Noting the time required for roughing-in the lead work and setting the fixtures in the bath room will show the estimator how the labor he estimates for any building can be checked.

The roughing-in for the three fixtures cited took one day, and another day was required for setting the fixtures. That makes two days for three fixtures, or two-thirds of a day for each fixture. By allowing, now, one more day to a bath room, or one-third of a day for each fixture for the time required installing the house drain, running the stacks, branches, water pipes, pump pipes and doing other work of a similar nature, it makes an average of one day's labor for each fixture in the building. Counting the number of fixtures, therefore, and comparing the number with the days allowed for one workman to do the work will show whether any serious error has been made in his calculation of time. If he has allowed either more or less days than there are fixtures, and the difference is great, he is put upon inquiry to go over his figures again to learn the cause of the discrepancy or find the error, if there be one.

It must be borne in mind that the foregoing explanation is given merely to illustrate, and cannot be depended upon as a check in all cases. In flat buildings, hotels, office buildings and other structures where the fixtures are pretty well bunched, the day-per-fixture rule will serve very well for a check. In buildings, however, where the fixtures are scattered and most of the labor is in the roughing-in, or where heavy, elaborate and unusual fixtures are installed, the same method can be employed, but a different allowance must be made to suit the case.

Each estimator should compile for himself a schedule of time required for different classes of buildings where he has installed the work, and from this data obtain coefficients that will show in his individual shop what time to allow per fixture, as a check on different classes of work.

When estimating the labor for a building, the materials of which the structure is built and the quality of the material must be carefully looked into. This is of more importance in old buildings than in new, although it is a point well worth considering in any case. Many of the old Government buildings which were erected to endure for centuries have walls, floors, partitions and roofs of such hardness that a day will often be required to cut through the mason work, where in ordinary structures a half hour would accomplish the desired result. A reinforced concrete building, likewise, is much harder to install a plumbing system in than a frame house, for the cutting for pipes, hangers and other purposes requires a much greater expenditure of labor.

Again, it might be well to emphasize the fact that the estimator who depends on the average day's work of the craft will lose most of the work he estimates on. Averages are good as a check and as a basis for arriving at the real capacity of workmen, but averages are not to be depended upon in estimating. The rule is, know your men, know your buildings and understand fully the work to be performed,then from the fulness of this knowledge figure out the number of days required to do the work by one of the average workmen in the shop. Having determined this quantity, check it with the fixture-per-day rule, applicable to the building, and there will be little danger of going astray on the cost of labor.