C‑DRONE
Drone flying close to a building facade for inspection

C-DRONE GUIDE · 30 JULY 2026

Social housing stock audit by drone: roofs, façades, price

A social landlord manages tens of thousands of dwellings across hundreds of buildings, and must constantly arbitrate: which estates to refurbish first, on what budgets, on what evidence. Regulation has tightened the exercise — G-rated dwellings banned from rental since 2025, F in 2028, E in 2034 under the Climate and Resilience law, mandatory multi-year plans — while the 1960s–1980s stock ages faster than budgets grow. In that vice, objective knowledge of envelope condition — roofs, façades, waterproofing — becomes strategic. A portfolio-scale drone campaign provides it within weeks, with no scaffolding or lift at the foot of occupied buildings. Method and prices observed in 2026.

Published on 30 July 2026, reviewed on 1 August 2026 — regulations in force as of August 2026.

Social housing stock: large, homogeneous, poorly known up high

French social housing has a feature precious for an aerial campaign: its homogeneity. Whole generations of estates share the same construction methods — flat roofs with multilayer waterproofing, precast panel façades, rendered gables — hence the same pathologies at the same ages. Yet sampling is not enough: exposure, past maintenance and original defects make twin buildings diverge. Every roof and every façade must be seen — which classic surveys, done from the ground and from dwellings, never truly cover.

The need to objectify a large stock's condition to plan its renovation is not new: as early as 2000 the European EPIQR method, presented by Flourentzou, Droutsa and Wittchen in Energy and Buildings, formalised the assessment of residential building degradation as the basis for refurbishment scenarios (see the study on Google Scholar). The drone supplies such methods with what they always lacked: exhaustive, dated data on the upper parts.

The campaign: dozens of estates in a few weeks

The campaign is planned like a tour: estates grouped by sector, three to six sites a day depending on size, prior tenant information by notices — non-negotiable on occupied sites — and flights within the built-up area framework, without overflying people. Per building, the protocol is standard: photographic passes over each roof slope or terrace, façades and gables in vertical ascents, zooms on singular points — parapets, panel joints, balconies, concrete canopies.

The images feed a consistent rating grid: every roof and façade scored, every defect located and qualified — panel cracking, spalling reinforced concrete, render debonding, end-of-life waterproofing, vegetated gutters. On façades, the reading is that of our façade diagnosis before renovation guide; on safety, it also documents falling-material risk, the owner's first liability. The campaign logic matches the school roof audit: pooling to slash unit cost.

The thermal module: crossing envelope and EPC

Rental bans trigger on the EPC — but works are designed on the real envelope. A thermal pass in the heating season crosses the two: slab-edge thermal bridges, panels missing insulation, the actual performance of ageing external insulation, terraces with waterlogged insulation. On E, F or G-rated estates, it separates buildings where insulation comes first from those where joinery or ventilation dominates — and documents gaps between theoretical EPC and the envelope's real behaviour.

The method and its conditions — winter flights, protocol, interpretation limits — are those of our collective EPC and works plan guide, applied here at portfolio scale. On the landlord's hostels, senior residences and office buildings, the module joins the tertiary decree trajectory. Our façade inspection drone page describes the underlying unit service.

From report to asset strategy

The deliverable that justifies the campaign is not the photo library — it is the prioritisation matrix: each estate positioned by envelope condition, energy label and regulatory deadlines, with safety emergencies extracted as a separate list. This matrix feeds directly into the asset strategy, refurbish-or-demolish arbitrations and financing files — where dated photographic findings weigh more than expert opinion.

The campaign also serves day-to-day management: evidence for storm claims, before/after states for refurbishment works acceptance, spotting roofs suited to photovoltaics, and monitoring evolving defects — a panel crack rated in year N is re-compared in year N+2, the monitoring logic that makes repeated campaigns valuable. The data, finally, flows into the landlord's asset information system: every image georeferenced, dated, attached to a building — a documentary asset that outlives the teams.

Prices observed in 2026

Ranges observed in 2026 (excl. VAT):

Campaigns are usefully contracted as multi-year framework agreements, with revisits of sensitive estates. Request a quote stating the number of estates and buildings, their dominant typology and the asset strategy's deadline.

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Put it into practice

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