Layout and quantities
Standards, ledgers, transoms and braces (rule-based estimate)
- where
- standards
- number of bays
- ledgers, counted in bay lengths
- number of lifts
- transoms per bay on a boarded lift
- bay length (m)
- maximum transom spacing for the boards (m)
- transoms
- number of boarded lifts
- braces, façade and ledger
- bays per façade brace section
- pairs of standards per ledger brace
Explain this equation
Gives a quick take-off of the main tubes in a straight independent scaffold, for pricing and loading the wagon.
Standards are two per frame line. Every bay has an inner and an outer ledger at every lift. On boarded lifts the boards need support at no more than their safe span, so each bay needs k transoms, plus one at the end of the run; unboarded lifts just need one transom per frame to hold it square. Façade braces run in sections of B_f bays, and ledger braces go at every B_l-th pair of standards, at each lift.
Counting rules applied per bay and per lift, with rounding up where a part bay still needs a component.
Sense check: 10 bays by 5 lifts with 2 boarded lifts and 2.1 m bays gives 22 standards, 100 ledger lengths, 75 transoms and 40 braces.
Watch out: real ledgers are longer tubes spanning several bays. Take the actual bracing and tie layout from the TG20 compliance sheet.
A quick take-off of the main tubes in a straight independent tied scaffold, for pricing and loading the wagon.
Enter your values to see the result.
Good to know
Rules used: two standards per frame; an inner and outer ledger in every bay at every lift; on boarded lifts, transoms at no more than the board span (1.2 m for standard 38 mm boards), so ceil(b/ts) per bay plus one at the end; on unboarded lifts, one transom at each pair of standards to hold the frame square. Façade braces: one diagonal per lift in each brace section; ledger braces: one per lift at alternate pairs of standards. Take the actual brace and tie layout from the TG20 compliance sheet. Ledgers are counted in bay lengths; in practice longer tubes span several bays and are joined with sleeve or joint pins.
Common mistake
Pricing transoms at one per bay on boarded lifts: with 38 mm boards and bays over 1.2 m you need intermediate transoms, roughly doubling the count.
Limits
Rule-of-thumb counts for a straight, uniform run. Excludes guardrails, toe boards, ties, plan bracing, ladder access, loading bays, returns and corners. System scaffolds (BS EN 12810) follow the manufacturer’s component lists. For planning and estimating only. This does not replace TG20:21 compliance (a TG20 compliance sheet or eGuide output) or a scaffold design by a competent person.
Sources
- NASC TG20:21 Good practice guidance for tube and fitting scaffolding (Operational Guide, Design Guide, User Guide and eGuide compliance sheets)
- Health and Safety Authority (Ireland), Code of Practice for Access and Working Scaffolds (sole boards ≥ 1000 cm², ties ≥ 6.1 kN, façade bracing at least every six bays, tower height to least base ≤ 3, toe-boards ≥ 150 mm)
- Properties of scaffold (steel tube 48.3 × 4.0 mm, 4.37 kg/m; 38 mm board 225 mm wide, 6 kg/m, 25 kg/m², 1.2 m max span; coupler safe working loads)
- BS EN 12811-1:2003 Temporary works equipment. Scaffolds. Performance requirements and general design (Table 3 load classes; 5.5 side protection; Annex A cladding force coefficients)
- BS EN 12810-1/-2 Façade scaffolds made of prefabricated components (system scaffolds: follow the manufacturer’s design data)
Results are calculations from the published methods and figures shown, and depend on the data you enter. For planning and checking only. Scaffolds must be erected to NASC TG20 or a bespoke design by competent persons, and lifting operations planned under LOLER by a competent person. Never rely on these results instead of a design, a lift plan or manufacturer ratings.