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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.