The requirements below come from Ontario Regulation 213/91 (Construction Projects) under the Occupational Health and Safety Act (OHSA), specifically Part III — Scaffolds, sections 125 through 141. These are the rules a Ministry of Labour inspector enforces when they see a scaffold on your construction project.
Scaffold collapses and falls from scaffolds are among the leading causes of serious injuries and fatalities on Ontario construction sites. A scaffold is not permanent infrastructure — it is a temporary structure that is assembled, modified, and dismantled repeatedly over the life of a project. Every time a scaffold is changed, the risk profile changes. A brace left out, a pin not inserted, a plank that has cracked under repeated loading, a base plate sitting on frozen ground that thaws in the afternoon — any of these can cause a catastrophic failure. The inspection requirement exists because scaffolds degrade. They get hit by equipment. Workers remove planks to pass materials through and forget to replace them. Wind loads shift components overnight. The regulation requires inspection by a competent person before each shift and after any event that could affect structural integrity. This is not a formality — it is the last line of defence between a functional scaffold and a collapse that sends workers to the ground.
Sections 125 and 127 of O. Reg. 213/91 require that scaffolds be designed and erected under the supervision of a competent person. Under OHSA, “competent” means a person who is qualified because of knowledge, training, and experience to organize the work and its performance, is familiar with the Act and regulations that apply, and has knowledge of any potential or actual danger to health or safety in the workplace. For scaffold work, this means someone who understands the manufacturer’s instructions for the specific scaffold system being used, knows the load capacities of each component, can identify defective materials, and understands the tying and bracing requirements. A labourer who has never been trained on scaffold erection is not a competent person — even if they have watched others do it for years. The constructor and employer are liable if they allow an incompetent person to supervise scaffold work and a failure occurs.
Section 128 requires that every scaffold be erected on a firm foundation. This sounds simple but it is where the majority of scaffold collapses originate. A firm foundation means mudsills (typically 2x10 or 2x12 lumber) under the base plates, distributing the scaffold load over soft ground. Concrete, compacted gravel, and asphalt are adequate — but freshly backfilled soil, thawing ground, and rain-softened clay are not. The regulation explicitly prohibits makeshift supports — concrete blocks, stacked bricks, scrap lumber — under scaffold legs. Base plates must be in full contact with the mudsill and the scaffold must be plumb and level. A scaffold that is 2 degrees out of plumb at the base can be 150 mm or more out of plumb at working height on a 10-metre scaffold, and that eccentricity multiplies the lateral forces on the structure. Inspectors carry levels.
Section 131 requires that a scaffold be capable of supporting at least 4 times the maximum load to which it is likely to be subjected. This is not 4 times the weight of the workers — it is 4 times the total of workers, tools, materials stored on the platform, and any dynamic loads from work activity (pouring concrete, lifting materials, wind). A standard frame scaffold bay with two 10-inch aluminum planks can typically support 75 pounds per square foot, but that capacity drops dramatically if a plank is cracked, a frame leg is bent, or cross-bracing is missing. The safety factor exists because real-world conditions are never ideal — components wear, loads are estimated, and workers sometimes stack more material on a platform than planned. When a scaffold is loaded to its rated capacity with a 4:1 safety factor, it has a 75% reserve. When workers pile extra material and reduce that factor to 2:1, the scaffold is one unexpected load away from failure.
Section 26.3 of O. Reg. 213/91 requires guardrails on all open sides of a scaffold platform where the height is 2.4 metres (7.9 feet) or more. The guardrail must include a top rail between 0.9 m and 1.1 m above the platform, a mid rail, and a toe board at least 89 mm high. Section 130 requires that platform planks be at least 460 mm (18 inches) wide and that gaps between planks not exceed 25 mm (1 inch). A 50 mm gap between planks is wide enough for a tool to fall through and strike a worker below — or for a worker’s foot to catch during movement. Fully decking the platform and securing planks against displacement are not optional — they are regulatory requirements with serious consequences when ignored.
Section 134 covers rolling or mobile scaffolds. The most dangerous moment in a rolling scaffold’s use is during movement. The regulation prohibits workers from remaining on the platform while the scaffold is being moved. This rule exists because even a small bump or crack in the floor surface can cause a sudden stop, and the resulting lateral force at platform height — amplified by the scaffold’s height — can throw a worker off the platform. Casters must be rated for the full scaffold load and wheel brakes must be engaged whenever work is being performed. When the scaffold height exceeds 3 times the minimum base dimension, outriggers or stabilizers must be deployed to prevent tipping. The floor surface must be smooth, level, and free of holes, drop-offs, or debris.
Sections 136 through 141 govern suspended scaffolds (swing stages). These are among the most dangerous scaffold types because the entire structure hangs from the building by wire ropes, and a single rope failure can be catastrophic. Every suspended scaffold must be designed by a Professional Engineer, regardless of height or size. The PE drawings must be on site. Wire ropes must have a 10:1 safety factor — far higher than the 4:1 required for frame scaffolds — because dynamic loading, rope wear, and environmental degradation (UV, chemicals, abrasion over parapet edges) reduce rope strength over time. Each worker must have an independent safety line connected to a separate anchor from the scaffold suspension system. If the scaffold fails, the worker’s independent lifeline catches them. The roof rigging must be inspected by a competent person before each use. The platform must remain level within 3 degrees — a tilted swing stage means uneven loading on the suspension points and worker instability.
Section 14 of O. Reg. 213/91 requires that any scaffold taller than 15 metres (approximately 49 feet) must be designed by a Professional Engineer licensed in Ontario. The PE must produce drawings specifying the scaffold configuration, component types, bracing intervals, tie-in locations, and maximum load capacity. Those drawings must be on site and the scaffold must be erected per the PE’s specifications exactly — field modifications by the crew are not permitted without the PE’s approval. The 15-metre threshold exists because the engineering complexity of a tall scaffold increases non-linearly. Wind loads, eccentric loading, thermal expansion, and the cumulative effect of component tolerances all become significant at height. A 6-metre scaffold can often be designed from the manufacturer’s standard tables. A 20-metre scaffold requires site-specific engineering that accounts for the building geometry, wind exposure, soil conditions, and the specific work being performed.
Scaffold violations are among the most common orders issued by Ministry of Labour inspectors on Ontario construction sites. An inspector who finds a scaffold with missing braces, no guardrails, workers without Working at Heights training, or a scaffold over 15 metres without PE drawings will issue a compliance order — and in most cases, a stop-work order under OHSA section 57 that halts all scaffold-related activity until the violations are corrected. Fines under OHSA section 66 can reach $100,000 and 12 months imprisonment for an individual, or $1,500,000 for a corporation. In 2023, scaffold-related violations accounted for hundreds of Ministry of Labour orders across the province. Beyond fines, a scaffold collapse that injures or kills a worker triggers a WSIB lost-time claim that affects the employer’s experience rating and premiums for years. For a small contractor with $500,000 in annual payroll, even one serious scaffold claim can increase WSIB premiums by $10,000 to $30,000 per year for 3 to 5 years. The cost of proper inspection — 10 minutes per shift by a competent person — is negligible by comparison.