Structural Evaluation of Colonial-Era Masonry Church Buildings in Abeokuta, Ogun State

Colonial-era masonry church buildings in Abeokuta, Ogun State in the South West geopolitical zone, represent some of the earliest surviving examples of institutional architecture in Nigeria and face increasing structural vulnerability due to their age, material degradation, and changing use patterns. This study evaluates the structural condition of six masonry church buildings constructed between 1846 and 1920 in Abeokuta, documenting defects, assessing residual structural capacity, and identifying interventions required to extend their service life. The assessment methodology combined visual inspection, mortar sampling for carbonation and compressive strength testing, crack mapping, and ground-penetrating radar surveys to characterise foundation geometry and subsurface conditions. Structural adequacy under self-weight, wind loading, and roof-imposed loads was evaluated using simplified masonry analysis procedures consistent with Eurocode 6. Results indicate that all six buildings exhibited moderate to significant levels of mortar deterioration, with compressive strengths averaging 0.8 N/mm2, below the minimum of 2.5 N/mm2 typically required for load-bearing lime mortar masonry. Cracks attributable to foundation movement were identified in four buildings, with two showing active settlement as indicated by crack monitoring over a six-month period. The study recommends a phased conservation programme incorporating repointing with compatible lime mortar, underpinning of the most critically settled foundations, and roof structure replacement for buildings where original timber members have lost structural section. A heritage overlay designation is advocated to protect these buildings from incompatible alterations. Keywords: masonry church buildings, structural evaluation, Abeokuta, heritage conservation, colonial architecture.