The activity estimate provides a basis for preparing the estimates of material, equipment, and manpower requirements. An activity estimate, 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 Estimating 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 information 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.
Figure 9-2.-Typical Estimating Work Sheet
Figure 9-3.-Typical Material Takeoff (MTO) Sheet.
Figure 9-4.-Sample Bill of Material (BM) sheet.
This loss may occur during shipping, handling, storage, or from the weather. Waste is inevitable where material is subject to cutting or final fitting before installation. Frequently, material, such as lumber, conduit, or pipe, has a standard issue length longer than required. More often than not, however, the excess is too short for use and ends up as waste. Waste and loss factors vary depending on the individual item and should be checked against the conversion and waste factors found in NAVFAC P-405, appendix C.
CHECKLISTS.- Use checklists to eliminate any omissions from the material estimates. Prepare a list for each individual project when you examine the drawings, specifications, and activity estimates. This is the practical way to prepare a listing for the variety of material used in a project. The listing applies only to the project for which it has been prepared. If no mistakes or omissions have been made in either the checklist or estimate, the material estimate will contain a quantity for each item on the list.
LONG LEAD TIMES.- Long lead items are not readily available through the normal supply system. They require your special attention to ensure timely delivery. Items requiring a long lead time are nonshelf items, such as steam boilers, special door and window frames, items larger than the standard issue, and electrical transformers for power distribution systems. Identify and order these items early. Make periodic status checks of the orders to avoid delays in completing the project.
PREPARING MATERIAL ESTIMATES.There are several steps for preparing a material estimate. First, determine the activity by using the activity description with the detailed information furnished by the drawings and plans to provide a quantity of work. Convert this quantity to the material required. Next, enter the conversion on a work sheet to show how each quantity was computed, as shown in figure 9-2. Include sufficient detail; work sheets need to be self-explanatory. Anyone examining them should be able to determine how the quantities were computed without having to consult the estimator. Allowances for waste and loss are added after determining the total requirement. All computations should appear on the estimate work sheet, as must all notes relative to the reuse of the material. Material quantities for similar items of a project are entered on the Material Takeoff Sheet or Bill of Material. Figures 9-3 and 9-4 become the material estimate for the project.
Equipment estimates are used with production schedules to determine the construction equipment requirements and constraints for Seabee deployment. Of these constraints, the movement of material over roadways is frequently miscalculated. In the past, estimators used the posted speed limit as an average rate for moving material. This was wrong. Equipment speed usually averages between 40 to 56 percent of the posted speed limit. Factors, such as the road conditions, the number of intersections, the amount of traffic, and the hauling distances, vary the percentage of the posted speed limit. You should consider the types of material hauled; damp sand or loam, for example, is much easier to handle than clay. Safety (machine limitations), operator experience, condition of the equipment, work hours, and the local climate are other factors.
Equipment production must be determined so that the amount and type of equipment can be selected. Equipment production rates are available in the
Figure 9-5.-Sample equipment estimate (sheet 1 of 2).
Seabee Planner's and Estimator's Handbook. The tables in this handbook provide information about the type of equipment required. Estimate the production rate per day for each piece of equipment, You should consider the factors discussed above, along with information obtained from NAVFAC P-405 and your experience. The quantity of work divided by the production rate per day produces the number of days required to perform the project. After determining the number of days of required equipment operation, consult the project schedule to find the time allotted to complete the activities. Prepare the schedule for the total deployment. Use the project schedule to determine when the work will be performed. The schedule should also indicate peak usage. It may have to be revised for more even distribution of equipment loading, thereby reducing the amount of equipment required during the deployment.