Evidence for a site with overhead power lines across it
The easement strip, the statutory clearance and the crane exclusion zone are three different restrictions. Establish all three before drawing the layout.
An overhead electricity line across a site reduces the developable area before any planning policy is applied. The easement strip cannot be built on, the statutory ground clearance limits what can pass beneath, and the construction exclusion zone around the conductors is wider than the easement. On overhead power lines development the sequence that works is: establish the voltage and the owner, obtain the easement or wayleave terms, survey the conductor positions and sag, then draw the layout. Doing it in the other order produces a scheme that has to be redrawn after the first consultation response.
The constraint is also one of the few that is non-negotiable in planning terms. The network operator's requirements are not a material consideration to be weighed; they are a physical limit.
Why the line comes before policy
A planning officer can be persuaded about density, massing or parking. Nobody is going to be persuaded that a house can sit under a 132 kilovolt line.
Three separate things restrict the land.
The easement or wayleave, which is a private right held by the network owner and typically defines a strip either side of the line within which building, excavation and planting are controlled or prohibited.
Statutory clearance, set by the Electricity Safety, Quality and Continuity Regulations 2002, which require minimum heights above ground and above buildings by voltage. Those clearances are measured to the conductor at maximum sag and maximum operating temperature, not to the conductor on a cold day.
Construction safety distances, which during the build are wider than either. Health and Safety Executive guidance GS6 sets out exclusion zones and barrier distances for working near overhead lines, with greater distances for higher voltage lines on steel towers than for lower voltage lines on wood poles. Confirm the distances with the owner for the specific line rather than working from a general figure.
Easements, wayleaves and who holds them
Establish ownership first, because the answer determines who you negotiate with and how long it takes.
- Transmission lines at the highest voltages are held by the transmission owner for the region.
- Distribution lines are held by the distribution network operator for the licence area.
- Private lines serving a single site may be owned by the landowner or an industrial occupier.
Then establish the legal basis. A registered easement appears on the title and binds successors. A wayleave is a terminable agreement, often annual, and may be a necessary wayleave granted under the Electricity Act 1989. The difference matters, because a wayleave can sometimes be terminated and the line moved, while a registered easement normally cannot be dealt with except by agreement.
Read the terms, not the summary. Easement wording varies, and the restriction may cover excavation depth, tree planting, the storage of materials, and access for maintenance as well as building. The maintenance access right is the one applicants forget, and it can require a permanent vehicular route to each tower or pole across a finished layout.
The parallel is a site crossed by drainage apparatus, where the undertaker's rights constrain the layout in the same way. The approach set out for a site crossed by a public sewer applies here too: find the apparatus, find the right, then design.
Clearance and exclusion zones in practice
| Item | What to establish |
|---|---|
| Voltage and circuit identity | From the owner, in writing, with the line reference |
| Conductor positions | Topographic survey of each pole or tower, with conductor positions |
| Sag and swing | Maximum sag and conductor swing envelope, from the owner |
| Statutory clearance | Minimum height above ground and above any building, by voltage |
| Easement width | From the deed, not from an assumed figure |
| Construction exclusion zone | From the owner, with reference to GS6 |
| Maintenance access | Route, width and surfacing required |
The survey has to be done by a surveyor and tied to a datum. Conductor heights scaled off aerial imagery are not usable, and a scheme designed on them will fail when the owner reviews the layout.
Note also that the swing envelope moves. Conductors move laterally in wind, so the restricted zone is wider than the plan position of the cable.
Diversion and undergrounding
Both are available and both are expensive and slow. Treat them as programme items from day one.
The process is to apply to the owner for a budget estimate, then a firm quotation, then a connection or diversion agreement. Lead times are long, commonly more than a year for a distribution line and substantially longer for a transmission circuit, because the works require outages, consents and sometimes land rights from third parties.
Undergrounding brings its own constraints. The buried cable needs its own easement, usually with a restricted strip that cannot be built on or planted, so the developable area is improved rather than freed. Excavation along the route can also trigger archaeological requirements, and where the site lies in a sensitive area the position for a scheme in an Archaeological Priority Area should be checked before the route is fixed.
