Tube and fittings
Fittings count estimate (BS EN 74 couplers)
- where
- standards
- number of bays
- double (right-angle) couplers
- number of lifts
- spares allowance (%)
- putlog or single couplers
- number of transoms
- swivel couplers
- number of braces
- joint pins or sleeve couplers
- length of each standard line (m)
- stock tube length (m)
- bay length (m)
Explain this equation
Gives a rule-based count of the main couplers for a straight independent scaffold, to order fittings and price the job.
A double coupler fixes each ledger to each standard: every standard at every lift. Each transom needs two putlog or single couplers, and each brace two swivels. Joints are needed where a standard is taller than one stock tube, and in each of the two ledger lines at every lift where the run is longer than a stock tube; the number of joints is the number of tubes in the line less one. The spares percentage is added and each count rounded up.
Counting rules: one fitting per connection, two per tube end where a tube is fixed at both ends.
Sense check: 10 bays by 5 lifts gives 110 doubles, 150 putlogs for 75 transoms, 80 swivels for 40 braces and about 52 joints.
Watch out: add tie fittings, guardrail couplers, toe board clips and base plates separately.
A rule-based count of the main couplers for a straight independent scaffold, to order fittings and price the job.
Enter your values to see the result.
Good to know
Rules: one double coupler where each ledger crosses each standard; two putlog or single couplers per transom (some designs fix node-point transoms with double couplers, so move those across); two swivels per brace; joints in standards and in each ledger line where it is longer than a stock tube. Couplers should be to BS EN 74-1 (Class B forged double couplers weigh about 1 kg). Base plates equal the number of standards. Add tie fittings, guardrail couplers (two per rail per standard) and toe board clips separately.
Common mistake
Counting doubles only and forgetting putlogs, swivels and joints, which can be half the fittings on a job.
Limits
Assumes ledgers fixed to standards with doubles, transoms on ledgers, braces on swivels. Excludes ties, guardrails, toe board clips and base plates. 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
- BS EN 74-1 Couplers, spigot pins and baseplates for use in falsework and scaffolds. Couplers for tubes
- Scaffolding Direct, Drop forged double coupler EN 74 Class B (1.011 kg)
- 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)
- NASC TG20:21 Good practice guidance for tube and fitting scaffolding (Operational Guide, Design Guide, User Guide and eGuide compliance sheets)
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.