Construction Site Hazards – Causes and Classification of Accidents in Buildings Under Construction

Safety in Building Construction

Quite often accidents occur during construction of buildings. There can be various reasons for these accidents. These can be carelessness on the part of workers, improper planning and wrong sequence of operations, poor quality of the materials, bad workmanship, and inadequate training with respect to handling of the machinery and equipment. The accidents can be minor or major causing loss of life or impairment to the human body. In turn, there can be financial losses and delay in the completion of the project.

As such, it is essential to ensure the safety of workers engaged in the construction of buildings and to protect them from the injuries arising out of accidents. In olden times, buildings were normally of smaller size and height. But nowadays large numbers of multi-story buildings are being constructed for both residential and office purposes. The chances for accidents are more in the case of construction of high rise buildings. The available statistics reveal that about 11% of all the occupational injuries are from the construction industry.

Buildings under Construction

Causes of Accidents

There are many causes for accidents. These are carelessness of workers in handling of the equipment, technical defects in the equipment, defects in the system planning, bad quality scaffolding and formwork, etc. These defects can be broadly classified into:

1. Execution of work

  • Use of defective materials
  • Construction defects
  • Wrong processing of materials

2. Role of workers

  • Carelessness
  • Unauthorized acts
  • Unskilled working

3. Equipment

  • Defects in the equipment
  • Insufficient maintenance
  • Improper handling

4. Planning

  • Award of work to incompetent agencies
  • Lack of proper supervision
  • Absence of coordination

Classification of Accidents

Accidents can be grouped under the following headings:

1. According to the severity of the injury

  • Major accident
  • Minor accident
  • Accidental hazard

2. According to the nature of the injury

  • Death
  • Temporary disablement
  • Permanent disablement
  • Partial disablement

3. According to the cause of accident

  • Equipment fault
  • Construction site falls
  • Trench collapse
  • Crane failure

Role of Various Agencies in Safety Management

For ensuring safety in construction, everybody involved has to play their role effectively. However, the primary responsibility is that of management. They have to coordinate the work of different groups. The concerned groups are:

  1. Employer -The employer should hold the equipment, premises, and the passages in such a manner that the workers can work without any hazard, and sufficient precautions have to be taken to avoid any accident. The employer should ensure that the work is supervised properly and that safety regulations are scrupulously followed. Particular attention should be taken to ensure that persons having physical or mental disorders are not employed.
  2. Workers – Workers should take all possible steps to protect their individual safety as well as that of their coworkers. They should wear proper dress, helmets, hand gloves, etc. as required and prudent. They should be conversant with the safety regulations, especially when operating machineries.
  3. Designers – The designer should take into consideration the relevant codes of the region when designing the structures. The quality of the materials used for fabrication should be clearly spelled out and the specifications should be written without any ambiguity.
  4. Manufacturer – The manufacturer of the equipment and machineries should ensure that the materials used are of good quality and due care was taken in every stage of manufacture and assembling.

Safety in Various Stages of Construction

  • Excavation – Excavation shall be done with proper care to the safety of workers, avoiding disturbance to adjoining property and underground electric cables, water supply lines, sewage pipes, etc. The excavated materials and other items should be removed from the work site as early as possible so that it should not act as a hindrance to the ongoing work and workers can move freely. Proper signals and warning boards should be erected so that people will be aware of the work and will take necessary precautions.
  • Piling for foundations – Piling is adopted for deep foundations of high rise buildings. There are bored piles and driven piles. Sufficient precautions should be taken so that no damage is caused to the adjoining structures.
  • Walls – Scaffolding used for wall construction should be checked to see their strength and stability. Platforms must be rigid and non-slippery. The ladders should also be fabricated from strong and sturdy materials, and the joinery and bracing should be properly done and secured.
  • Formwork of roofing – The formwork should be designed and fabricated properly so that they do not collapse during the course of construction. All vertical members shall be properly joined and braced.


Safety Benefits

Accidents cause financial hardships to the worker as well as to the contractor. The worker will have to meet the expenses towards the treatment while the contractor will have to replace the defective equipment and machinery. The accidents may retard the progress of work which will lead to price escalation.

In addition to the financial losses, the injured worker will have to undergo both physical and mental hardships. This is certain to keep the morale of the workers down, and also in the eyes of the general public, the image of the company will be at a lower ebb.

Safety Measurement

Injury severity Rate (ISR)

This is defined as the number of days lost due to injuries for 100 man hours worked.

ISR = Number of days lost x 1000 number of man hours worked

Injury Frequency Rate (IFR)

This is defined as the number of disabling injuries per one-hundred thousand man hours worked.

IFR = Number of disabling injuries x 100000 total number of man hours worked

Injury Index

Injury Index= (ISR x IFR )/ 1000


Safety is of paramount importance in the construction of buildings. Lack of safety measures will lead to accidents which in turn will culminate in the loss of life, injury, financial losses, delay in the completion of the project, etc.


  • Architectural Hand Book by Institution of Engineers, Calicut, 1999