Do not budget a diversion on the basis of a verbal indication. Get the budget estimate in writing and allow contingency, because the quotation frequently differs from the estimate once the detailed design is done.
Construction: cranes, scaffold and plant
The build phase is where incidents happen, and planning conditions increasingly reflect that.
Tower crane oversail of a live line is normally prohibited outright, which affects crane position, jib length and sometimes the whole construction method. Mobile crane and excavator operations near the line need goalposts, barriers and a banksman, and the exclusion zone has to be marked on the site layout. Scaffolding, tipper bodies and concrete pump booms all reach higher than people expect.
Your construction management plan should show the line, the exclusion zone, the crane positions and radii, the material storage areas kept clear of the zone, and the permit to work arrangements agreed with the owner. Expect the council to condition it and expect the owner to want to see it.
An illustrative example. A 1.8 hectare site is crossed diagonally by a distribution line on wood poles with a registered easement 15 metres wide. The developable area after the easement is removed is 1.5 hectares, but the crane exclusion zone during construction would prevent any crane serving the eastern plots. The scheme is resolved by placing the access road and attenuation basin within the easement, keeping all dwellings outside it, and programming the eastern plots for traditional construction with no crane. No diversion is needed, and the layout is designed around the constraint rather than against it.
Showing it on the submitted drawings
Make the constraint visible, because a council that cannot see it assumes it has been ignored.
- Mark the line, poles or towers, the easement strip and the exclusion zone on the site location plan and the proposed layout.
- Provide a constraints plan at the same scale as the layout, with the easement dimensioned.
- Include a section through the line showing clearance to any structure beneath or adjacent.
- Show the maintenance access route and its surfacing.
- Include the owner's written confirmation of the line details and, where obtained, their comments on the layout.
- Address the position in the planning statement, including any diversion programme.
Electromagnetic fields come up in objections. The position in national policy is that the separate regulatory regime for exposure is assumed to operate effectively, so the planning application is not the forum for it. Say that plainly, reference the regime, and avoid being drawn into a technical argument the planning system does not decide.
You can browse the report types to check which technical assessments the rest of the site constraints will need, and enter your postcode on PlanScope to see what a site with this profile is likely to trigger.
This is general guidance, not legal advice; check the position with your local planning authority, the network owner or a qualified professional before relying on it. PlanScope produces AI-assisted draft reports for planning applications, and reports should be reviewed before submission. For specialist technical reports, qualified professional input may be required. PlanScope does not guarantee planning approval.
Frequently asked questions
Can you build under an overhead power line?
Generally not within the easement or wayleave strip, which usually prohibits building outright. Statutory clearances under the Electricity Safety, Quality and Continuity Regulations 2002 also set minimum heights above ground and above buildings by voltage, measured to the conductor at maximum sag. Confirm the restrictions with the network owner in writing.
What is the difference between an easement and a wayleave?
An easement is a property right registered against the title that binds successors in title. A wayleave is a terminable agreement, often annual, and may be a necessary wayleave granted under the Electricity Act 1989. A wayleave can sometimes be terminated and the line moved, while a registered easement normally requires agreement to deal with.
How wide is the construction exclusion zone?
Wider than the easement, and it varies with voltage and support type. Health and Safety Executive guidance GS6 sets out barrier distances, with larger distances for higher voltage lines on steel towers than for lower voltage lines on wood poles. Obtain the figures for the specific line from the owner rather than using a general number.
How long does a diversion or undergrounding take?
Long enough to be a programme item from the outset. Apply for a budget estimate, then a firm quotation, then a diversion agreement. Lead times commonly exceed a year for a distribution line and are substantially longer for a transmission circuit, because outages, consents and sometimes third party land rights are involved.
Do electromagnetic fields need to be assessed in the application?
National policy proceeds on the basis that the separate regulatory regime for exposure operates effectively, so the planning application is not the forum for assessing it. State that position, reference the regime, and avoid being drawn into a technical argument that the planning system does not determine.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.