High-Rise Rising Mains & Busduct SWMS

High-rise rising mains and busduct installation is high risk construction work in New South Wales because it is carried out on or near energised electrical installations — including risers that are energised in stages while installation continues above — involves a risk of a person falling more than 2 metres in riser shafts and at penetrations, and is carried out in areas with movement of powered mobile plant during hoisting. Section 291 of the Work Health and Safety Regulation 2025 (NSW) captures all three categories, and a safe work method statement is required under section 299. SafeWork NSW is the regulator. AS/NZS 3000 governs the installation and AS/NZS 61439 the busbar trunking system.

The hazard that defines this work arrives partway through the job, and it is the project programme that delivers it. On a high-rise the riser is energised in stages so that fit-out can proceed on the lower floors while installation continues above. From that day forward the crew works on a conductor system that is **live below and dead above, with the boundary moving as the job advances**. A tap-off box on level 3 is on an energised busbar while the crew joints sections on level 12 of the same duct. The most dangerous assumption on this job is yesterday's: the section that was dead last week is not dead this week, and the only truth is the permit, the proving and today's energisation state confirmed with the principal — never the crew's memory of it.

The second cluster is the shaft itself. A riser is a vertical void running the height of the building — a fall path down and a drop path onto every trade below — and busduct sections are heavy, rigid and hoisted inside it. Every penetration the duct passes through is a breach in the building's fire compartmentation until it is reinstated, and an unsealed riser is a chimney for as many nights as the seal is left for tomorrow. The third mechanism is quieter: a long busduct run holds a capacitive charge after insulation resistance testing, and the tester's needle returning to zero reads the instrument, not the duct.

Hazards identified

14 hazards covered, sorted by priority.

Control measures

Hierarchy-of-controls order: elimination → substitution → isolation → engineering → administrative → PPE.

1. 1**Treat the entire duct as energised until today's energisation state is confirmed with the principal**, isolate the section at the point of work under permit, and prove it dead at the point of work every day — the boundary between live and dead moves with the programme, and the crew's memory of last week is the most dangerous document on site.
2. 2Exclude every person from the shaft void and from floor openings below for the whole hoist, plan the lift with the manufacturer's lifting points and rated gear to AS 4991 on a hoisting beam of verified capacity, and restrain sections against swing within the shaft.
3. 3Identify every possible source into the duct before any isolation is accepted — standby generator, UPS, solar, temporary builder's supply — verify isolation at each, and prove dead with an instrument proved on a known source before and after.
4. 4Obtain an arc flash risk assessment establishing incident energy and approach boundaries at the actual equipment, verify upstream protection, and install tap-off units on dead sections rather than plugging onto live busbar wherever the programme allows.
5. 5Complete all jointing, tap-off installation and verification on proven-dead sections under Part 4.7 Div 4 ss.154 & 157, with a competent person and a second person present who can isolate and perform rescue for any energised task.
6. 6Provide edge protection or rated fixed covers at every riser opening, a designed working platform for work within the shaft, and rated anchor points with a rescue plan before any harness use — an open hatch in a floor is the site's most reliable fall.
7. 7Close the shaft below the work with rated covers or catch decks before overhead work begins, use tool lanyards over the void, contain materials in lidded crates, and exclude the shaft base and openings below during overhead work.
8. 8**Discharge the run through the tester's discharge function after every insulation resistance test and prove the duct at zero before any terminal is touched** — a long run stores enough charge from the test voltage to injure, and the instrument's needle at zero reads the instrument, not the duct.
9. 9Make every joint to the manufacturer's method — torque figures, contact preparation, hardware and sequence — with calibrated tools and joints marked as torqued, and thermographically survey the riser under load at staged energisation.
10. 10Reinstate each penetration with the tested fire-stopping system for a busduct penetration as the duct advances, track reinstatement on a floor-by-floor register, and provide temporary fire-rated sealing where a penetration must stand open overnight.
11. 11Programme shaft work and outages with the principal so occupied floors are not exposed, lock riser cupboards on occupied floors against public access, and notify any outage to an occupied floor in advance.
12. 12Use cast-in or existing penetrations where the design allows, apply on-tool extraction or wet methods for all drilling and coring, contain dust so it does not travel the shaft, and clean by vacuum rather than sweeping.
13. 13Assess noise exposure against the exposure standard, use cast-in fixings and lower-noise methods where available, and select hearing protection to the measured level to AS/NZS 1270.
14. 14Hoist sections mechanically and position with the hoist rather than muscling into line, land sections on temporary supports at the working level, and never manually support a section while fixings are made.

Applicable Codes of Practice

High-Risk Construction Work triggered

Worked example

An electrician returns from a week off to continue tap-off installation on a residential tower's rising main. He worked level 8 before the break and is picking up where he left off. He knows the duct is dead — he proved it himself the week before, at the switchboard, and nothing about the job has changed. While he was away, levels 1 to 6 were energised for fit-out. The riser he is standing at is one continuous duct. He opens a tap-off position and is electrocuted by a busbar that had been dead for the entire duration of his knowledge of it. The investigation finds no failure of any control that was applied — the failure is that no control existed for the passage of time. The isolation he relied on was real and had been correctly performed; it was simply a week old, and in that week the programme had moved the boundary six floors up. Nobody told him because nobody had a process that required telling him: the energisation was a milestone on the builder's programme, not an entry in a document the electrical crew read each morning. The contractor's SWMS described isolation and proving accurately. SafeWork NSW's position was that it described them as one-off acts, and that on a staged riser the energisation state is a **daily variable** — so the SWMS must require it to be confirmed with the principal each day and proved at the point of work, not at the board and not last week. This SWMS names the moving boundary as the defining hazard, requires today's state confirmed before work, requires proving at the point of work rather than at the switchboard, and requires the boundary physically signed and barriered on every affected floor.

Related legislation

• Work Health and Safety Act 2011 (NSW) — primary duty of care (s19), consultation (s47), notifiable incidents (ss35–38), industrial manslaughter (s26A)
• Work Health and Safety Regulation 2025 (NSW) — HRCW (s291), SWMS content and requirement (s299), SWMS review (s302)
• Work Health and Safety Regulation 2025 (NSW) — Part 4.7 Division 4, sections 154 and 157 — prohibition on energised electrical work
• Work Health and Safety Regulation 2025 (NSW) — Part 4.4 — management of the risk of falls
• Environmental Planning and Assessment Act 1979 (NSW) and the National Construction Code — fire compartmentation and penetration reinstatement obligations

Frequently asked questions