A “qualified person” is responsible for designing a scaffold under federal safety regulations. OSHA defines a qualified person as someone who holds a recognized degree, certificate, or professional standing, or who has demonstrated through extensive knowledge, training, and experience the ability to solve problems related to scaffold design. For certain scaffold types and heights, the requirement goes further: only a registered professional engineer can do the design work.
What “Qualified Person” Actually Means
OSHA’s construction standards require that every scaffold be designed by a qualified person and then constructed and loaded according to that design. This isn’t a loose suggestion. The qualified person must be able to demonstrate their ability to solve design problems specific to the project, whether through formal credentials or proven hands-on expertise. In practice, this often means someone with engineering training or years of specialized scaffold experience.
The key distinction is between a qualified person and a competent person, two terms OSHA defines separately. A competent person is someone on the job site who can identify hazards and has the authority to correct them immediately. They oversee erection, inspection, and daily use of the scaffold. A qualified person handles the upfront design work: selecting the scaffold type, calculating loads, and specifying how the structure should be built. One person can fill both roles if they meet both sets of criteria, but they serve different functions.
When a Professional Engineer Is Required
For standard scaffolds at moderate heights, a qualified person without a formal engineering license can handle the design. But once a scaffold exceeds certain thresholds or involves specific configurations, OSHA requires a registered professional engineer to take over. These situations include:
- Pole scaffolds over 60 feet in height
- Tube and coupler scaffolds over 125 feet in height
- Fabricated frame scaffolds over 125 feet above their base plates
- Scaffolds that move while workers are on them
- Outrigger scaffolds and their components
- Brackets on fabricated frame scaffolds that support cantilevered loads beyond just workers
- Masons’ multi-point adjustable suspension scaffolds, where the direct connections must be designed by an engineer experienced in that specific type of scaffold
These thresholds exist because the engineering demands increase sharply with height, complexity, and the consequences of failure. A scaffold moving with workers aboard, for instance, introduces dynamic loads that require formal structural analysis.
Load Capacity Requirements the Designer Must Meet
Whoever designs the scaffold must account for strict safety factors built into the regulations. Every scaffold and scaffold component must support its own weight plus at least four times the maximum intended load without failure. That means if a platform will carry 1,000 pounds of workers and materials, it needs to hold 4,000 pounds before anything gives way.
Suspension ropes carry even higher requirements. Ropes on non-adjustable suspension scaffolds must handle six times the maximum intended load. Adjustable suspension scaffold ropes also need to support six times the load, calculated against either the rated capacity of the hoist or twice the stall load, whichever produces the greater demand. Counterweights and direct roof or floor connections must resist at least four times the tipping moment at the rated hoist load.
These safety factors aren’t optional design targets. They’re regulatory minimums, and the designer is the person accountable for ensuring the scaffold meets them before a single worker steps onto the platform.
Suspended Scaffolds Have Extra Design Rules
Suspended scaffolds, the kind that hang from a building rather than standing on the ground, get additional design scrutiny. Platforms on two-point suspension scaffolds can’t be wider than 36 inches unless a qualified person specifically designs them to prevent tipping or instability. Masons’ multi-point adjustable suspension scaffolds require their connections to be designed by an engineer with direct experience in that scaffold type, not just any registered professional engineer.
This distinction matters because suspended scaffolds introduce risks that supported scaffolds don’t. The attachment points to the building, the rope systems, and the counterweight calculations all demand specialized knowledge. A design error doesn’t just cause a collapse at ground level; it can mean a platform falling from significant height.
What the Design Documentation Looks Like
A proper scaffold design isn’t just a verbal plan. In many jurisdictions, detailed drawings must be available at the project site. New York City’s requirements offer a useful example of what thorough documentation includes: site and plot plans showing the scaffold location relative to the building and surrounding streets, detail drawings of structural support and connections, anchorages, tie-ins, and tie-backs, platform levels with maximum loads for each level, and the number of levels that can be loaded at the same time.
For suspended scaffolds, the documentation should specify rope configurations, the number of clips, counterweight calculations, and outrigger beam details. For supported scaffolds, it needs to show structural members and how the scaffold is founded, whether on a sidewalk shed, floor, roof, or ground. Any changes to the design during the project must be reflected in revised drawings signed and sealed by the design professional.
The industry consensus standard, ANSI/ASSP A10.8-2019, supplements OSHA’s requirements with additional guidelines covering erection, use, and dismantling across scaffold types ranging from suspended and adjustable scaffolds to pump jack scaffolds and portable work stands. It also includes guidance on surveying the job site and calculating allowable stress for wood scaffold planks.
Where Employer Responsibility Fits In
The employer controlling the work site holds the ultimate legal obligation to ensure the scaffold was designed by a qualified person and built according to that design. This doesn’t mean the employer personally designs the scaffold. It means the employer must hire or designate someone who meets the qualified person standard, verify that the design meets OSHA’s capacity and safety factor requirements, and ensure the scaffold is erected to match the design specifications. If a scaffold fails and it turns out no qualified person was involved in the design, the employer faces OSHA citations and liability for any injuries.
The competent person on site then takes over daily responsibility: inspecting the scaffold before each shift, checking for damage or changes in conditions, and making sure workers use the scaffold as it was designed to be used. Design and supervision are two separate layers of protection, and the regulations treat them that way.