end of the third quarter of 2026, will feed cleaned image sets back into the Wohnraumregister. Officials working on the project have indicated — without specifying figures — that the cleaner database should reduce average processing time for new rental-unit registrations. That matters directly to renters and landlords navigating Berlin's rent-cap framework, where delays in registration can hold up legally required Mietspiegel assessments.

For residents dealing with the housing administration, the practical takeaway is straightforward: applications tied to properties in the pilot boroughs may already be moving faster through the system. Anyone with a pending Milieuschutz inquiry or a new rental-contract registration involving a Friedrichshain-Kreuzberg address can contact the relevant Bezirksamt directly to check whether their file has been processed under the cleaned registry. The ITDZ Berlin maintains a public-facing status page for the Wohnraumregister at the Rotes Rathaus service portal, updated monthly.