Scaffolding Near Overhead Lines: Safe Clearance Distances, DNO Notifications and Exclusion Zones

Summary

Overhead power lines are one of the most serious hazards in scaffolding operations and construction generally. Contact with a live overhead line can be instantly fatal — 11kV distribution lines, which look similar to domestic telephone cables, carry enough voltage to kill. Even approaching within the danger zone without actual contact can create a flashover arc.

The challenge with scaffolding is that tubes extend significantly above and to the side of the structure being accessed. A scaffold being erected near overhead lines can reach into the danger zone through the movement of individual tubes during assembly, even if the erected structure itself is clear of the lines.

HSE has produced specific guidance on working near overhead lines (GS6) and the Electricity at Work Regulations 1989 impose duties on anyone whose work could affect the safety of electrical systems. Importantly, the DNO (Distribution Network Operator — e.g. UK Power Networks, Northern Powergrid, Western Power Distribution) is both a critical resource and a duty partner — contacting them before work starts is not optional.

Key Facts

• Treat all lines as live — unless the DNO has confirmed the line is dead and isolated in writing
• Minimum safe working distance (11kV/33kV) — 3m horizontal and vertical from conductors (bare conductors or insulated cables; treat all as bare)
• Minimum safe working distance (132kV+) — 9m minimum [verify specific voltages with DNO/HSE GS6]
• DNO notification — contact the local DNO before any work commencing near overhead lines
• Exclusion zone — establish a physical exclusion zone (barrier or banning) around the area beneath and near overhead lines
• Voltage identification — check the number of wires (conductors) and insulator type; consult DNO if uncertain
• Underground cables — overhead cables may be diverted underground near buildings; confirm route with utilities search (e.g. LSBUD, utility searches)
• Diversions — DNO can arrange temporary diversion or de-energisation; plan lead times (weeks to months)
• GS6 — HSE guidance document "Avoiding Danger from Overhead Power Lines"; key reference
• Electricity at Work Regulations 1989 (SI 1989/635) — places duties on all persons creating risk to electrical systems
• Permit to work — formal permit may be required before working within specified distances
• Scaffold tube conductivity — metal scaffold tubes are excellent conductors; they carry electrical current from contact point to any grounded part of the structure or operative

Quick Reference Table: Overhead Line Voltage Levels and Typical UK Appearance

Exact clearance distances should be confirmed with the relevant DNO for each project — line characteristics vary.

Detailed Guidance

Identifying Overhead Lines Before Scaffold Erection

Before planning a scaffold, identify all overhead lines in the vicinity:

1. Visual survey — walk the site perimeter and look up. Note all overhead cables, including bundled insulated ABC cables (which can be mistaken for telephone lines), open conductors on wooden poles, and cables attached to buildings.
2. Utilities search — use LSBUD (Lines and Cables Searches) or contact individual utilities directly. Note that overhead line mapping is less comprehensive than underground cable databases.
3. Contact the DNO — the DNO for the area (check the Energy Networks Association for the relevant DNO) can advise on line voltage and ownership. National Grid is responsible for 132kV+ transmission lines; regional DNOs are responsible for 11kV and 33kV distribution.
4. Consider cable routes to buildings — service cables (typically 230V) run from poles to buildings; their route may pass directly over the work area.

Never assume a cable is dead, de-energised, or low-voltage because it looks old or unused. The only safe assumption is live.

Safe Working Distances

HSE GS6 sets out the principle that an exclusion zone should be established around overhead lines based on the minimum approach distance (MAD):

These distances apply to any part of the work activity — the operative, the scaffold tubes being handled, the scaffold structure — at any point during erection, use, and dismantling.

The exclusion zone should be:

• Physically marked on site (barrier tape, scaffold bays not erected, clear signage)
• Documented in the method statement and risk assessment
• Communicated to all operatives who will work in the vicinity

DNO Notification and Liaison

Contact the relevant DNO as early as possible — ideally at design/planning stage, not the day before erection. The DNO can:

• Confirm the voltage and ownership of any lines in the vicinity
• Advise on whether the work can be done safely with lines remaining energised
• Arrange temporary de-energisation (switching off the line during scaffold erection and critical works) — note this may require advance notice of weeks and a fee
• Arrange permanent or temporary diversion of the line underground or via an alternative route — note this typically requires months of planning
• Install temporary insulating sleeve guards on low-voltage overhead lines adjacent to the work (limited availability; check with DNO)

On larger projects, the DNO may require a formal permit to work (PTW) system before work within defined distances. The PTW is issued by the DNO and specifies conditions under which work can proceed.

