Concrete Demolition Unknowns (job site surprises that shouldn't surprise a demolition contractor)

Most concrete contractors, even though not demolition specialists, will have to demolish portions of structures as a part of their usual business. Knowing which method or combination of methods to use for demolition of reinforced or prestressed concrete structures is essential for a safe and profitable job.

Demolition work involves many of the hazards associated with construction. However, demolition incurs additional hazards due to unknown factors such as:

  • Deviations from the structure's design introduced during construction
  • Approved or unapproved modifications that alter the original design
  • Materials hidden within structural members
  • Unknown strengths or weaknesses of construction materials used on the project.

Many concrete contractors specialize in jobs that include demolition. Some contractors only do demolition- and leave the concrete construction to other concrete contractors.

Concrete Demolition Safety Considerations

All personnel involved in a demolition project must be fully aware of the various hazards, which may be encountered, and the safety precautions that may be taken in order to control the hazards. Beginning any type of demolition project without all the players knowing every aspect of the plan is an invitation for something to go wrong.

Hold daily pre-job safety meetings with all workers, stressing safety basics, common sense, alertness, and proper use of demolition equipment. The meetings should cover inspection, proper use and maintenance of all tools and equipment.

Also, keep in mind that OSHA mandates an engineering survey be undertaken by a competent person prior to beginning a demolition project. This is necessary to determine the condition of overall structure, and also the possibility of the unplanned collapse of any portion of the structure. Safe floor loads should be determined to prevent overloading with demolition.

Hand Tool Hazards

The vast majority of hand tool injuries occur when the proper tool is not used for the job. Workers are often tempted to use whatever is at hand to hammer, pry or chip instead of going to get the proper tool. When the wrong tool is used for the job, injury is much more likely to occur than if the right tool is used correctly.

Wrecking bars or crowbars:
Make sure they have a sharp point or keen edge that allows the bar to get a firm hold on the object being moved. Using poor substitutes for these tools, such as pieces of pipe, angle, iron or other building materials can be a serious mistake, since the are more likely to slip or break and cause injury.

Wire and bolt cutters:
These require the wearing of eye protection at all times. Dont use a cutter too small for the task, or try to gain added leverage by putting a length of pipe over its handle. These tools are made to withstand a certain amount of stress, depending on their size. Dangerously over-stressing them can result in injury.

Sledges and hammers:
These also require workers to wear eye protection in order to prevent possible blindness from concrete chips and splinters. Inspect equipment prior to use for unacceptable conditions such as mushroomed heads, cracks, looseness and splinters.

Shovels:
Shovels are often thought of as a relatively safe construction tool, but improper use can cause serious back injuries, as well as injuries to other parts of the body. Proper use requires a firm, solid stance, and moving the entire body in the direction the material is being thrown instead of twisting the back or knees.

Power tool hazards

Machine-Mounted Tool Hazards

Falling debris is of particular concern in demolition projects, both in terms of the workers actually doing the demolition work, and other workers or bystanders. Make sure the demolition area is clear of all unnecessary personnel prior to work. Large attachments, such as those on excavators, require a viewing area of at least 75 feet, and one of about 30 feet for smaller attachments, such as those mounted on skid-steer loaders, backhoe loaders and mini-excavators. Make sure all attachments are installed according to the manufacturer's guidelines. Refrain from modifying tools or equipment without first contacting the manufacturer.

When an excavator, skid-steer loader, or other piece of equipment is used on a floor deck, floor openings must have protective curbs installed to prevent the equipment from falling through the opening.

Excavators should have cab safety screens installed over top and front glass when demolishing any type of overhead structure, as well as a falling objects protection structure (FOPS). Cab windows should be of transparent, shatterproof glass.

The ball on a ball and crane should not exceed the smaller of 50% of the crane's rated load capacity, or 25% of the breaking strength of the wire rope on which the ball is suspended. Check with the crane manufacturer before beginning work to determine if the crane can be used safely for demolition, as a demolition ball places unusual stresses on a crane boom.

Clothing and Dress Tips

A large part of demolition safety involves proper dress and the use of appropriate safety accessories, especially when using power tools.

  • Do not wear loose clothing that can get caught in machinery
  • Pull long hair back
  • Remove any jewelry that can interfere with safe machinery operation
  • Wear safety goggles or glasses with side protection
  • Use a face mask in dusty applications, ear plugs when the site is especially noisy or for extended periods of work
  • Heavy work gloves should be worn to protect against the steady vibration of power tools and the heat that can be generated, especially in the bit
  • Wear steel-toed shoes or boots