Productivity Data

The four topics in this category are materials, labour, equipment, and risk. The development of reliable data for these factors is to a large extent determined by the exercise of judgement on the part of the estimator. Like factual data, productivity factors are not permanently fixed, although they can also be established within 

acceptable margins with respect to points or period of time. 

Materials 

Most construction materials are marketed in standard sizes, containers, or unit quantities such as sheets or boards, cans or drums, or in loose form such as sand or gravel. When considering some prefabricated materials, such as plywood or concretion block?, the estimator has to decide how much work can be done with whole units and how much with units (resulting in some waste if whole units have to be cut). When considering products such as paint or asphalt the rate of coverage is going to vary depending upon the type of material supplied, the type of surface treated, the type of equipment used, the skill of the applicator and general environmental conditions at the place of the work. Each product has its own characteristic factors of coverage and waste, and it is possible for the estimator to acquire or prepare tables or charts to indicate such characteristics for common materials likely to be encountered in the work of any trade. 

Labour 

Labour productivity, probably, is the most difficult factor of the four to predict with any accuracy. In general, there are two primary reasons for the difficulty: first, the large number of variables that have to be taken into account, and second, the somewhat arbitrary decisions that have to be made by the estimator about many of these variables. Some important aspects of labour productivity are discussed in subsequent paragraphs. 

General  Factors 

• Proper management and direction of work force. 
• Time of the year and weather conditions. 
• Availability of qualified tradesmen. 
• Quality and quantity of organisation and Congestion at the place of work. 
• Location of project - labour productivity is generally higher in town than in rural areas. 
• Institutional work is generally less productive than commercial work. 
• General level of business activity in the region. 
• Worker morale, pay rates, absenteeism. 
• The training and education of supervisors. 
• Building codes. 
• Union regulations. 

Specific Factors 

• Nature of work of each trade. 
• Amount of work to be done. 
• Whether the work has to be done on a continuous or intermittent basis. 
• The time available to do the work. 
• The complexity or interest of each work task or item. 
• Logistics of organisation to keep workers fully and productively occupied. 

Distribution of Time 

Within the work of any specific trade,  there are proportions of time which are clearly more productive than others. For example, 

• Fully productive time - i.e. the work of the trade or related work is actually being performed by workers 
• Semi productive time - i.e. planning or other arrangements lo do some actual work are considered or discussed 
• Non-productive time - i.e. Activities such as rest breaks, delays and other diversions 

This would mean that productivity levels are always less than 100% (time-wise). In particular, carpenters are found to achieve just over 50% productivity - but masons can achieve just under 75% productivity under typical and normal conditions of work. Several points arise out of these features of productivity which are of importance to the estimator. They are 

• Each trade has its own characteristic feature. 
• The proportion of productive to non-productive time is a reflection of the nature of work and its organisation. 
• The estimation of probable time to do work of every type must include an allowance  for the appropriate proportion of semi-productive and non-productive time. 
• Improvement of productive time is largely a function of management, not of labour.