Schedule Compression and Time-Cost Trade-Off - Construction Project Scheduling and Control - page 241

Disabilities Act (ADA) or a new building code. Along with the increase in
demand, there is usually a price increase. This increase may slowly go back to
normal after the demand tapers off and/or the supply increases to match the
demand. Avoiding demand spikes, if the owner has such a luxury, results in
lower prices and, in some instances, better quality.
2. Productivity fluctuation : Labor productivity is subject to a host of factors.
Weather is one of the most influencing factors, particularly for outdoor
activities. During extreme weather conditions, workers' productivity is usually
impaired. In addition, they may work reduced hours. 12 Working overtime
(extra hours per day or extra days per week) may result in a reduction in
productivity (as discussed earlier). There are several studies on the effects of
overtime, but they do not necessarily agree on the conclusion. However, the
author recommends against using overtime for extended periods of time.
Since the construction industry is not fully automated, equipment's pro-
ductivity is directly linked to labor's productivity.
3. Weather and climate : In addition to its effect on productivity, weather may
also affect the behavior of certain materials. Concrete, for example, takes more
time to cure in cold weather and may require heating and/or insulating form-
work. In extremely hot weather, concrete has a different problem. It hardens
quickly, unless retarding agents are added to the mix, and then needs special
curing. Extreme weather affects other materials, too, such as asphalt and adhe-
sives. Other materials may become brittle in extremely cold weather, which
makes them less workable and more subject to breakage. Excessive rain ham-
pers outdoor activities. Rain may also come with lightning, which poses a
danger during outdoor activities, particularly to those workers using cranes and
tall equipment. Moisture may slow down the curing of concrete or the behav-
ior of adhesives, and it also may adversely affect stored materials such as wood.
You may want to avoid outdoor construction in areas where seasonal monsoon
rains, hurricanes, tornados, floods, and other forms of extreme weather occur
during such seasons. While scientists may use various methods, such as simu-
lation, to forecast the timing and severity of such disasters, they cannot make
accurate predictions.
Weather also may affect logistics and materials storage. Extreme weather
poses difficulties and sometimes hazardous conditions on roads. Stored
materials under extreme weather conditions have to be protected with special
methods that may be expensive. The time of year may have an impact on work
hours, which differ between summer and winter. Depending on the latitude,
there may be fewer daylight hours in the winter than in the summer. This may
require the contractor to use artificial lighting.
4. Locale : This factor encompasses other factors that are not included above, such
as local culture and government regulations.
12 In some countries in the Arabian/Persian Gulf, government regulations forbid outdoor work during certain
daytime hours in the summer. In extremely cold regions, local law may prohibit outdoor work if the
temperature dips below a certain limit.