You should be very careful while buying construction materials. You have to do perfect planning before you purchase the materials. Poor quality materials can lead to disasters. It will also make you suffer from huge loss while constructing or after. Managing the materials is not required only during the stage of monitoring. Decisions are required to be made during the stages of scheduling and planning.
You have plan the purchase of the materials. This decision cannot be taken by anybody. It requires an experienced and qualified person. This expertise person would take the scope of the work into account. Next, he will take your choices into account. Along with that he will follow the laws of building. This planning will always follow a critical path. Hence, materials would be purchased according to the need. The materials purchased should match the standard of the quality defined by building laws.