A COMBINATION COST AND PROGRESS CHART

In "Engineering-Contracting" for Dec. 17, 1913, is an article by Mr. E. W. Robinson entitled "An Office System for Construction Work Covering Records of Plans, Progress and Cost and Bookkeeping Methods, which is a very clear and suggestive exposition of this subject. A system

FIG. 163. Chart giving summary of labor and material expenditure and plant cost on construction job.

of chart-making which illustrates itemized expenditures to date, the unit costs of the same, the amount and percentage completed of each class of construction and for the job as a whole, will alone be considered in this section.

For a typical concrete construction job, three progress charts are made

out; one to cover labor costs only, one showing expenditure for materials and other accounts, and a third giving a summary of the other two: only the first and third are reproduced here, the second being shown in Fig. 92 (Chap. VI).

COMPLETED

93.73% 1,875,629 Cu. Yds.

Completed

As shown in these figures, the charts "consist of parallel vertical columns which are filled with the particular kind of cross-hatching for the month in which the work was done. About two-thirds the way up from the bottom a heavy horizontal line is drawn through the columns to represent the estimated quantities and costs, or 100 percent. This line also represents the time for completion as shown in the contract. Then, if there is estimated to be 1,000 cu. yd. of concrete to be poured, and the total time for completing the job is 4 months, if at the end of the second month there are only 250 cu. yd. in place, the cross-hatching in the quantity column under the heading of "concrete" will be advanced from where it was the previous month to a point 25 percent from the bottom line of the chart, while in the time column the same style of cross-hatching will be advanced to a point 50 percent from the bottom. This will show, for that particular item, that we are only 25 percent completed, when to finish according to schedule time we should be 50 percent completed. On a large job with many items of nearly equal importance, it requires judgment to state the stage of the work from these charts, for the reason that when our time is 50 percent gone several items may be 99 percent completed and others only 5 percent and the relative importance of the different items must be taken into account. The principal value of the charts, however, is in showing the unit costs from month to month, and their variation according to quantities, locations, weather, etc. The same variation in regard to cost may exist as in regard to time. That is, several items may run 200 percent or even more above the estimated cost for that item, and yet the job as a whole be completed below the estimate. If the unit costs as a whole are running close to the estimated costs, then the total actual cost column, when compared with the time column, shows a fairly accurate representation of the rate of progress.

Uncompleted 124,371 Cu, Yds.

Uncompleted

FIG. 164.-"Clock chart" method of illustrating percentage of work completed (on Gatun locks).

"The unit costs for each month are written in small figures in the total cost column.

"The third chart (Fig. 163) is merely a summary of the first two, together with the plant expense chargeable to that job. The first cost, in the case of new equipment, and the invoiced value in the case of second-hand equipment, is charged directly to each job, as it is placed on the work. Then the sale price, if sold, or the invoiced value if moved to another job, is given as a credit, leaving the balance as the depreciation or cost of plant for that job."

THE "CLOCK CHART" METHOD OF ILLUSTRATING PERCENTAGES

This method is particularly adapted to illustrate reports, etc., intended for non-technical readers, and to show succinctly the relation of complex figures to one another in technical articles.

Fig. 164 is taken from one of the charts issued by the Isthmian Canal Commission to illustrate the progress of the work on the Gatun Locks. A diagram of the lock shows the uncompleted parts in hatched lines, and the clock chart shows at a glance the percentage completed.

FIG. 165.-"Clock chart" method of illustrating the relative compensation and classification, etc., of the employees of the city of Chicago.

Fig. 165 is taken from a report of the Civil Service Commission of Chicago on the compensation and classification of the employees of the City of Chicago. (Eng. News, May 2, 1912.)

The charts are suitable for placing before a board of non-technical men, and, with appropriate explanations, would serve to carry home to them points which mere tables of figures and percentages would never do.

1891