Figure 2-14. - Production efficiency graph.
The activity duration is increased by including the availability factor to account for time lost from the project site. The actual crew you would expect to see on the jobsite on the average day would be the assigned crew multiplied by the availability factor. Always use the availability factor.
If in the drywall example, you had a crew of 12 assigned, 1 hour for lunch each day, total travel to and from jobsite is 1 hour, and a total of 30 minutes for breaks each day, how long would it take to complete this task ( if the availability factor 0.75, and the man-day equivalent is .9375)? Remember to use the revised man - day estimate, which includes the delay factor. The equation would be written as follows:
Duration = 70 ÷ 12 ÷ 0.75 ÷ .9375 = 8.3 or 9 workdays.
Once the master activities have been broken into construction activities, you will need to use a CAS sheet (figs. 2-15 and 2-16) for each activity. In addition to the activity description and the scheduled dates, all the required resources are shown on the front. Safety and QC requirements are on the back. The space at the bottom of the back page should be used for man-day and duration calculations.
The CAS sheets should be able to stand alone. The CAS sheets should contain all of your notes, information, and calculations pertaining to man-days, durations, tools, and equipment. In this way, if you are not available, someone else can use this information and the project can continue. It is very important that CAS sheets be filled out correctly. Almost all of your remaining planning is driven from the CAS sheets. Always use a pencil to fill them out, because they change constantly.
MATERIAL ESTIMATES are also used to procure construction material for a given project, to determine whether sufficient material is available to construct a given project, and to determine the labor involved to install the material. The following is a suggested procedure for preparation of a material estimate. First, obtain a work element checklist by referring to the P-405, then estimate the quantity of material needed for each activity by using the P-405 and any previous experience. Use the conversion chart from table 2-5, whenever possible, for estimating waste factors and the conversion of material. This conversion should be done on a work sheet when the estimator records how each quantity of material was obtained. A typical material estimate work sheet is shown in figure 2-17. Each step can readily be understood when the work sheets are reviewed.Continue Reading