Masonry Magazine August 1978 Page. 18
COMPUTERIZED MASONRY COST ESTIMATING
By Clayford T. Grimm
Lecturer in Architectural Engineering
The University of Texas at Austin
KEY WORDS
Brick construction: Brick Masonry; Buildings, Costs, Cold Weather Construction; Columns, Concrete (Block); Construction, Contractors: Costs; Estimate; Labor; Management, Masonry; Productivity; Walls.
ABSTRACT
Mason productivity can be doubled and masonry construction costs greatly reduced by improved design and construction techniques, which have been well researched, thoroughly developed, fully proven and broadly reported. A computer program for estimating masonry wall and column costs has been written and verified by estimates conventionally prepared by experienced, successful, local mason contractors.
Introduction
Inability to predict construction costs accurately has plagued architects and contractors for more than two-thousand years. It is not unusual for masonry bids to vary 50% above the low bid. At about the time of Christ, the Roman historian Vitruvius wrote:
In the famous and important Greek city of Ephesus, there is said to be an ancient ancestral law, the terms of which are severe, but its justice is not inequitable. When an architect accepts the charge of a public work, he has to promise what the cost of it will be. His estimate is handed to the magistrate, and his property is pledged as security until the work is done. When it is finished, if the outlay agrees with his statement, he is complimented by decrees and marks of honour. If no more than a fourth has to be added to his estimate, it is furnished by the treasury and no penalty is inflicted. But when more than one-fourth has to be spent in addition on the work, the money required to finish it is taken from his property. Would to God that this were also a law of the Roman people, not merely for public, but also for private buildings.
Design decisions have a much more significant effect on construction labor productivity than do labor motivation, union work rules, or contractor efficiency, and this is particularly true of masonry construction.
Economic Effect of Design Decisions
Table 1 shows the effect of several design and construction changes on the unit wall cost to the owner of a "prototypical" cavity wall. Item 13 in Table 1 illustrates that design professionals concerned with mason productivity, beyond cocktail party lamentation, may reduce the cost of a typical masonry wall by 11% just by using larger units and modular design. The economy Norman size face brick (4 x 4 x 12 in. or 10 x 10 x 30 cm.) has the same proportion of face dimension as standard size brick and is indistinguishable from standard size brick at a short distance. Willingness of design professionals to accept modular design principles would alone increase mason productivity 11%. The resulting reduction in construction costs could bring some project in "under the money."
Item 3 in Table 1 illustrates that even the most elaborated masonry designs can be built at lower cost than that now being paid for many facades. Item 12 in Table 1 illustrates that mason contractors can greatly increase mason productivity and reduce construction cost by negotiating the use of corner poles into the work rules of their local labor contracts. Many such contracts now exist, but they are not typical. Efficient wall design and construction techniques reduce construction time lapse and alleviate labor shortages.
Bricklayer Productivity
The value of masonry construction in the United States in 1972 was $3.1 billion or about 3.3% of all building construction dollar volume. In that year 23,896 mason contractors had a total of 165,580 employees whose productivity has been investigated by more than 200 researchers in 18 nations, resulting in more than 250 reports on the subject.
Brick masonry costs are reduced by the use of large, straight, solid, unbroken, single wythe, wall areas faced one side and built of local, red, common, conventionally shaped, textured, packaged, large, brick units laid from adjustable scaffolding on low buildings with minimum supervision, during favorable weather, with the aid of corner poles, to modular dimensions, in common bond, with thin, flush cut mortar joints, the contents of which are high in air and lime, low in cement, and without admixtures. Some of those items which reduce cost also reduce quality.
TABLE 1
ECONOMIC EFFECT OF WALL DESIGN
AND CONSTRUCTION CHANGES
| No. | Design Change | Unit Cost, $ psf of wall | Relative Cost |
|---|---|---|---|
| 1. | None. "Prototypical cavity wall" | 6.73 | 1.00 |
| 2. | Use economy norman unglazed face brick (4 x 4 x 12) | 6.21 | 0.92 |
| 3. | Lay brick in Herring bone bond pattern | 11.08 | 1.65 |
| 4. | Use colored mortar in exterior wythe | 6.85 | 1.02 |
| 5. | Use modular design | 6.42 | 0.95 |
| 6. | Use close inspection | 7.17 | 1.07 |
| 7. | Use curved wall radius of 20 ft. | 7.35 | 1.09 |
| 8. | Use half as many wall openings with same area of openings | 6.51 | 0.97 |
| 9. | Build in Dec., Jan., and Feb. | 6.19 | 0.92 |
| 10. | Increase cost of brick 25% | 7.01 | 1.04 |
| 11. | Increase cost of all labor 25% | 7.61 | 1.13 |
| 12. | Use corner poles | 5.73 | 0.85 |
| 13. | Items 2 and 5 above combined | 5.97 | 0.89 |
| 14. | Items 2, 5, 8, 9, and 12 combined | 4.92 | 0.73 |
"Standard modular brick, 8x8x 16 in. lightweight concrete
masonry, insulated cavity wall built in a 10-story concrete-
framed building in Dallas, Texas, during the summer of 1977.
►In keeping with its policy to inform Mason Contractors in the field of the latest management and technological developments in the industry.
MASONRY presents this article by Clayford T. Griman. The statements, opinions and suggestions expressed by the author are not necessarily those of
MASONRY or its publisher, the Mason Contractors Association of Americo.-Ed.
22 MASONRY/AUGUST, 1978