Types of Demolition
Navigating through the complex world of demolition? Here is some information that will help you to understand how the different types of demolition work.
Selective demolition is defined as a careful demolition procedure whereby parts of a structure are removed while the primary structure is protected and remains intact. Selective demolition procedures use a combination of hand labor and small, specialized equipment. Examples of selective demolition are listed below:
- Removal of interior features such as walls, ceilings and utilities-this is a very common procedure during remodeling work.
- Cutting openings in walls and floors for new utility services, stairwells, elevators, windows, doors etc.
- Removing entire floors for major remodeling projects.
- Removing portions of structures that have become deteriorated or otherwise unusable.
- Removing portions of structures that have been damaged by fire, earthquakes, and similar events.
- Cutting and removing slots between parts of the building to be demolished, while the other part remains intact.
Modern Demolition Practices
Typical equipment used for selective demolition work include the following:
- Skid-steer loader
- Small excavator
- Robotic excavators equipped with breakers and shears
- A wide variety of attachments for skid steer loaders and mini excavators
- Aerial lifts and scissors lifts
Hand Tools used in selective demolition include the following:
- Abrasive and reciprocating saws
- Pneumatic tools such as pavement breakers and chipping guns
- Concrete saws
- Chain saws
In the past, the salvage of building materials was the primary purpose for most early demolition efforts. The term “salvage” takes several forms, and the more important types and methods of salvaging are shown below. The values of salvage sales to the demolition contractor can represent a significant portion of his or her income stream, and allow for increased competitiveness if he or she is reasonably accurate in the assessment of the salvage values for a particular job.
- Equipment Salvage: industrial buildings in particular as well as some modern commercial buildings, may contain useable equipment such as boilers, air conditioning systems, heat exchangers, tanks, electrical switchgear, motors, pumps, and a wide variety of industrial process equipment.
- Useable Materials Salvage: this category of salvage primarily includes timbers, dimensional lumber, piling, structural steel members, piping, and some types of brick.
- Scrap Metals Salvage: steel scrap produces by far the largest share of the salvage income for the demolition contractors.
- Architectural Features: these items are sometimes referred to as “historic fabric” and include any part of a building that has value. Architectural features of certain buildings that no longer have adequate commercial value are sometimes salvaged for use in the façade or interior areas of new construction.
Hazardous Material Management
The proper management of hazardous materials is important to the successful operation of a demolition project. Although the demolition contractor may not have the contractual requirement to remove and dispose of hazardous materials, it is important that they are familiar with the hazardous waste management plan in force for each project. Many of the larger demolition companies are qualified to perform hazardous materials work with their own forces, whereas other demolition firms will typically use companies that specialize in handling hazardous materials. The hazardous waste contractor may work directly for the project owner, as a sub contractor to the demolition contractor, or as a subcontractor to a general contractor.
Large buildings, industrial, smokestacks and some smaller structures can be demolished by a building implosion using explosives. The implosion of a building is completed very fast, and the collapse takes only a few seconds. Experts in this highly regulated field ensure that the building will essentially fall into its own footprint. This is very important, so as not to damage the neighboring structures. Obviously, any error can be disastrous, and some tear downs have failed and damaged neighboring structures. In addition, when a building fails to fall down completely the structure may be unstable and tilted at a severely dangerous angle–not to mention filled with explosives that have not yet detonated, making it very difficult to bring in workers to access the project safely.
Deconstruction is a newer approach to demolition with a goal to minimize material that goes into landfills. This “green” approach is accomplished by separating by material type for reuse or recycling. This type of approach and planning can result in landfill diversion rates that exceed 90% of the entire building; this process also reduces CO2 emissions compared to demolition. On very large sites, equipment is used for the segregation of waste types that can be used over in the construction of the new building. Onsite crushers take the concrete and smash it down to be reused as a Type 1 crushed aggregate, to be used either as a piling mat or for a base that is compacted into the earth below the new building, or to be used as an aggregate in concrete mix. Timber waste is shredded using equipment and then composted, or used to make timber boards like MDF or OSB. Safety is crucial on a project of this magnitude, and a safety officer is assigned to enforce all safety regulations.