14.3 Demolition: Engineering Surveys & Sequenced Removal (29 CFR 1926 Subpart T)
Key Takeaways
- 29 CFR 1926.850(a) requires a written engineering survey by a competent person, made prior to starting demolition, of the condition of the framing, floors, and walls and the possibility of unplanned collapse.
- All electric, gas, water, steam, sewer, and other service lines must be shut off, capped, or otherwise controlled outside the building line before demolition begins (29 CFR 1926.850(b)).
- No wall section more than one story in height may be permitted to stand alone without lateral bracing during masonry wall demolition (29 CFR 1926.854(a)).
- The weight of a demolition ball may not exceed 50 percent of the crane's rated load based on boom length and maximum angle of operation, or 25 percent of the nominal breaking strength of the suspending line, whichever is less (29 CFR 1926.859(b)).
- Entrances to multistory demolition structures must be protected by sidewalk sheds or canopies extending at least 8 feet from the building and capable of sustaining a load of 150 pounds per square foot (29 CFR 1926.850(k)).
14.3 Demolition: Engineering Surveys & Sequenced Removal
Demolition is a standard Optional topic in the 30-hour Construction Outreach curriculum — the four optional hours exist so trainers can cover the hazards a specific workforce actually faces, and for a demolition contractor that is 29 CFR 1926 Subpart T (1926.850 – 1926.860).
Demolition reverses the logic of every other chapter in this guide. On new construction, the structure grows stronger every day. In demolition, every hour of productive work makes the structure less stable, load paths are progressively severed, and the engineer who designed the building is not there to say which member was carrying what. That is why Subpart T opens with an engineering requirement rather than a PPE requirement.
1. The Engineering Survey — 29 CFR 1926.850(a)
"Prior to permitting employees 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."
Four elements, all testable:
| Element | Requirement |
|---|---|
| Who | A competent person |
| When | Prior to permitting employees to start demolition operations |
| What | Condition of the framing, floors, and walls, and the possibility of unplanned collapse — plus any adjacent structure where employees may be exposed |
| Documentation | The employer must have written evidence that the survey was performed |
1926.850(b): When employees are required to work within a structure that has been damaged by fire, flood, explosion, or other cause, the walls or floors must be shored or braced before work begins.
[!CAUTION] Exam Trap: the survey requires a competent person, not a registered professional engineer. Subpart T uses "competent person" here, in contrast with Subpart P, where an excavation deeper than 20 feet requires a registered professional engineer to design the protective system. Know which subpart is being asked about.
2. Utility Isolation and Hazardous Materials — 1926.850(c) through (e)
| Provision | Requirement |
|---|---|
| 1926.850(c) | All electric, gas, water, steam, sewer, and other service lines must be shut off, capped, or otherwise controlled outside the building line before demolition starts. The utility company must be notified in advance |
| 1926.850(d) | If it is necessary to maintain any power, water, or other utilities during demolition, those lines must be temporarily relocated as necessary and protected |
| 1926.850(e) | It must be determined whether any hazardous chemicals, gases, explosives, flammable materials, or similarly dangerous substances have been used in any pipes, tanks, or other equipment. Where such substances have been used, the lines and equipment must be tested and purged before demolition begins |
Outside the building line is the phrase that matters in (c). Capping a gas line inside the structure leaves live service under a building that is about to be knocked down.
Asbestos and lead
Every pre-1980 structure is presumed to contain asbestos-containing material until surveyed. Demolition triggers:
- 29 CFR 1926.1101 — asbestos in construction (Section 9.3). Demolition of thermal system insulation and surfacing ACM is Class I work with the highest control requirements.
- 29 CFR 1926.62 — lead in construction (Section 9.3). Torch cutting, burning, and abrasive blasting of lead-painted steel are the highest-exposure lead tasks in construction.
- EPA NESHAP requirements for asbestos survey and notification are separate from OSHA and run in parallel.
3. Openings, Floors, and Overhead Protection — 1926.850(f) through (k)
| Provision | Requirement |
|---|---|
| (f) | Glass that could shatter and create a fragmentation hazard must be removed |
| (g) | Wall openings at floor level must be barricaded to a height of not less than 42 inches, except where the opening is being used for material disposal |
| (h) | Floor openings not used for material disposal must be covered over with material substantial enough to support any load imposed, with the covering properly secured to prevent accidental movement |
| (i) | Where debris is dropped through openings without chutes, the area onto which the material falls must be enclosed with barricades not less than 42 inches high and not less than 6 feet back from the projected edge of the opening above. Signs warning of falling material must be posted at each level, and removal must not be permitted in this lower area until debris handling ceases above |
| (j) | All floor openings and access to the demolition area must be closed at all times except during actual passage |
| (k) | Entrances to multistory structures being demolished must be protected by sidewalk sheds or canopies, or both, providing protection from the face of the building for a minimum of 8 feet. All such canopies must be at least 2 feet wider than the building entrances or openings and capable of sustaining a load of 150 pounds per square foot |
4. Chutes — 29 CFR 1926.852
| Provision | Requirement |
|---|---|
| (a) | No material shall be dropped to any point lying outside the exterior walls of the structure unless the area is effectively protected |
| (b) | All materials chutes, or sections thereof, at an angle of more than 45 degrees from the horizontal, must be entirely enclosed, except for openings equipped with closures at or about floor level for the insertion of materials |
| (c) | A substantial gate must be installed in each chute at or near the discharge end, with a competent employee assigned to control the gate and the backing and loading of trucks |
| (d) | When operations are not in progress, the area surrounding the discharge end of a chute must be securely closed off |
| (e) | Any chute opening into which workers dump debris must be protected by a substantial guardrail approximately 42 inches above the floor or other surface on which the workers stand. Any space between the chute and the edge of openings in floors through which it passes must be solidly covered over |
| (f) | Where the material is dumped from mechanical equipment or wheelbarrows, a securely attached toeboard or bumper, not less than 4 inches thick and 6 inches high, must be provided at each chute opening |
Recall from Section 10.4 the parallel general rule at 1926.252(a): whenever materials are dropped more than 20 feet to any point lying outside the exterior walls of the building, an enclosed chute must be used.
