shortages. For example, concrete ingredients, lumber, reinforcing materials, and everything else involved in mixing and placing the concrete, including equipment time, manpower, and man-hours, will be serious] y underestimated and ordered.
The need for accuracy in checking estimates is vital. Check quantity estimates to eliminate as many errors as possible. One of the best ways for you to check a quantity estimate is to have another person make an independent estimate and then to compare the two. Any differences should be noted to determine which is right. A less effective way of checking is for another person to take your quantity estimate and check all measurements, recordings, computations, extensions, and copy work, keeping in mind the most common error sources (listed in the next section).
Your failure to read all of the notes on a drawing or failure to examine reference drawings results in many omissions. For example, you may overlook a note that states "symmetrical about the center line" and thus compute only half the required quantity.
Errors in scaling obviously mean erroneous quantities. Great care should be taken in scaling drawings so that correct measurements are recorded. Common scaling errors include using the wrong scale, reading the wrong side of a scale, and failing to note that a detail being scaled is drawn to a scale different from that of the rest of the drawing. Remember that some drawings are not drawn to scale. Since these cannot be scaled for dimensions, you must obtain dimensions from other sources.
Sometimes wrongly interpreting a section of the specifications causes errors in the estimate. If there is any doubt concerning the meaning of any part of the specification, you should request an explanation of that particular part.
Omissions are usually the result of careless examination of the drawings. Thoroughness in examining drawings and specifications usually eliminates errors of omission. Use checklists to assure that all activities or materials have been included in the estimate. When drawings are revised after material takeoff, compare new issues with the copy used for takeoff and make the appropriate revisions in the estimate.
Construction materials are subject to waste and loss through handling, cutting to fit, theft, normal breakage, and storage loss. A person's 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 crew leader is responsible for making sure all required resources are identified. The crew leader must estimate materials, equipment, and labor required to complete each construction activity. All required resources are listed on CAS sheets. The scheduled start and finish dates for each activity are taken from the Level III bar chart and shown on the CAS sheet. The resources are then tied to the schedule, and any action required to track or request resources can be monitored on the CAS sheet.
The Naval Construction Regiments (NCRs) usually assign master activities to the projects. The master activities can be broken into at least five construction activities. Most commonly, master activities number between eight and ten. These activities identify functional parts of the facility and are often tied to a particular company or rating. It must be clear to all personnel involved in the planning process exactly what work is included in each master activity. That is the purpose of the master activity listing. By providing a good narrative description of each master activity, it will be clear to all where each work element falls. A good narrative description reduces the chance of omitting any work items from the estimate. Master activities for a typical building might look like the following list of items: