Approximate Estimate Numerical (English)

Plinth Area Method / Square Meter Method : In this method, the approximate cost of the proposed structure is calculated on the basis of the plinth area of the building multiplied by the plinth area rate prevalent in the region. The rate for unit plinth area is determined from the cost of a similar building having similar specifications, height, construction procedure, and locality as that of proposed building. The plinth area estimate (PA Estimate) of a building is calculated by finding the plinth area of building and multiplying it by the plinth area rate. Approximate cost = plinth area of proposed structure × plinth area rate. In fixing the plinth area rate, careful observation and necessary inquiries are made in respect of quality and quantity aspects of materials and labor, type of foundation, the height of a building, roof, woodwork, fixtures, number of stories, etc. Plinth area rate = cost of construction/plinth area. The plinth area should be calculated for the covered area by taking the external dimensions of the building at floor level. The courtyard and other open areas should not be included in the plinth area. In multi-storeyed building plinth area rate for each story can be calculated separately. If the plan of building is not ready or available, then total carpet area is calculated as per the proposal requirements and extra 30 to 40% of the carpet area is added for walls, circulation an waste to get the approximate total plinth area. As per IS 3861-1966, areas were included/excluded while calculating the plinth area of the building. Cubical Content Method / Cubic Meter Method : In this the estimate is worked out on the basis of the cubical contents of proposed building to be constructed and then applied to it the rate per cubic meter. This estimate is more accurate than plinth area estimate & service unit method. The local cubic rate is determined from the cost of similar building having similar specifications, height, construction procedure and locality as that of proposed building. This method is generally used for multi-storied buildings. The cost of a structure is calculated approximately as the total cubical contents (Volume of buildings) multiplied by the Local Cubic Rate. The volume of building is obtained by the Length x breadth x depth or height of the building. The length and breadth should be taken as the external dimensions of the building at floor level excluding the plinth offset. The height should be taken from the floor level (i.e. plinth level) to top of the roof (or half of the roof for the sloped roof). In the case of multi-story building, the height should be taken between the floor level of one story to the top of the next higher floor. Based on IS 3861 the foundation and plinth and the parapet above the roof are not taken into account in finding cubical content. Unit rate / Unit base / Service Unit method : This technique is used for preparing preliminary estimates(i.e. order-of-magnitude type estimate) This estimate is generally prepared during the conceptual planning phase of a project, with little information available with the estimator. In this method, the total estimate of cost is limited to a single factor. Each building is constructed to serve some purpose e.g., hospital is designed to accommodate certain no. of beds, the hostel is designed to accommodate a certain no. of students. This purpose is considered as a service unit, a single factor to calculate the cost of building. The approximate cost is calculated by multiplying the cost per unit factor by the number of units of the corresponding factor. The details of the unit cost of different factors can be obtained from records of past projects. The ‘per unit factor' obtained from past similar projects can be adjusted by taking into account different parameters namely the location and size of the project, prevailing market conditions, etc. The accuracy of this technique depends on the quality and reliability of the data available with the estimator.