The Scaffold Design Approach Near Overhead Lines

When designing a scaffold adjacent to overhead lines, the key question is: can the scaffold be designed so that no part of it (including tubes being handled during erection) can come within the minimum safe working distance?

Options:

1. Relocate the scaffold — if the design can be changed to move the scaffold away from the line, this is always preferred
2. Stop below the line — design the scaffold to terminate below the line height with adequate working room; may not be possible for tall buildings
3. Partial scaffold + MEWP — use scaffolding where it is clear of the line; use an insulated MEWP for the portions adjacent to the line
4. Temporary de-energisation — the DNO switches the line off during the period when scaffold tubes are being erected in the vicinity; requires formal DNO coordination
5. Physical barriers — in some low-voltage situations, temporary insulated covers on the cables; but this must be installed by the DNO, not the scaffolding contractor

For situations where scaffolding must pass close to overhead lines, a specific method statement and risk assessment covering the exact approach must be produced, reviewed by a competent person, and agreed with the DNO and principal contractor before work commences.

Specific Risks During Tube Handling

The highest risk moment is when individual tubes are being lifted and positioned during erection. A 6m scaffold tube can reach 6m horizontally as it is carried, and significantly higher if it is lifted or tilted. Key controls:

• No tube handling within the exclusion zone — even if the erected scaffold will be outside the MAD, tube handling must stay outside it
• Spotters — a dedicated operative watching the overhead line during all tube handling in the vicinity
• Wind — consider how wind can blow long tubes towards the line; suspend tube handling in high winds near overhead lines
• Route planning — plan the direction tubes are carried to ensure they cannot inadvertently enter the exclusion zone

Frequently Asked Questions

Who is responsible for identifying overhead line risk — the scaffolding contractor or the principal contractor?

Both. The scaffolding contractor has a duty under the Work at Height Regulations and Electricity at Work Regulations to assess and control risks during scaffold erection. The principal contractor has a duty under CDM 2015 to coordinate pre-construction information including utility locations. In practice, the principal contractor should provide overhead line information as part of the pre-construction information pack, and the scaffolding contractor should verify this independently during their pre-erection survey.

Can overhead lines be assumed to be insulated and therefore safe to touch?

No. Most distribution overhead lines in the UK are bare conductors. Some bundled aerial cable (ABC) used for low-voltage distribution appears insulated, but the insulation is weatherproofing, not electrical insulation. Never touch or work within the MAD of any overhead cable without confirmed insulation status from the DNO.

Can the DNO de-energise a line for us to scaffold safely?

Yes, but this is not a quick or free process. DNOs can arrange planned outages for scheduled work. The network must be managed carefully — de-energising a distribution line affects other customers. Typical lead times for a planned outage are 2–4 weeks minimum; for complex switching, longer. The cost varies; some DNOs include routine outages in standard network management, others charge. Contact the DNO early and in writing.

Are telecommunications cables (BT, Openreach) as dangerous as power cables?

Telecommunications cables (phone, broadband) carry very low voltages and are not a significant electrocution risk. However, damaging a telecoms cable can cause disruption to services and may result in liability. Treat them as a civil liability risk, not a safety risk, but still identify and avoid them in scaffold design.

Regulations & Standards

• Electricity at Work Regulations 1989 (SI 1989/635) — duty to prevent danger from electrical systems; applies to scaffold erection near overhead lines

• Work at Height Regulations 2005 (SI 2005/735) — risk assessment for work at height including overhead line proximity

• CDM Regulations 2015 — pre-construction information must include overhead line data

• HSE GS6 — Avoiding Danger from Overhead Power Lines; minimum approach distances and guidance

• Energy Networks Association — industry guidance on working near overhead lines

• BS 7671:2018+A2:2022 (IET Wiring Regulations) — relevant background on electrical safety near distribution infrastructure

• HSE GS6 — Avoiding Danger from Overhead Power Lines — key HSE guidance document

• Energy Networks Association — Safe Digging — overhead line safety for construction activities

• LSBUD — utilities search — overhead line mapping tool

• work at height regs 2005 — WAH Regulations risk assessment obligations

• scaffolding on public highway — highway scaffold considerations, often co-located with overhead lines

• scaffold inspection records — method statements and risk assessments as part of scaffold documentation

• mobile tower scaffold — tower scaffold height and overhead line risks