Scaffolding Setup & Safety

A scaffold is a temporary raised work platform. Set up right, it is the safest way to work at height for hours at a time. Set up wrong, it can tip, rack or drop a plank, and everyone on it falls at once. Masons, painters, insulators, sheet metal workers, plasterers and many others work from scaffolds, so most of this applies whether you build them or only stand on them.

In US construction, scaffolds fall under OSHA 29 CFR 1926 Subpart L. Section 1926.451 has the general rules, 1926.452 covers specific scaffold types, and 1926.454 covers training. States with their own OSHA plans can be stricter. Always follow the manufacturer's instructions as well. Reading this does not qualify you to erect a scaffold. OSHA requires training by a qualified person for anyone who erects, moves, dismantles, inspects or works on one.

What You Will Be Able to Do

• Name the common scaffold types and where each is used.
• Check a scaffold's base, ties, planking, guardrails and access against the rules.
• Work out what a platform can safely hold.
• Tell a competent person's job from a worker's job.
• Decide when to stay off a scaffold.

Who Does What

• Competent person. Can identify scaffold hazards and has the authority to correct them right away. Must supervise erecting, moving, dismantling and altering, and must inspect the scaffold before each work shift and after anything that could affect it, such as a storm or an impact.
• Qualified person. Has a degree, certificate or extensive experience that proves they can solve scaffold problems. A qualified person must design every scaffold.
• Registered professional engineer. Must design fabricated frame scaffolds over 125 feet above their base plates. Anything built past the manufacturer's limits also needs an engineered design.
• Worker. Uses the scaffold as built, does not change it, and reports damage. If you need a brace moved or a plank pulled, ask the competent person.

Common Scaffold Types

Setting a Safe Base

Everything above depends on the base. OSHA requires footings to be level, sound, rigid and able to hold the loaded scaffold without settling or moving.

1. Look up and down. Check for overhead power lines, doors, equipment and anything buried below.
2. Check the ground. Avoid fill, frozen ground that may thaw, and any spot where water will run under the legs.
3. Lay mudsills. A mudsill is a plank that spreads the leg load over the ground. Timber such as a 2x10 is common. On soft ground, a common practice is to run sills at least 2 feet past the scaffold on each side.
4. Set base plates and screw jacks. Every leg sits on a base plate. Screw jacks handle small differences in grade. Many manufacturers limit jack extension to about 12 inches. Check the label.
5. Never level with scrap. Do not stack blocks, bricks, or loose boards under a leg. Unstable objects may not support scaffolds or planks.

Building a Frame Scaffold

These are the normal steps for a frame scaffold. Other types follow their own manufacturer's sequence.

1. Set the first two frames on the base and install cross braces.
2. Check plumb and level in both directions before adding anything else. A small lean at the bottom grows with every tier.
3. Pin frames together vertically with coupling pins. Lock them with pins where wind or use could lift them apart.
4. Plank each level as you go, so erectors always have a platform.
5. Add ties as the scaffold rises, not at the end.
6. Add guardrails and access before anyone else goes up.

Erectors do not always have guardrails to work behind. OSHA requires the competent person to decide whether fall protection is feasible and safe for each erecting or dismantling job, and to provide it where it is.

Planks and Platforms

• Fully planked. The platform must be fully decked between the front uprights and the guardrail supports. Gaps between planks can be no more than 1 inch. Where a wider gap is truly needed around uprights, the open space may not exceed 9-1/2 inches.
• Width. At least 18 inches for most scaffolds. A few types, such as pump jack and ladder jack, allow 12 inches.
• Distance from the work. The front edge must stay within 14 inches of the work face, unless guardrails or fall arrest protect that side.
• Overhang. Unless cleated or hooked, each end must extend at least 6 inches past the centerline of its support. A plank 10 feet or shorter may overhang no more than 12 inches, and a longer plank no more than 18 inches, unless it cannot tip or guardrails block access.
• Overlaps. Overlap only over a support, by at least 12 inches, unless planks are nailed or otherwise restrained.
• Plank grade. Use only scaffold-grade or manufactured planks. Cull any plank that is cracked, split or badly warped. A loaded plank may not bend more than 1/60 of its span.
• Clear decks. Debris cannot pile up on platforms. Clear ice, snow and mud before use.

Ties and Stability

A scaffold that is tall for its width can tip. OSHA requires any supported scaffold with a height-to-base-width ratio over 4 to 1 to be held by guys, ties or braces. A scaffold with a 5-foot-wide base reaches that limit at 20 feet.

• Place the first tie at the closest horizontal member to the 4-to-1 height.
• Repeat every 26 feet or less going up for scaffolds wider than 3 feet, and every 20 feet or less for scaffolds 3 feet wide or narrower.
• Keep the top tie within the 4-to-1 height of the top.
• Place ties at each end and no more than 30 feet apart along the length.
• Ties must hold the scaffold both in and out from the wall. Never cut a tie to make room for your work. Ask the competent person.

Wind loads, enclosures and hoists change the math. Scaffolds with tarps or sheeting catch wind like a sail, so they need a design that accounts for it.

Guardrails and Falling Objects

Fall protection is required on a scaffold more than 10 feet above a lower level. That is different from the 6-foot trigger for most other construction work. The type depends on the scaffold.

For scaffolds placed in service after January 1, 2000:

• Top rail: 38 to 45 inches above the platform. It must hold at least 200 pounds on most scaffolds.
• Midrail: about halfway between the top rail and the platform.
• Toeboard: at least 3-1/2 inches high. It protects people below from falling objects, and it is required where tools or material could fall on them. Debris nets, screens or barricades may also be needed.

