the copy used for takeoff and appropriate revisions made in the estimate.
Construction materials are subject to waste and loss through handling, cutting to tit, theft, normal breakage, and storage loss. Failure to make proper allowance for waste and loss results in erroneous estimates.
Other error sources are inadvertent figure transpositions, copying errors, and math errors.
The activity estimate provides a basis preparing the estimates of material, equipment, manpower requirements. An activity estimate, for and for example, might call for rough-in piping in a floor slab. In an activity estimate, your immediate concern is to identify the material necessary to do the task - pipe, fittings, joining materials, and so forth. The equipment estimate for this activity should consider vehicles for movement of material and special tools, such as portable power tools, a threader, and a power vise. From the scope of the activity and the time restraints, you can estimate the manpower required. The information shown in the activity estimate is also useful in scheduling progress and in providing the basis for scheduling deliveries of material, equipment, and manpower to the jobsite.
The techniques discussed in the next paragraphs will help you produce satisfactory activity estimates. But, before doing anything, you should become knowledgeable about the project by studying the drawings. Read the specifications and examine all available information concerning the site and local conditions. Only after becoming familiar with the project are you ready to identify individual activities. Now, here are two ideas that will help you make good estimates.
First, define activities. They may vary depending on the scope of the project. An activity is a clearly definable quantity of work. For estimating and scheduling, an activity for a single building or job should be a specific task or work element done by a single trade. For scheduling of large-scale projects, however, a complete building may be defined as an activity. But, for estimating it should remain at the single-task, single-trade level.
Second, after becoming familiar with the project and defining its scope, proceed with identifying the individual activities required to construct the project. To identify activities, be sure each activity description shows a specific quantity of work with clear, definite limitations or cutoff points that can be readily understood by everyone concerned with the project. Prepare a list of these activities in a logical sequence to check for completeness.
Material estimates are used to procure construction material and to determine whether sufficient material is available to construct or complete a project. The sample forms shown in figures 9-2, 9-3, and 9-4 may be used in preparing material estimates. The forms show one method of recording the various steps taken in preparing a material estimate. Each step can readily be understood when the work sheets are reviewed. A work sheet must have the following headings: Project Title, Project Location, Drawing Number, Sheet Number, Project Section, Prepared By, Checked By, and Date Prepared.
ESTIMATING WORK SHEET. - The Esti- mating Work Sheet (figure 9-2), when completed, shows the various individual activities for a project with a listing of the required material. Material scheduled for several activities or uses is normally shown in the "Remarks" section. The work sheet should also contain an activity description, the item number, a material description, the cost, the unit of issue, the waste factors, the total quantities, and the remarks. The Estimating Work Sheets should be kept by the field supervisor during construction to ensure the use of the material as planned.
MATERIAL TAKEOFF SHEET. - The Material Takeoff Sheet (MTO) is shown in figure 9-3. In addition to containing some of the information on the Estimating Work Sheet, the MTO also contains the suggested vendors or sources, supply status, and the required delivery date.
BILL OF MATERIAL. - The Bill of Material (BM) sheet (figure 9-4) is similar in content to the Material Takeoff Sheet. Here, though, the infor- mation is presented in a format suitable for data processing. Use this form for requests of supply status, issue, or location of material, and for preparing purchase documents. When funding data is added, use these sheets for drawing against existing supply stocks.
Between procurement and final installation, construction material is subject to loss and waste.Continue Reading