How Istanbul's Building Stock Ended Up Full of Duplicate Records — and Why Fixing It Matters Now

Istanbul's land registry has a problem it has been accumulating since the 1970s: an unknown but substantial number of properties appear more than once in municipal and national databases, the result of repeated, overlapping digitisation drives that never fully reconciled analogue-era cadastral maps with their electronic successors. The Istanbul Metropolitan Municipality's GIS directorate acknowledged the scale of the challenge in internal working documents circulated during the 2024 urban-renewal push in Fikirtepe, a dense neighbourhood in Kadıköy district where compulsory purchase orders stalled for months partly because title searches returned conflicting records for the same parcels.

The timing is not incidental. After the February 2023 Kahramanmaraş earthquakes killed more than 50,000 people across southern Turkey, the government accelerated its urban-transformation programme under Law 6306, the statute that empowers authorities to demolish and rebuild risky structures. That acceleration exposed just how unreliable the underlying data is. Contractors bidding for demolition work in Bağcılar and Sultangazi — two western districts flagged by Istanbul University's earthquake engineering studies as high-risk — reported receiving site plans that duplicated entire apartment blocks, assigning two legal identities to a single seven-storey building.

How the Duplication Grew

The roots go back to at least three separate digitisation campaigns. Turkey's General Directorate of Land Registry and Cadastre, known by its Turkish acronym TKGM, ran a nationwide mapping project through the 1980s and 1990s that converted paper parcel maps into vector files. Istanbul, with its roughly 39 districts and more than 15 million residents, was processed in batches, often by different contractors working to slightly different coordinate reference standards. When the municipality launched its own digital mapping initiative in the early 2000s — later consolidated into what is now the IBB's e-Kent infrastructure — the two datasets were merged without a systematic deduplication step. A third layer arrived after 2012, when TKGM began issuing electronically signed title deeds that pulled property identifiers from both legacy systems simultaneously.

The Fatih district, which contains the historic peninsula and some of Istanbul's oldest building stock, illustrates the cumulative effect. Fatih has approximately 70,000 registered parcels according to figures TKGM published in its 2022 annual report, yet municipal planning files for the same area reference a higher count because boundary adjustments made during the 2008 district reorganisation were logged separately rather than merged into the master record. Insurance companies pricing earthquake coverage across the city have flagged the discrepancy to the Turkish Insurance Association, arguing that premium models cannot be calibrated accurately when the denominator — the total number of distinct insurable structures — is itself uncertain.

What Needs to Happen Next

The practical fix requires a process called duplicate image replacement at the database level: identifying records that share physical coordinates or parcel geometry within a defined tolerance, flagging them for human review, and retiring the redundant entry while preserving its audit trail. TKGM has piloted exactly this approach in Ankara's Çankaya district, completing a reconciliation of roughly 12,000 parcels between January and April 2025 according to the directorate's quarterly progress bulletin. Istanbul, with a land registry roughly ten times that size in the affected zones alone, presents a different order of difficulty.

For property owners in areas like Zeytinburnu or Gaziosmanpaşa — both prioritised under the government's urban-transformation schedule — the duplicate problem has immediate financial consequences. A property appearing twice in the register can be subject to two separate lien searches, two sets of administrative fees, and in at least some documented cases, two competing compulsory purchase valuations. The Istanbul Bar Association's property law committee has been advising clients to request a full parcel history printout from the nearest TKGM branch before signing any urban-transformation agreement, a step that takes roughly two weeks and costs 450 lira at current fee schedules.

The municipality and TKGM have both indicated, in separate planning documents, that a unified deduplication project for Istanbul is scheduled to begin in the second half of 2026. Whether the budget allocation survives the current fiscal pressure on local government — the lira's depreciation has pushed municipal borrowing costs sharply higher over the past 18 months — will determine how quickly residents in high-risk districts can be confident the paperwork matches the building standing in front of them.