Do not use a cross brace as a toprail or midrail unless it crosses at the heights OSHA allows. Everyone working around a scaffold wears a hard hat. If you tie off on a suspended scaffold, your lifeline must be independent of the scaffold's support ropes, so that one failure cannot take out both.

Warning: Never remove a guardrail to pass material through without a plan to protect the opening. If you take off a rail, you have made a fall hazard, and you are the one standing next to it.

Safe Access

A platform more than 2 feet above or below the access point needs a proper way on and off. Use a built-in frame ladder, an attached ladder or a stair tower. Stair towers are best for heavy traffic or when people carry tools.

• Never climb cross braces. OSHA prohibits it.
• Keep both hands free. Haul tools and material up by rope or hoist.
• Do not use a ladder, box or bucket on a platform to gain height. The only exception is on large area scaffolds that meet specific OSHA conditions.

Load Ratings

Each scaffold must hold its own weight plus at least 4 times the maximum intended load. In practice, you work from the rating on the tag or the manufacturer's data. OSHA's non-mandatory guidelines describe these duty classes:

Worked example. A platform bay is 5 feet by 7 feet, which is 35 square feet.

• Light duty: 35 x 25 = 875 pounds.
• Medium duty: 35 x 50 = 1,750 pounds.

Now count what is really up there on the medium-duty bay. Two people with tools at about 250 pounds each is 500 pounds. Forty 8-inch concrete blocks at about 35 pounds each is 1,400 pounds. The total is 1,900 pounds, so the bay is over its rating. Take off at least 5 blocks.

The rating covers everything on the platform: people, tools, material and debris. Spread material out rather than stacking it in one spot. If there is no tag or you cannot tell the rating, treat it as light duty and ask before you load it.

Power Lines

Keep every part of the scaffold, the materials and the people clear of power lines. That includes while you are moving the scaffold or carrying long tubes.

Treat every line as live and uninsulated unless the utility confirms otherwise. If you cannot hold the clearance, the utility must de-energize, move or shield the line before work starts.

Rolling Scaffolds

• Use only on a firm, level floor. Keep clear of holes, ramps and floor edges.
• Lock casters any time the scaffold is in use, not just when you notice it rolling.
• Clear the platform of tools and material before moving it.
• As a rule, stay off the scaffold while it moves. OSHA allows riders only when strict conditions are met, including a floor within 3 degrees of level and free of holes, a height no more than twice the base width, and outriggers on both sides.
• Push from as close to the base as you can, no higher than 5 feet above the floor.

Suspended Scaffolds

Suspended scaffolds need extra training and their own inspection routine. Three rules stand out:

• Counterweights must be made for that purpose and mechanically fastened to the outrigger beam. Sand, gravel, water and other material that can shift or flow are not allowed, and neither are construction materials such as masonry units.
• Each worker on a single-point or two-point scaffold needs both a guardrail and a personal fall arrest system.
• A competent person checks ropes and rigging before each shift.

Before You Step On

The competent person's inspection does not replace your own look. Take 30 seconds:

• Is there a green tag, or whatever your site uses to show it passed inspection today?
• Are the legs on plates and sills, with nothing undermined?
• Are all braces and pins in place?
• Is the platform fully planked, with no cracked boards?
• Are guardrails on every open side?
• Is there a proper ladder or stair?

If a scaffold is unsafe, tag it DO NOT USE, keep people off, write down the defect and report it. It stays out of service until repaired and re-inspected.

Weather

Do not work on a scaffold in a storm or high wind unless the competent person decides it is safe and everyone is protected by fall arrest or wind screens. OSHA sets no specific wind speed for supported scaffolds, so follow your site's limit. Get off at the first sign of lightning. Clear ice and snow before anyone climbs.

Taking It Down

Dismantle in the reverse order of erecting, from the top down. That keeps the scaffold stable at each stage.

1. Check that the scaffold has not been changed. Look for missing ties or braces first.
2. Work one tier at a time. Do not remove a tie until the scaffold has been brought down to that level.
3. Lower parts by hand line or hoist. Never throw them.
4. Keep the area below barricaded.
5. Sort and tag damaged parts so they are not used again.

Common Mistakes

Check Your Understanding

1. A frame scaffold has a 4-foot base. How tall can it go before it must be tied?

16 feet, because 4 feet x 4 = 16 feet. Past that, it needs ties, guys or braces.

2. You are on a platform 12 feet up and the guardrail on one end is missing. What now?

Get off that end and report it. At more than 10 feet you need a guardrail or fall arrest. The competent person must correct it before work continues.

3. A plank extends 15 inches past its support and it is 8 feet long. Is that acceptable?

Not unless it is built so that it cannot tip, or guardrails block access to the overhang. A plank 10 feet or shorter may overhang no more than 12 inches.

4. You find a rolling scaffold with one caster unlocked. Does it matter if you are only going up for a few minutes?

Yes. Casters must be locked whenever the scaffold is in use. Lock all of them first.

5. A crew wants to use the top of a scaffold as an anchor for fall arrest. Who decides?

The competent person, using the manufacturer's data. Most scaffolds are not designed for fall arrest loads unless the manufacturer or an engineer says so.

Key Takeaways

• A competent person supervises every change and inspects before every shift.
• Use firm footing, base plates and mudsills. Never level with scrap.
• Scaffolds taller than 4 times their base width must be tied.
• Fall protection is required more than 10 feet above a lower level.
• Know the load rating, and count people, tools and material.
• Use the ladder or stairs, never the cross braces.
• If something looks wrong, tag it, stay off and report it.