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Evaluation of sites’ material wastages is crucial for its minimization. It has been opined that estimators’ allowances for materials on construction sites are inadequate. This study therefore compares sites’ waste quantity of selected materials with the estimators’ allowances. The selected materials are concrete, blocks, tiles, aluminium profiles and glass. The objectives are to evaluate the waste quantity of selected materials on sites, to establish their estimators’ allowances and develop models that can be used to predict the waste quantity of the selected materials on projects. The study area was Lagos state, Nigeria.  Site measurement was used to evaluate the site waste generation of the selected materials, while the estimators were asked for their allowances. The projects used for the study were identified by purposive sampling technique. A total of 97 projects under construction were used for the study. Data were analyzed using mean, frequency, percentage, t-test and factor analysis, while regression analysis was used for the development of models. The study reveals that estimators allowance for material waste ranges between 8.36% and 10.06% contrary to the current opinion of 5% and glass showed the greatest level of underestimation by estimators. It is concluded that glass has the highest wastage quantity on building sites while the least is aluminium profiles. It is recommended that the site waste quantity determined in this study should be used as benchmarks for the materials. The waste models should also be used to predict waste quantity of the materials on projects, so as to make adequate provision for them before construction commences.
Keywords: Allowances, estimators, models, sites, waste quantity.