How São Paulo's Housing Crisis Turned Duplicate Image Data Into a Policy Battleground

City Hall's Secretaria Municipal de Habitação confirmed last month that duplicate cadastral images — the same property photographs filed under multiple registration numbers in São Paulo's official housing database — now affect an estimated 340,000 records across the municipal system. The problem did not appear overnight. It accumulated over roughly two decades of rushed digitisation, competing data-entry contracts, and administrative handoffs between successive city governments.

The timing matters. Ricardo Nunes's administration is midway through its second term and under pressure to demonstrate measurable progress on the city's chronic informal housing problem before the 2026 municipal budget cycle closes in October. Duplicate image records slow every downstream process: eviction appeals, regularisation certificates, infrastructure investment allocation, and the federal Minha Casa Minha Vida programme's local verification checks. When a property image is filed twice under different matriculation codes, the system flags a conflict and a human reviewer must intervene. In a city with a documented housing deficit of 474,000 units — a figure published in the 2023 Fundação João Pinheiro housing survey — every processing delay has real consequences for families on waiting lists.

How the Files Got This Way

The roots of the duplication problem trace back to 2003 and 2004, when the Prefeitura de São Paulo began converting paper property files into digital records under a programme called Geosampa, the city's official geographic information platform. Field teams photographed properties across districts including Brasilândia, in the northern Zona Norte, and Cidade Tiradentes, on the far eastern edge of the city. Both areas were priority zones for informal settlement regularisation. The contractors hired to upload those images worked under separate purchase orders and used incompatible file-naming protocols. Photographs were frequently uploaded more than once — sometimes by different teams photographing the same street block, sometimes because a reviewer assumed a file had been lost and ordered a re-upload.

The problem compounded after 2013, when the city migrated to a newer cadastral platform and attempted to merge legacy files automatically. The merge algorithm matched records by address string rather than by a unique property identifier. In dense neighbourhoods like Heliópolis, near the Sacomã district in the south, streets with abbreviated names in old records and full names in new records generated thousands of mismatches. Each mismatch produced a duplicated image entry rather than a corrected single record. Instituto Pereira Passos, the city's data and statistics agency, flagged the problem internally in a 2019 technical audit, but the correction project was never funded through the regular budget cycle.

What a Fix Actually Requires

Correcting the records is not simply a matter of deleting extra files. Each duplicate image is legally attached to a cadastral entry, and that entry may have been cited in court documents, loan applications, or regularisation certificates. Removing an image without cross-checking its legal dependencies risks invalidating a chain of documentation that a family may have relied on for years. The Secretaria Municipal de Urbanismo e Licenciamento, which handles building permits, and the Secretaria de Habitação, which manages social housing, must coordinate on any correction — two agencies with separate IT systems and separate budget lines.

A corrective project proposed by the Nunes administration in early 2025 estimated a cost of R$ 18 million over 18 months to audit, deduplicate, and legally validate the affected records. That proposal is currently sitting with the Câmara Municipal's housing committee. Civil society groups based in Pinheiros, including Movimento Defenda São Paulo, have pushed for the project to include community-level data verification in affected favelas rather than relying solely on algorithmic deduplication — arguing that an automated pass will replicate the original errors in a new format.

For residents and urban planners, the practical next step is pressure on the committee to approve the budget line before October. Families in regularisation queues in Paraisópolis and Jardim Ângela whose files carry duplicate image flags can contact the Secretaria de Habitação's district offices directly to request a manual review — a slower process, but one that bypasses the automated conflict hold. The deeper question is whether City Hall will treat the deduplication project as a one-time correction or finally build a unified property image registry with enforceable filing standards, so the same chaos does not regenerate itself with the next system migration.