Guardrails, covers, safety nets and other passive protection

Passive fall protection protects workers without any action on their part. Once a guardrail is in place or a cover is secured over a hole, it protects everyone who comes near, including visitors, inspectors, new workers and the worker who is distracted or in a hurry. That is why regulations place guardrails and covers at the top of the order of protection, after elimination. This lesson explains the main types of passive protection, the dimensions and loads they must meet, and the mistakes that defeat them.

Guardrail systems

A guardrail system is a barrier along an unprotected edge, made up of a top rail, an intermediate rail or other infill, a toe board and posts. Guardrails can be permanent, as on mezzanines and rooftops, or temporary, as on construction floors and scaffolds. Temporary systems include wood rails nailed to posts, manufactured steel or aluminum systems clamped to slab edges or weighted bases, wire rope systems and mesh panels.

Each part has a job:

• the top rail stops a worker who walks or stumbles into the edge, and must be high enough that a person's center of gravity stays on the safe side;
• the intermediate rail, mesh or screen stops a worker from slipping under the top rail, for example after falling to their knees;
• the toe board stops tools, materials and feet from sliding off the edge, protecting workers below;
• the posts transfer the loads into the structure, and their spacing and anchorage control how strong the system is.

Dimensions and loads

Look at how the strength requirements work. A guardrail must resist a worker stumbling against it, leaning on it or falling against it, and the loads are applied at the weakest point, not just at a post. Long spans between posts reduce strength, so manufactured systems specify maximum post spacing and base anchorage. A guardrail that wobbles or bends when pushed by hand probably does not meet the standard.

Where guardrails are needed

Guardrails are used at the open sides of floors, roofs, mezzanines, balconies, platforms, ramps, walkways and scaffolds, around floor openings, and at the edges of excavations and pits where people work nearby. On construction projects, perimeter guardrails are installed as each floor is formed or poured. In buildings, permanent guardrails protect rooftop equipment, roof hatches, mezzanine edges and loading areas.

Openings for deliveries need special attention. A section of guardrail removed so that a crane or forklift can land materials is one of the most common sources of falls. Use gates that close automatically, pallet safety gates that keep a barrier on the worker side at all times, or a documented procedure that keeps workers out of the area and uses restraint while the opening is unprotected, and replace the rail as soon as the landing is complete.

Choosing and installing temporary guardrails

Manufactured temporary guardrail systems have largely replaced site-built wood rails on larger projects, because they install quickly, are tested to known loads and can be reused. Common types include posts clamped to the slab edge, posts bolted or cast into the concrete, posts set in weighted bases on flat roofs, and mesh panels that combine top rail, midrail and toe board in one unit. Each system comes with instructions that set the maximum post spacing, the required slab thickness or edge distance for clamps, the weight and number of bases, and the conditions under which it may be used, such as maximum roof slope and wind speed.

Installing temporary guardrails is itself work at an unprotected edge. Plan the sequence so that installers are protected, for example by installing posts from inside the slab edge, using travel restraint anchored well back from the edge, or installing the guardrail before the formwork is stripped. Check each post as it is installed, and check the completed system before other trades are allowed near the edge. A single missing post or a clamp tightened onto a thin slab edge can turn a guardrail into a false sense of security.

Site-built wood guardrails remain common on smaller projects. They must use sound lumber of the required size, nailed or bolted to posts that are properly secured, with no protruding nails or splinters on the top rail. Wood guardrails are easy to modify, which is both their advantage and their danger: workers can remove a rail to pass materials and forget to put it back.

Rooftop guardrails and hatches

On existing buildings, permanent guardrails often protect only part of a roof: around equipment, along access routes or at hatches. Roof hatches and ladder openings are a frequent source of falls, because a worker climbing out of a hatch can step backward into the open hole, or a hatch left open can be walked into. Hatch railing systems that surround the opening with a self-closing gate solve both problems. Where rooftop equipment sits close to an unprotected edge, a short run of permanent guardrail between the equipment and the edge is usually cheaper over the life of the building than repeated temporary measures for every service call.

Protective covers

Holes in floors and roofs, including those left for stairs, shafts, ducts, pipes and skylights, must be protected by guardrails or by covers. A good cover:

• is strong enough for every load that may cross it, including workers, materials and equipment;
• is secured so that it cannot be kicked, blown or pushed out of place;
• fully covers the opening with enough bearing on each side;
• is clearly marked so that nobody mistakes it for a loose sheet of plywood and lifts it.

Covers fail in predictable ways: an unmarked sheet of plywood is picked up and used elsewhere, a cover is moved for a task and not replaced, a thin cover sags under a loaded cart, or a cover is placed over a skylight that someone assumes is solid. Some sites paint covers a bright color and stencil a warning on them, so that they stand out.

Safety nets

Safety nets catch falling workers below the work area. They are used where guardrails and personal fall arrest are impracticable, for example in bridge construction, steel erection and some roof and atrium work, and they protect several workers at once without any action on their part. Nets must be installed as close as practicable below the work surface, extend far enough beyond the edge to catch a worker who falls outward, have enough clearance below so that the net does not bottom out, and be inspected and tested.

OSHA's 1926.502(c) requires safety nets to be installed as close as practicable under the work surface and never more than 30 ft below it. Nets must extend outward from the outermost projection of the work surface by at least 8 ft when the net is up to 5 ft below, 10 ft when it is more than 5 ft and up to 10 ft below, and 13 ft when it is more than 10 ft below. Each net installation must pass a drop test with a 400 lb bag of sand 30 in in diameter dropped from the highest work surface, or be certified by a competent person. Mesh openings may not exceed 36 square inches or 6 in on any side, and debris must be removed as soon as possible and at least before the next work shift.

Other passive measures

Several other measures prevent falls without personal equipment:

• parapets of sufficient height at roof edges, which act as permanent guardrails;
• fixed walkways with handrails across roofs, linking access points to equipment;
• skylight screens and guards that can support a person;
• fencing and barricades around open pits and excavations;
• stair handrails and stair rails, covered in HSE-106;
• scaffold guardrails and platforms, covered in HSE-213;
• elevating work platforms with guardrails, covered in HSE-217.

Inspecting passive protection

Passive protection is only passive while it stays intact. Inspect guardrails and covers at the start of each shift on construction sites and after any event that could damage them: a delivery, a storm, a crane lift or a change of trades. Look for missing or loose rails, posts pulled away from the slab, toe boards removed, covers moved, unmarked or broken, and nets with tears, sagging or debris. Assign responsibility for replacing protection removed for a task, and make the person who removes it responsible for putting it back or for protecting the area until it is replaced.