Assessment of Green Roof Feasibility in High-Density Urban Areas of Lagos State

Green roofs offer multiple urban benefits including stormwater management, thermal insulation, and biodiversity enhancement, and their feasibility in the high-density urban context of Lagos State, South West Nigeria, is an emerging area of professional interest. This study assessed the technical feasibility, economic viability, and regulatory context for green roof adoption in high-density residential and commercial areas of Lagos Island, Mainland, and Victoria Island. A desk study combining structural load analysis, rainfall data assessment, and green roof system cost-benefit analysis was conducted. Site surveys of 40 rooftop spaces in the study areas assessed structural capacity, sun exposure, and access conditions. Interviews with 25 architects, engineers, and estate developers explored professional interest and perceived barriers. Results showed that 45% of surveyed rooftop spaces met minimum structural load requirements for lightweight green roof systems (minimum 1.5 kN/m2 additional load capacity) without retrofit. Annual stormwater runoff reduction potential per green roof installation was estimated at 40 to 65% based on Lagos mean annual rainfall of 1,832mm. The 20-year lifecycle cost-benefit ratio was positive (ratio: 1.34) when energy savings and stormwater management benefits were monetised. Regulatory guidance on green roofs was absent in Lagos State Building Regulations, identified by 88% of respondents as the primary adoption barrier. The study recommends the inclusion of green roof guidelines in the revised Lagos State Building Control Regulations.

Keywords: green roof, urban sustainability, Lagos State, stormwater management, building regulations