multiply that number by the number of minutes per batch. See the following formula:

The time only indicates the required continuous mixing time. It is not inclusive of the cleaning, the staging, or the transporting time of the material or the time required for you to lay the CMU. Batching procedures will vary with individual preference. Experience is the key to good results in obtaining the desired mix.

ESTIMATING LABOR

This section briefly covers labor estimates for concrete masonry units according to the Seabee Planner's and Estimator's Handbook, NAVFAC P-405. Table 4-4 shows the labor table from the P-405 on how to estimate labor. When using this table, you will see that 8" x 8" x 16" block takes "one person" (skilled labor) 160 man-hours to lay 1,000 square feet of CMUs. If you were to break this labor down into how many CMUs laid in an 8-hour period, it would be calculated as follows:

1000 sf of wall area= 1,125 CMU

160 man-hours ÷ 8 hour days = 20 duration days

1125 CMU ÷ 20 days= 56.25 CMU/day

Let's take the building example. How many man-hours (MH) will it take with a crew of three nonskilled and one skilled laborer? This is the ratio/proportion part of this calculation.

If 160 MH equals 1,000 SF of wall area (NAVFAC P-405), then, X (MH) equals the square footage of wall area

160 (MH) :1000 Sf :: x (MH) : 448 sf =

160 x 448 :: 1000 x

71680 ÷ 1000

x = 71.68 X = 72 MH

Another method you may use to calculate this is as follows:

In this equation, you simply cross multiply the following:

160 x 448 = 71680

X times 1000 = 1000 x, then divide

71680 ÷ 1000 x

X = 71.68 or 72 MH

In this example, it takes 72 man-hours to lay 448 SF or 504 CMUs. Now divide the number of MH by 8-hour days. It would equal 9 duration days. To see how close the estimate is - one person (skilled) lays

Table 4-4. - Labor Chart for Masonry