Estimating in Building Construction

Masonry 121

determine what sizes and shapes are available (Figure 11.5).

If the order requires a large number of special units, it is

very possible that the local manufacturer will produce the

units needed for the project.

Concrete blocks are available either as heavyweight or

lightweight units. The heavyweight unit is manufactured out

of dense or normal weight aggregates such as sand, gravel

and crushed limestone, cement, and water. Lightweight units

use aggregates such as vermiculite, expanded slag, or pumice

with the cement and water. The lightweight unit may weigh

30 percent less than the heavyweight unit, although it usually

costs a few cents more per unit and usually has a slightly

lower compressive strength.

The specifications will have to be checked to determine

the size, shape, and color of units, as well as the conformance

with some set of standards such as that of the American Society

for Testing and Materials (ASTM), which sets up strength

and absorption requirements. If a specific fire rating is desig-

nated for the units, it may require the manufacture of units

with thicker face shells than are generally provided by a par-

ticular supplier. Check also for the type of bond, mortar, and

any other special demands. If the estimator is unfamiliar with

what is specified, then he or she can call the local suppliers to

discuss the requirements of the specifications with them to be

certain that what is specified can be supplied. Some items

such as units cured with high-pressure steam curing are

unavailable in many areas, and in such a case the estimator

(and often the suppliers) may want to call the architect/

engineer to discuss with them the problem of supplying

the item.

FIGURE 11.3.Brick Patterns.

FIGURE 11.4.Shapes of Mortar Joints.