Ringlock Scaffold Calculator (by component)

How to work it out

1. Bays = (length + width) x 2 divided by bay length, rounded up; the four sides are taken off as one straight run, so you do not have to work it out yourself. Standards = (bays + 1) x rows of standards, two rows for ordinary facade work. The plus one is because each end of the run needs a standard; it is not the number of rows.
2. The number of rows only changes when the platform has to be widened; ordinary facade scaffolding is two rows. Rows change exactly four quantities: standards x rows, longitudinal ledgers x rows, transoms x (rows - 1), and adjustable bases equal to the number of standards. Vertical braces and ties do not follow the row count. That is why three rows is 1.52 times two rows rather than 1.5, and four rows is 2.04 times rather than 2.0: the same 30 m by 14 m building at 24 m gives 27.86 t on two rows, 42.29 t on three and 56.72 t on four. Frame width = (rows - 1) x transom spacing, so three rows at 0.9 m transoms is a 1.8 m wide platform, not 0.9 m.
3. Make up each standard from stock lengths 3000/2500/2000/1500/1000/500 and leave no more than 300 mm to the adjustable base. Ringlock standards are fixed-length components: a 5 m leg is a 3000 plus a 2000, not one 5 m piece. A 3.0 m standard is a standard component listed in Table A.0.1, but depots stock different ranges, so tick only the lengths your depot actually holds — each of the six has its own switch; switching one off adds splices, taking a 24 m leg from seven to nine, and those splices must be staggered by 500 mm level by level.
4. Ledger levels = floor(height / lift) + 1. The plus one covers the bottom sweep and the top level; using ceil instead adds a whole level at non-integer lift counts, which on a 24 m scaffold at 1.5 m lifts is roughly 600 kg of extra steel.
5. Vertical braces turn on the 24 m line: at 24 m and above, one brace every three bays; below 24 m, every four bays. Columns = floor(bays / interval) + 1, minimum two, because the run has to start with a brace; braces = columns x lifts, each column continuous from base to top. Thirty bays at three-bay spacing is 11 columns, not 10, and that is the easiest line to undercount.
6. Total weight is the sum of quantity times the tabulated unit mass of each component type, then divided by the facade area to give steel per square metre for comparison against similar scaffolds.

Where it goes wrong

• Estimating ringlock as tube length times 2.82 kg/m treats a component system as loose tube. Ledger B-SG-1200 is nominally 1200 mm but actually 1152 mm and weighs 3.60 kg; a per-metre estimate gives 3.38 kg and understates by six per cent, and braces diverge further.
• Doubling the vertical braces as a matter of course. Clause 6.3.5 item 3 of JGJ/T 231-2021 requires them on the outer face only; bracing both faces is a project requirement, not the mandatory minimum.
• Reading the 24 m rule as above 24 m. The clause wording includes the boundary value, so 24.0 m itself takes three-bay spacing rather than waiting for 24.1 m; on a 30 m by 14 m building that is 15 brace columns and 240 braces against 20 columns and 320 braces, a shortfall of 80.
• Including head jacks in a facade scaffold. Head jacks belong on the top of shoring scaffolds, not on a facade where the top level carries a guardrail. Bases are 3.89 kg and head jacks 4.74 kg, so mixing them overstates the order.
• Using ceil for ledger levels where floor plus one is correct. The two agree only when the height is an exact multiple of the lift; otherwise the difference is a full level of ledgers, several hundred kilograms.
• Leaving all six length switches ticked when the depot does not stock them all. Order on eight 3000 mm lengths and find on site that nothing longer than 2.5 m was ever available, and both the splice count and the tonnage have to be redone. The same 30 m by 14 m building at 24 m is eight lengths and seven splices per leg at 27.86 t with all six lengths available, against ten lengths and nine splices at 27.98 t once the 3.0 m switch is set to out of stock — 240 extra splices over 120 standards. Each length has its own switch, so switch off exactly what is missing; asking only for the longest length is not enough, because a depot may stock 3.0 m but not 2.0 m.
• Scaling a two-row take-off by the number of rows. What actually scales is the transoms: two rows take one per node, three rows take two, four rows take three. On the same 30 m by 14 m building at 24 m, two rows is 27.86 t, so a 1.5 multiplier gives 41.8 t against an actual 42.29 t, and a 2.0 multiplier gives 55.7 t against 56.72 t — close enough on tonnage to look plausible, but the transom count is out by a full multiple. Note also that three and four rows fall outside the ordinary construction rules of section 6.3 of JGJ/T 231-2021, which is written throughout for two rows, so they need a specific method statement, and whether the middle rows or the inner face need braces is not addressed by the standard.

Material and cost

Ringlock is rented by the tonne-day or the square-metre-day, and rates vary widely between depots and with hire duration and whether erection labour is included, so no single rate is quoted here. When comparing quotes, pin down three things: charged by tonne or by area, whether delivery and collection are included, and the loss-and-damage rate per missing piece. Erection and dismantling labour is normally priced separately, by facade area or by tonne.

On site

• Adjustable bases are mandatory under every standard; do not substitute sole boards and sit the tube straight on the ground, and do not expect the screw thread to take up more than about 300 mm of level difference.
• Lift height should not exceed 2 m. The capacity advantage of ringlock comes from node stiffness, but standard stability is still governed by effective length, and beyond a 2 m lift the nodes cannot compensate for a slender standard.
• Never substitute coupler-and-tube scissors bracing for ringlock braces. Ringlock braces form a rigid connection through the rosette and wedge, whereas coupler bracing is friction dependent; inspectors routinely fail this substitution.
• A ground-bearing scaffold 24 m or higher is high-risk temporary works requiring a reviewed method statement, and 50 m or higher requires expert review. Both thresholds are inclusive.
• Take off by type and count before approaching the depot. Quoting a single tonnage invites the depot to make up the order from whatever lengths it has in stock, and the mismatch only surfaces on site, where a return trip costs programme time.
• Before ordering, tick the six length switches to match the depot's actual stock. Asking only for the longest standard is not enough: a depot may hold 3.0 m but not 2.0 m. Whether 3.0 m is available changes the order — a 30 m by 14 m building at 24 m is eight lengths and seven splices per leg at 27.86 t with all six ticked, against ten lengths and nine splices at 27.98 t with 3.0 m switched off. And something that bites harder than tonnage: splices must be staggered. This tool works out how one standard is made up; on site adjacent standards have to start with different lengths so that the splices of all 120 do not land on one level. The commentary to clause 5.2.1 of DB11/T 2100-2023 explains why — splices on a single level put some standards into tension and make them buckle under horizontal force.

Basis

• EN 12810-1:2003 Facade scaffolds made of prefabricated components — Product specifications
• EN 12810-2:2003 Facade scaffolds made of prefabricated components — Particular methods of structural design
• EN 12811-1:2003 Temporary works equipment — Scaffolds: performance requirements and general design
• OSHA 29 CFR 1926 Subpart L (scaffolds)