House is the third topmost need of individuals next to food and clothing. The production of this essential human shelter is in deficit in Nigeria. The managing director of the Federal Mortgage Bank of Nigeria (FMBN) reported recently that the housing deficit in Nigeria is 22 million units. Despite numerous government policies and housing reform programmes, housing remains an illusion to an average Nigerian. The solution to this generic problem is a production of mass housing through the use of affordable local materials and interlocking brick is one of such materials. The study compared the cost of producing mass housing using conventional (sandcrete) blocks and interlocking bricks as walling material. A prototype building plan of a three-bedroom apartment was used for the analysis using percentile. Historical costs data were collected from specialist interlocking bricks manufacturer while costs data on conventional blocks and labour were collected through a market survey. The result also indicates that the labour cost for the conventional block was ₦1,025.64/m2 while the labour cost for the interlocking block was ₦1,709.40/m2. The overall cost for the conventional block was ₦17,782.19/m2 while the overall cost for interlocking brick was ₦10, 378.06/m2. This implies that there is a 58% cost saving in using interlocking bricks. The study recommended that the government should encourage the use of interlocking bricks for affordable mass housing in Nigeria because of its several advantages such cost-effectiveness, reduced construction time and easy access to the raw materials from the local environment. The study recommended that a regulatory body should be set up to implement compliance with the standard specified by the Nigerian Standard Organisation, to ensure production of quality interlocking bricks for mass housing in Nigeria.Â