Advanced Scaffolding (SA) flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Design load classes

Light duty is 2.0 kN/m², medium duty 2.5 kN/m², and heavy duty 3.0 kN/m². The class determines platform width, transom spacing, and tie density.

Ground bearing pressure

Total leg load divided by the effective base plate area. A 150 mm square plate covers 0.0225 m², so a 10 kN leg load gives about 444 kPa, which must be below soil capacity.

Minimum platform width

A working platform must be at least 600 mm wide. Platforms of 450 mm (two boards) are for access only and must not be used as a work area.

Overhead line clearance

Scaffolds must stay at least 3.5 m horizontally from overhead lines up to 66 kV. Higher voltages need utility coordination and a written permit before erection begins.

Guardrail dimensions

Top rail sits 950–1100 mm above the platform, a mid-rail at about half height, and a toe board at least 150 mm high to stop tools and material sliding off.

Excavation setback rule

The scaffold base should be set back from an excavation crest by at least the excavation depth, unless a geotechnical assessment shows the soil can carry the leg loads safely.

Public protection zone

Where material could fall onto a pedestrian route, provide fan netting or a protected walkway. The exclusion width equals scaffold height plus the dropped-material fall radius.

Tie spacing rule

For standard independent tied scaffolds, ties are placed at vertical intervals of 4 m or less and horizontal intervals of 6 m or less. Ties resist wind uplift and pull-off as well as compression.

Bracing pattern

Ledger (zig-zag) bracing goes in every alternate bay and at both ends. Facade bracing runs continuously to the top, with a longitudinal bracing bay at 30 m maximum centres.

Wind drag on tube

Wind force on open tube is about 0.7 × dynamic pressure × projected area. Adding netting or sheeting multiplies this force several times, so ties must be recalculated.

Standard tube dimensions

Scaffold tube is 48.3 mm outside diameter with a 3.2 mm nominal wall (4.0 mm for heavier duty) and yield strength of 235–355 MPa. Never mix diameters in one member.

Right-angle coupler capacity

A correctly torqued right-angle coupler (40–50 N·m) carries roughly 6–7 kN slip capacity. Swivel couplers are lower and must not be the sole connection for a load-bearing tie.

Cantilever anchorage moment

The design moment at the anchorage equals the suspended load times its lever arm, plus scaffold self-weight. Counterweights must be calculated and positively fixed, never loose.

Free-standing tower ratio

A free-standing tower is limited to a base-to-height ratio of about 1:3. Outriggers extend this to about 1:4. Beyond that, the tower must be tied to a structure.

Load path chain

Platform load travels to transoms, then ledgers, then standards, then base plates, then ground. A missing transom or unbraced standard breaks the chain and concentrates load.

Erection sequence

Build bottom-up in complete lifts: base, standards, ledgers, transoms, platform, then guardrails. No lift may be left without guardrails before the next lift starts.

Progressive tie installation

Ties go in as the scaffold rises. A scaffold more than 2 m above a tie level without ties may not stand overnight without a documented assessment.

Dismantling order

Dismantle top-down, the reverse of erection. Keep ties in place until the lift below is removed, and lower tubes with a gin wheel or chute rather than dropping them.

Competent person rule

Erection, alteration, and dismantling require training and assessment for that specific scaffold type. Untrained alteration, such as removing a guardrail, is a leading incident cause.

Gin wheel capacity

A gin wheel is typically rated 250 kg with 500 kg rope. It must be fixed to a standard with a positive fixing, not a single coupler, and never overloaded.

Ladder access rules

Ladder stiles extend 1 m above the landing, the ladder sits at 75° (1 in 4), and it is tied at intervals of no more than 9 m along its length.

Alteration assessment

Adding a platform level, sheeting, or a hoist changes the load path. Any alteration must be checked against the original design before work proceeds.

Weather hold points

Stop erection or dismantling when wind exceeds the manufacturer's limit (commonly 17 m/s), during lightning, or when ice forms on tube surfaces.

Inspection frequency

Inspect before first use, after any alteration, after any event affecting stability, and at least every 7 days while the scaffold remains in use.

Inspection record contents

Record date, time, location, load class, findings, corrective action, and inspector name and signature. Retain for the scaffold's life plus the statutory period.

Tagging system

Red tag means do not use (missing ties, guardrails, or base plates). Amber means restricted use for minor damage. Green means safe after a full check.

Point load spreading

Never exceed the duty class. A concentrated load such as a brick stack must be spread over at least two boards or placed on a load-spreading plate.

Tube rejection criteria

Discard tubes bent more than 5 mm per metre, cracked, or with corrosion loss over 10% of wall thickness. Damaged components are replaced, not repaired.

Fall protection for inspectors

A scaffold is not fall protection for the people inspecting it. Inspectors use the same fall-arrest system as erectors, with anchorage points verified before climbing.

Suspension trauma rescue

A suspended worker must be rescued within about 15 minutes. Harness suspension restricts blood flow, so prompt rescue is a life-safety requirement, not a convenience.

Housekeeping rule

Keep platforms free of loose material and debris. Overlapping boards need positive fixing, and accumulated debris can blow off or overload the platform.

Load rating verification

Before loading, confirm the scaffold's rated duty class matches the intended task and that ties, bracing, and base plates are all in place for that class.