Estimation, Types of Estimates
Estimation, Types of Estimates
For all engineering works it is required to know beforehand the probable cost of construction known as estimated cost. If the estimated cost is greater than the money available then attempts are made to reduce the cost by reducing the work or by changing the specifications. In preparing the estimate, the quantities of different items are calculated by simple maturation method and from these quantities the cost is calculated. (Knowledge of drawing is necessary for this). In preparing the estimate one has to go into detail of each item big or small, nothing can be left or missed. Accuracy in estimate is very important, if an estimate is exceeded it becomes a very difficult problem for engineers to explain, to account for and arrange for the additional money. Inaccuracy in preparing estimate, omission of items, changes in designs, improper rates, etc. are the reasons for exceeding the estimate, though exceed in the rates is the main reason. The rates in the estimate provided for the whole work, which consist of the cost of the materials, cost of transport, cost of labor, cost of scaffolding, cost of tools and plants, cost of water, taxes, establishment and supervision cost, reasonable profit of contractor, etc.
An estimate is a computation or calculation of the quantities required and expenditure likely to be incurred in the construction of a work. The estimate is the probable cost of the work and is determined theoretically by mathematical calculations based on the plans, drawings and the current rates.
The primary object of estimate is to enable one to know beforehand, the cost of the work.
Types of Estimates
Generally there are two different types of cost estimates
Rough Order of Magnitude (ROM) Estimates:-
These types of estimates are the first step in project preparation. They provide with a cost range, so one can get an idea of the size and scope of the project. ROM estimates are usually comparative and are based on the estimator’s experience as well as historical data on similar projects. A department may use this kind of estimate for funding requests and budget planning, and will need to get detailed cost estimates before construction or renovations begin. This is usually used for administrative approval.
Detailed Cost Estimates:-
A detailed cost estimate is made once funding has been approved or identified for a project. The detailed estimate will give the specific breakdown of project costs, and one will need to have a preliminary design to get this type of estimate. Then fully investigate existing building conditions and evaluate all remodeling projects for heating and air conditioning capacity, electrical service, plumbing, potential hazardous materials, and interior elements such as paint and carpet. It will also provide estimates of completion dates and work on coordinating critical deadlines at the same time. This is used for technical approval.
After detailed estimation there will come an expected cost for the project that is called estimated cost.
The actual cost of a work is known at the completion of the work. Accounts of all expenditure are maintained day to day during the execution of work in the account section and at the end of the completion of the work when the account is completed, the actual cost is known. The actual cost should not differ much from the estimated cost worked out at the beginning.n, Types of Estimates
In order to prepare an estimate of any residential or commercial construction project, you will first need to have the construction takeoff that contains the list of all materials required for the project and their quantities. There are companies that provide quantity take-off services using latest softwares like Plan swift and blue beam. Once you get the quantity takeoff, you just need to put the unit rates of each line item in order to get the preliminary cost estimate of your construction project. Estimation