Scaffolding questions and answers

1. Three names for the same tube
2. Standard: upright; ledger: horizontal along the scaffold; transom: horizontal across it, carrying the boards
3. Standard: brace; ledger: tie; transom: base plate
4. Standard: board; ledger: toe board; transom: guardrail

Answer: Standard: upright; ledger: horizontal along the scaffold; transom: horizontal across it, carrying the boards. Standards are the uprights, ledgers run along the face, transoms span across and support the boards. See the scaffold glossary.

More: Scaffold glossary.

1. 42 mm × 3.2 mm, 2.5 kg/m
2. 48.3 mm outside diameter × 4.0 mm wall, about 4.4 kg/m
3. 60.3 mm × 5 mm, 7 kg/m
4. 48.3 mm × 2 mm, 1.5 kg/m

Answer: 48.3 mm outside diameter × 4.0 mm wall, about 4.4 kg/m. 48.3 mm × 4.0 mm, about 4.37 kg per metre, so a 6.3 m tube is about 28 kg. BS EN 39 tube; see the free weight calculator. Verify against the latest edition.

More: Scaffold calculators.

1. Swivel coupler
2. Right-angle (double) coupler
3. Putlog coupler
4. Sleeve coupler

Answer: Right-angle (double) coupler. Right-angle couplers are the load-bearing 90° joints; swivels join at any angle (bracing), putlog couplers hold putlogs and transoms, sleeves join tubes end to end. BS EN 74-1. Verify against the latest edition.

From the free Scaffold Supervisor (EN/TG20).

1. Green: safe to use; yellow: use only with the limits on the tag; red: do not use
2. Green: being built; yellow: safe; red: inspected
3. All three mean safe
4. Colours have no meaning

Answer: Green: safe to use; yellow: use only with the limits on the tag; red: do not use. Green: inspected and safe within its limits. Yellow: limits apply, such as a harness. Red, an expired tag or no tag: do not use. GI 8.001 (2025) §9 on GCC oil and gas sites. Verify against the latest edition.

More: Tag colours.

1. It depends on the rules: OSHA 38–45 in, UK at least 950 mm, CSM II-2 0.95–1.15 m
2. Always 1.5 m
3. Always 0.8 m
4. Any height above the toe board

Answer: It depends on the rules: OSHA 38–45 in, UK at least 950 mm, CSM II-2 0.95–1.15 m. 29 CFR 1926.451(g)(4); UK Work at Height Regulations 2005 Schedule 2; CSM II-2 §2.5.4. Full comparison on the guardrail height page. Verify against the latest edition.

More: Guardrail height compared.

1. 4 m vertical, 4 m horizontal
2. 8 m vertical, 9 m horizontal
3. 12 m vertical, 12 m horizontal
4. No ties needed under 20 m

Answer: 8 m vertical, 9 m horizontal. 8 m vertically (every 4 lifts or less) and 9 m horizontally. CSM II-2 §2.5.8; other rules differ, see the tie spacing comparison. Verify against the latest edition.

More: Tie spacing compared.

1. Stationary 4 ×, mobile on casters 3 ×
2. Stationary 6 ×, mobile 5 ×
3. Any height if tied
4. 2 × for both

Answer: Stationary 4 ×, mobile on casters 3 ×. The 4:1 rule for stationary towers and 3:1 for mobile towers on casters, unless tied or the design allows more. CSM II-2 §2.9.1. Verify against the latest edition.

From the free Scaffold Inspector.

1. Classes 1 to 6: 0.75, 1.5, 2.0, 3.0, 4.5 and 6.0 kN/m²
2. Light and heavy only
3. 1 to 3: 1, 2 and 3 kN/m²
4. Every platform is 5 kN/m²

Answer: Classes 1 to 6: 0.75, 1.5, 2.0, 3.0, 4.5 and 6.0 kN/m². Class 1 is inspection only (0.75 kN/m²) and class 6 is heavy masonry storage (6.0 kN/m²). The CSM uses light, medium and heavy duty ratings in CSM II-2. See the load classes page. Verify against the latest edition.

More: Load classes compared.

1. OSHA before each shift; UK at least every 7 days and after changes or bad weather; CSM tags at most every 2 weeks
2. Once a year
3. Only at handover
4. Every 90 days

Answer: OSHA before each shift; UK at least every 7 days and after changes or bad weather; CSM tags at most every 2 weeks. 29 CFR 1926.451(f)(3); UK Work at Height Regulations 2005 Schedule 7; GI 8.001 (2025). Verify against the latest edition.

More: Inspection frequency compared.

1. Any trade that needs to
2. Only authorised scaffolders, then the scaffold is inspected and tagged again
3. The user's foreman
4. Anyone with a permit

Answer: Only authorised scaffolders, then the scaffold is inspected and tagged again. Only the scaffold crew changes a scaffold; after any change it is re-inspected before use. GI 8.001; NASC TG20:21. Record tie moves with the free tie move record. Verify against the latest edition.

More: Tie move record.

A strong answer covers:

• Tube and fitting: loose tubes joined with couplers, any shape, slower, needs skill.
• System (Ringlock, Cuplok, frames): fixed node points and set lengths, faster and repeatable, fewer shapes.
• Design rules: TG20:21 for tube and fitting, TG30:24 and the maker's data for system scaffolds in UK practice.

A strong answer covers:

• Sole boards and base plates, standards, ledgers and transoms.
• Bracing (ledger and face bracing), ties into the structure.
• Boards, guardrails, toe boards, access, and the tag.

Tip: Name them in the order you build them.

A strong answer covers:

• No tag, a red or expired tag, or a missing part (tie, guardrail, board).
• Wind over the site limit, lightning, sandstorm.
• Any change you did not expect: then report it and wait for inspection.