5. Sequenced Removal — 1926.850(j), 1926.854, 1926.855
Top-down
Demolition proceeds story by story from the top down. Exterior walls and floors are removed and kept substantially level, with material dropped into designated storage areas — not accumulated on floors that were never designed for the concentrated load of demolition debris.
Masonry wall demolition — 1926.854
| Provision | Requirement |
|---|---|
| (a) | No wall section more than one story in height shall be permitted to stand alone without lateral bracing, unless the wall was originally designed and constructed to stand without such support and is in a safe condition to do so |
| (b) | Walls that serve as retaining walls to support earth or adjoining structures shall not be demolished until the earth has been properly braced or the adjoining structure has been properly underpinned |
| (c) | Walls that are to serve as retaining walls against which debris will be piled shall not be so used unless capable of safely supporting the imposed load |
Additionally, employees are not permitted to work on top of a wall when weather conditions constitute a hazard, and structural or load-supporting members on any floor must not be cut or removed until all stories above that floor have been demolished and removed.
Floor removal — 1926.855
Openings cut in a floor must extend the full span of the arch between supports. Before demolishing any floor arch, debris and other material must be removed from that arch and other adjacent floor area. Planking must be provided for workers to stand on while breaking down floor arches between beams, and safe walkways not less than 18 inches wide, formed of planks not less than 2 inches thick (if wood) or of equivalent strength material, must be provided and used by workers when necessary to enable them to reach any point without walking on exposed beams.
6. Mechanical Demolition — 29 CFR 1926.859
Wrecking-ball and mechanical demolition adds a moving multi-ton mass to an already unstable structure.
| Provision | Requirement |
|---|---|
| (a) | No workers shall be permitted in any area that can be adversely affected by demolition operations when balling or clamming is being performed. Only those workers necessary for the performance of the operations shall be permitted in this area at any other time |
| (b) | The weight of the demolition ball shall not exceed 50 percent of the crane's rated load, based on the length of the boom and the maximum angle of operation at which the demolition ball will be used, or 25 percent of the nominal breaking strength of the line by which it is suspended, whichever results in a lesser value |
| (c) | The crane boom and load line shall be as short as possible |
| (d) | The ball shall be attached to the load line with a swivel-type connection to prevent twisting of the load line, and shall be attached by positive means so that the weight cannot become accidentally disconnected |
| (e) | When pulling over walls or portions thereof, all steel members affected shall have been previously cut free |
| (f) | All roof cornices or other ornamental stonework shall be removed prior to pulling walls over |
| (g) | During demolition, continuing inspections by a competent person must detect hazards resulting from weakened or deteriorated floors, 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 |
Working the ball-weight calculation
Suppose a crane has a rated load of 60,000 pounds for the planned boom length and maximum angle of operation, and the load line has a nominal breaking strength of 90,000 pounds.
- 50% of rated load: $0.50 \times 60{,}000 = 30{,}000$ lb
- 25% of line breaking strength: $0.25 \times 90{,}000 = 22{,}500$ lb
The standard requires the lesser value, so the maximum permissible ball weight is 22,500 pounds.
[!CAUTION] The trap is picking the larger number, or averaging them. Both limits apply simultaneously and the governing one is always the smaller. Note also how this interacts with Chapter 6: the crane's rated load is read off the load chart for the boom length and operating angle in use, so a longer boom or a lower angle reduces the maximum permitted ball weight.
A demolition contractor is preparing to take down a three-story masonry commercial building damaged by fire. Under 29 CFR 1926.850, which action must occur before employees start demolition operations?
A crane with a rated load of 80,000 pounds for the planned boom length and maximum angle of operation is rigged for wrecking-ball demolition. The load line has a nominal breaking strength of 100,000 pounds. Under 29 CFR 1926.859(b), what is the maximum permissible weight of the demolition ball?
During demolition of a five-story building, laborers are dropping debris through a floor opening without a chute to a collection area on the ground. What does 29 CFR 1926.850(i) require for the receiving area?