Layout and quantities
Number of bays and lifts for an independent scaffold
- where
- number of bays
- length of building face to scaffold (m)
- bay length (m)
- number of lifts
- height of the top working platform (m)
- lift height (m)
- standards (inner and outer lines)
- scaffold run length provided (m)
Explain this equation
Turns the length and height of a job into whole bays and lifts, and counts the standards for an independent scaffold two standards wide. It is the first step in a take-off.
Dividing the face length by the bay length and rounding up gives enough bays to cover it; the same for height and lifts. A run of n bays has n + 1 pairs of standards, one inner and one outer line, so 2(n_b + 1) standards. Because bays are rounded up, the run provided L_r is usually a little longer than the face.
Whole-number division rounded up, so the scaffold always covers the work.
Sense check: a 20 m face at 2.1 m bays needs 10 bays (21 m of scaffold) and 22 standards; 10 m high at 2 m lifts is 5 lifts.
Watch out: take bay length and lift height from the TG20 compliance sheet for the loading and boarding you need. This is for estimating only.
Turns the length and height of the job into whole bays and lifts, and counts the standards for a two-standard-wide independent scaffold.
Enter your values to see the result.
Good to know
Bay length and lift height come from the TG20:21 compliance sheet for the load class, board type and height. Lifts are commonly 2.0 m, so 10 m to the top platform is five lifts; add a guardrail lift above that. Each standard line needs a base plate and sole board, so the standard count is also the base plate count. Add bays for returns, corners and loading bays separately.
Common mistake
Dividing length by bay length and rounding down, leaving the end of the building without a bay, or forgetting the bay that runs past each end so the end of the work is reachable.
Limits
Straight runs only, constant bay length and lift height, two standards per frame. Corners, returns, bridges and loading bays are extra. 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)
- Squote, Independent tied scaffold (TG20:21 scope summary: bays up to 2.4 m, lifts up to 2.0 m, transoms at 1.2 m for 38 mm boards)
- HSE, Scaffolding: design, TG20 standard configurations, competence (CISRS) and inspection
- 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)
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.