Masonry Magazine January 1970 Page. 35
NCMA TEK 16
An Information series from National Concrete Masonry Association
Cold-Weather Concrete Masonry Construction
General
Suspension of concrete masonry construction during cold weather results from concern over technological feasibility and assumed additional costs. As a consequence high rates of unemployment occur during the winter months, and are accompanied by large material inventories and idle production facilities. Full annual use of the existing capacity in the construction industry would not only produce additional business of significant advantage to architects, engineers, and builders, but would also reduce the seasonal unemployment in the building trades. Owners would also profit by additional revenue resulting from earlier completion of construction and occupancy of structure.
The economics of cold-weather construction have not always been adequately analyzed, with the result that construction projects have been interrupted or delayed because it was assumed that cold-weather construction was unprofitable. Recent examinations of completed projects have proven this not to be the case. Of particular interest is the experience noted on many cold-weather projects in foreign countries where cold-weather construction is common. The Canadian Construction Association performed a survey of winterizing costs on 106 projects of total value at nearly fifty million dollars. The costs ranged between % of 1% and 12% of total contract price, but these were offset more than twice by extra revenue from earlier availability.
The economic advantages to contractors resulting from winter building include:
1. Savings in overhead costs. This includes the cost of management, administration, depreciating plant and equipment, insurance, and miscellaneous expenses, all of which continue when construction is stopped.
2. Savings in interest on capital invested. Money invested in materials purchased for work delayed or interrupted by cold weather could otherwise be invested in a bank and the interest is lost. Interest charges on construction loans to the contractor fall in the same category.
3. Savings by reducing the losses from interruption and resumption of work. These losses result from time being spent by workers finding tools and re-adapting to the working routine. Savings also accrue from reduced delays, due to ready availability of labor, building materials, and equipment in the winter season.
4. The possibility of making greater profits. Construction during periods of cold season inactivity may mean significant extra profit for the contractor, while absolutely no profit can accrue when construction is stopped due to cold weather.
5. Savings from retention of the work force. Contractors who build throughout cold weather are able to keep work crews employed year-round, and avoid the costs of recruiting and indoctrinating new work forces in the spring. The need to pay costly premium wages for overtime work during the summer peak period is also reduced.
6. Savings from avoiding inflation. Building cost indices have risen consistently each year. The index in January is usually about 3% lower than in the following summer. This consideration in itself indicates that it may be more economical to proceed with cold-weather construction rather than postpone the work until summer.
Planning
While increases in construction costs for cold-weather operations can more than be offset by increased savings and profits, successful results are not likely to occur without detailed advance planning. Builders who have been building in the same area for a number of years can plan their winter operations on the basis of their own weather experience, but should also evaluate the information available from the Environmental Science Service Administration (Weather Bureau). This information includes forecast data disseminated by news media, and information published in the form of bulletins and maps relating to observations and predictions. Factors which are of importance to cold weather masonry construction include such items as temperature, wind, rain, and snow. Combination of factors can affect construction workers much more seriously than any single factor. For example, wind and temperature together have a greater impact than temperature alone. Examination of the following chart (Table 1) illustrates that the cooling effect of a 20 mile per hour wind at
Table 1. Wind Chill Effect
When thermometer reads (F)
When the wind blows at the m.p.h. below, it reduces effective temperature to
5
10
15
20 25
30
+40
37
28
22
18
16
13
+30
27
16
9
4
0
-2
+20
16
4
-5
-10
-15
-18
+10
6
-9
-18 -25 -29
-33
0
-5
-21
-36 -39
-44
-48
-10
-15 -33
-45
-53 -59 -63
-20
-26 -46
-58
-67
-74
-79
-30
-36 -58
-72
-82
-88
-94
-40
-47
-70
-88
-96-104
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