Performing demolition safely is a tough challenge. Two key elements in meeting it successfully are conscientious preparation, and - as with most OSHA matters - paying attention.
OSHA's demolition standards are largely (but not entirely) within 29 C.F.R. 1926, subpart T, "Demolition." Of particular importance is § 1926.850, "Preparatory Operations."
Neglecting prescribed pre-demolition measures often results in OSHA citations. Before employees are permitted to start demolition operations:
...an engineering survey shall be made, by a competent person, of the structure to determine the condition of the framing, floors, and walls, and possibility of unplanned collapse of any portion of the structure. Any adjacent structure where employees may be exposed shall also be similarly checked. The employer shall have in writing evidence that such a survey has been performed.
Identifying the presence and location of lead, asbestos, and other hazardous substances is an important part of the pre-demolition survey. If "any type of hazardous chemicals, gases, explosives, flammable materials, or similarly dangerous substances" has been used in "any pipes, tanks, or other equipment on the property," or is even suspected of being present, testing and purging must precede actual demolition. The failure to comply with this requirement is another frequently-cited OSHA violation. All utility service lines must be shut off, capped, or otherwise controlled, and the service providers notified. If any power, water, or other utilities are to be maintained during demolition, the lines must be temporarily relocated and protected.
Another key component of the survey is identifying the structure's weak points. OSHA frequently cites employers for failing to provide shoring or bracing for walls, to prevent premature collapse. Where the structure to be demolished has been damaged by fire, flood, explosion or other cause, the walls and/or floor must be shored or braced, as appropriate.
Another often-neglected precaution is the erection of an overhead shed and/or canopy to provide safe entrance into the structure to be demolished, and protection from falling objects. Any multistory building must be protected for a minimum of 8 feet from the perimeter of the building. All canopies shall be at least two feet wider than the building entrances or openings (1 foot wider on each side) and capable of sustaining a load of 150 pounds per square foot
The #1 cause of construction injuries - fall hazards - is very much present on demolition projects. Wherever a hazard exists to employees falling through wall openings, each opening must be protected to a height of approximately 42".
Since demolition operations are subject to the fall protection standards of Subpart M, note that employees on walking/working surfaces must be protected from falling through holes (a "hole" being defined as "a gap or void 2" or more in its least dimension") more than 6' above lower levels, by covers, guardrail systems, or personal fall arrest systems. Covers are required, also, to protect against objects falling through holes. Floor openings not used as material drops "shall be covered over with material substantial enough to support the weight of any load which may be imposed," the covering to be "properly secured to prevent its accidental movement."
As guardrails are a preferred means of fall protection in building interiors, you should become intimately familiar with the provisions of 29 C.F.R. § 1926.502. In addition to other, technical requirements, guardrails must be capable of withstanding, without failure, a force of at least 200 lbs., applied within 2" of the top edge in any outward of downward direction.
Access ways to the structure of the building are to be entirely closed at all times, excepting designated stairways, passageways and ladders. These must be periodically inspected, and maintained in a clean safe condition. Where a stairwell is being used in a multistory building, it must be properly illuminated, and completely and substantially covered over at a point not less than two floors below the floor on which work is being performed. Access to the floor where demolition is in progress shall be through a properly-lighted, protected, and separate passageway.
Where debris is to be dropped through holes in the floor, without the use of chutes, the area onto which the material will be dropped must be completely enclosed, with barricades not less than 42" high, and not less than 6' back from the projected edge in the opening above. Signs warning of the hazard of falling materials must be posted at each level. The removal of debris from the lower area shall not be permitted, until debris handling above has stopped.
Where chutes are employed, the chute openings must be protected by a guardrail about 42" above the floor, and any gap between the chute and the edge of openings in the floors through which it passes must be solidly covered over. Except at ground level, chute openings must be kept closed when not in use. No material may be dropped to any point lying outside the structure's exterior walls, unless the area is effectively protected. Where material is deposited into chutes by wheelbarrows or mechanical equipment, a securely-attached toeboard or bumper, at least 4" thick and 6" high, must be provided at each chute opening.
At the top of this article, I mentioned that in addition to careful preparation, "paying attention" is a major component of demolition safety. The regulations codify a number of requirements where watchfulness is needed. To cite just a few examples: "a substantial gate shall be installed in each chute at or near the discharge end. A competent employee shall be assigned to control the operation of the gate, and the backing and loading of trucks."/p>
Where floor arches are being removed, "employees shall not be allowed in the area directly underneath, and such an area shall be barricaded to prevent access to it." Notwithstanding that the lower level has been closed off, it's necessary to confirm that no one is present there, before the arch removal proceeds.
Where balling or clamming is being performed, "no workers shall be permitted in any area, which can be adversely affected." Only workers necessary for the performance of the operations may be permitted in the affected area at any other time.
As demolition proceeds, "continuing inspections by a competent person shall be made . . . to detect hazards resulting from weakened or deteriorated floors, or walls, or loosened material. No employee shall be permitted to work where such hazards exist until they are corrected by shoring, bracing, or other effective means."
Since demolition (not involving explosives) consists essentially of workers tearing down a structure from the inside, and entails many potentially hidden hazards and tons of debris being dropped through floors or chutes, it's a hazardous undertaking indeed.
In addition to observing specific regulations like the few just mentioned, you need leadership from your supervisory personnel, and trained workers who will communicate with one another, and with supervisors, regarding dangers observed.
The cost of lapses can be great. In one recent case, a bobcat collecting debris on the 19th floor of a building being demolished struck a steel beam concealed under concrete rubble. The beam was propelled through the parapet wall, causing a twenty-foor-long section of the wall to collapse into a pit outside the structure. Ordinarily, radio communications were used to ensure that no one was in the pit when work was in progress above. Unfortunately, that precaution was not carried out, and a flagger who was chatting with a driver who had backed his truck into the area to remove debris were killed when the parapet wall collapsed onto them.