Non-usable floor area areas in the brief need to be supplemented with an estimate of the non-usable areas (i.e. = areas for construction elements, technical services and circulation).Gross \x0foor areaGross floor areax Estimating construction costsTo get an idea of the total construction Construction costs / sq.m. costs, the projects gross floor area can be multiplied by an average unit cost = (construction costs per square metre). Total construction costsTotal construction costs+ Estimating total costsThe costs of a project are not limited to Other project costs construction costs alone. To arrive at the total costs, expenditure for fees, insurance, = taxation, permits and relocation also have to be included. Total investment costsBasic calculation stepsThe first step in making a cost estimate is to define the size of the project. For this, the usable areas, as specified in the brief, need to be supplemented with non-usable areas (areas needed for circulation, walls, shafts, HVAC). Together these make up the gross floor area, which is the area that actually needs to be constructed. This figure can then be multiplied by a unit cost for the construction of the building. The trick here is to use a cost figure that is truly relevant to the building (looking at things like size, shape, location, quality level).This gives the total construction costs, to which additional project costs (i.e. design fees, taxes, insurance costs, relocation costs) have to be added to arrive at the total required investment.