Portable ladder types, ratings and selection

Choosing the right ladder prevents many incidents before they start. A ladder that is too short tempts people to stand on the top steps. A household ladder on a construction site may be overloaded. An aluminum ladder near live electrical parts can conduct current through the user. This lesson describes the main types of portable ladder, how load ratings work, how material affects safety, and how to select a ladder for a task.

The main types of portable ladder

Portable ladders fall into two broad groups. Self-supporting ladders stand on their own: stepladders, platform ladders, trestle ladders and some multi-position ladders in their A-frame configuration. Non-self-supporting ladders must lean against a structure: single straight ladders and extension ladders.

• Stepladder: an A-shaped, self-supporting ladder with flat steps on the front and a rear section that may or may not have steps. Spreader bars lock the two sections open. Stepladders are meant to be used fully open, on a level surface, facing the steps.
• Platform ladder: a stepladder with a large standing platform near the top, usually with a guardrail or knee rail around it. It is a better choice than a stepladder for work that takes more than a few minutes, because the user stands on a wide surface with support at waist or knee height.
• Extension ladder: two or more sections that slide within each other and lock with rung locks, raised with a rope and pulley or by hand. Extension ladders reach higher than any stepladder and are the standard way to reach roofs and upper floors.
• Single or straight ladder: one section with no adjustment. Often used as a fixed-length access ladder or in confined areas.
• Multi-position or articulated ladder: a ladder with locking hinges that can be configured as a stepladder, an extension ladder, a scaffold base or a stairway ladder. Versatile, but every configuration and lock must be set correctly.
• Trestle and extension trestle ladders: pairs of self-supporting sections used to support planks for low-level work.
• Telescoping ladders: compact ladders whose rungs collapse into each other. They are convenient for transport but have more locking points to inspect.
• Mobile ladder stands and rolling platforms: wheeled steps with handrails, common in warehouses and stores, which lock when weight is applied.

Load ratings: grades and duty types

Every ladder is designed for a maximum load. That load includes the user, their clothing and protective equipment, and everything they carry: tools, materials and supplies. Overloading a ladder can cause rails to buckle, rungs to bend and joints to fail.

In the United States, ANSI A14 standards classify portable ladders into duty types. OSHA accepts ladders built to these standards, and the duty type must be marked on the ladder.

Construction and industrial employers normally use Type I, IA or IAA ladders. Type III household ladders are not appropriate for work, even for light tasks, because their margins are smaller and they are not built for daily use.

Ladder materials

Portable ladders are made of wood, aluminum or fiberglass. Each has strengths and weaknesses.

Never paint a wooden ladder with an opaque finish. Paint hides cracks, splits and rot. A clear sealer or preservative is acceptable. Fiberglass ladders exposed to sunlight for years develop fiber bloom, a powdery surface with exposed glass fibers, which reduces their strength and electrical resistance; manufacturers describe when to retire them.

Ladders and electricity

Metal ladders conduct electricity. OSHA's 1926.1053(b)(12) requires ladders to have nonconductive side rails if they are used where the user or the ladder could contact exposed energized electrical equipment. In general industry, 1910.333(c) requires unqualified workers and their conductive objects, including ladders, to stay at least 10 ft from overhead lines up to 50 kV, with more distance for higher voltages. Even fiberglass and wood can conduct if they are wet, dirty or contaminated.

Choosing the right length

A ladder must be long enough for the job without standing on the top steps or rungs. For stepladders, manufacturers mark the top cap and often the step below it as not to be stood on, so the highest standing level is two steps from the top. A useful rule is that a person can reach about 1.2 m above their standing level comfortably. For extension ladders, the ladder must be long enough to reach the support at the correct angle, extend above the landing if it is used for access, and allow the required overlap between sections.

Other selection factors

• Duration: for tasks longer than a few minutes, a platform ladder, rolling tower or scaffold is better.
• Surface: stepladders need firm, level ground; leveling devices or ladder mats help on slightly uneven ground; a scaffold may be better on rough ground.
• Space: in narrow aisles a platform ladder with a small footprint may be the only option; in doorways, lock or guard the door.
• Weather: wind can blow over stepladders and extension ladders outdoors; ice and snow need special feet or a different access method.
• Frequency: permanent stairs or fixed ladders are better where access is needed every day.
• Accessories: stand-off arms keep an extension ladder clear of gutters and give a wider top support; levelers and spurs help on slopes and soft ground; tool trays keep hands free.

Building a ladder fleet

Many employers manage ladders as a fleet rather than letting each crew buy its own. A small set of standard ladder types makes training, inspection and replacement simpler. A typical fleet for a maintenance department might include platform ladders of two or three heights for most indoor tasks, fiberglass extension ladders for roof access and electrical work, a few stepladders for quick jobs, and one or two rolling towers for longer work. Each ladder is numbered, assigned to a location or crew, and entered in the inspection log.

When buying ladders, look for:

• the correct grade or duty type for the heaviest expected user and load;
• fiberglass rails wherever electrical work is possible;
• slip-resistant steps and feet suited to the floors where the ladder will be used;
• platform ladders with guardrails for tasks over a few minutes;
• accessories such as stand-offs, levelers and tool trays from the same manufacturer;
• clear labels and instructions in the languages workers read.

Ladders for specialized environments

Some environments need special ladders. Clean rooms and food plants may need stainless steel or easily cleaned ladders. Areas with flammable atmospheres may need non-sparking ladders and accessories. Warehouses use rolling ladders with locking casters and handrails for picking from racks. Utilities and telecommunications crews use dielectric ladders tested for electrical work. Fire departments and rescue teams use ladders built to their own standards. In each case, the manufacturer's rating and instructions must match the use.

Whatever fleet you buy, train every user on the specific models, because locks, spreaders and hinges differ between manufacturers.

Finally, retire ladders that are damaged, unlabeled or of unknown grade, and replace them with ladders from the fleet list. Mixed collections of old ladders bought over many years are a common source of defects and confusion about ratings.