Evaluation of Load-Bearing Capacity of Timber Roof Trusses in Residential Buildings in Enugu State

Timber roof trusses remain a widely adopted structural system in low-rise residential construction across South East Nigeria, yet formal evaluation of their load-bearing capacity under local conditions is rarely conducted. This study evaluates the structural performance of timber roof trusses in selected residential buildings in Enugu State, examining the influence of timber species, joint configurations, member sizing, and construction quality on overall truss behaviour. A field survey of forty residential buildings constructed within the last fifteen years was conducted, supplemented by laboratory testing of timber samples to determine bending strength, modulus of elasticity, and moisture content. Structural analysis was performed using limit state design principles in accordance with BS 5268 and the Nigerian Standard for Structural Use of Timber. Results indicate that a significant proportion of the surveyed trusses were under-designed relative to the imposed roof loads, with nail-plate joints showing inadequate shear resistance in over half of the sampled connections. Moisture content in harvested timber samples frequently exceeded the recommended threshold of eighteen percent, increasing the risk of creep failure and fungal degradation over time. The study identifies a critical need for standardised timber grading and joint design guidelines applicable to locally available species such as Iroko and Opepe. Recommendations include mandatory structural certification of roof truss designs prior to construction approval and training of local carpenters on best-practice jointing techniques. Keywords: timber trusses, load-bearing capacity, Enugu State, joint design, residential construction.