Documents for a site with a high pressure gas main easement
A gas main easement fixes your layout before you draw a plot. What the deed restricts, how the Health and Safety Executive consultation distance works, and the document set that answers it.
A high pressure gas main easement does not rule out building on the rest of the site, but it fixes your layout before you draw a single plot. Two separate systems govern gas main easement development. One is private: a deed registered against your title that bars structures, deep excavation and planting over the pipeline and gives the operator a permanent right of access. The other is public: the Health and Safety Executive is consulted on applications inside the consultation distance around a major accident hazard pipeline, and its advice shapes what the case officer feels able to recommend.
Confusing the two is the usual early mistake. Planning permission does not release you from the easement, and operator agreement does not satisfy the planning authority.
What the easement restricts
The deed sets the width of the strip, usually measured either side of the pipeline centreline, and lists the restricted operations. Expect a bar on permanent buildings, on raising or lowering ground levels beyond a stated tolerance, on deep-rooting trees, and on storing plant or materials over the main. The operator also keeps a right of entry for inspection, maintenance and emergency repair, which means access must stay physically available after your scheme is built.
Breaching the deed is a private law matter. The operator can seek an injunction whether or not you hold permission, and lenders and insurers will ask about it at the point of sale.
Get the pipeline located properly before you commit to a layout. Ask the operator for its plans, then confirm the position and depth on the ground with a utility survey and trial holes agreed in advance. Record plans are indicative. Pipelines laid decades ago are not always where the drawing says, and a two metre discrepancy can move a terrace. The same discipline applies to a site crossed by a public sewer, where the recorded line and the real line also diverge.
The consultation distance and the advice that follows
High pressure gas transmission pipelines are notified to the Health and Safety Executive under the Pipelines Safety Regulations 1996. Around each notified pipeline the Executive sets consultation distances, normally expressed as inner, middle and outer zones, and local planning authorities hold those zones as a constraint layer.
When an application falls inside a zone, the authority consults the Executive, which applies its published land use planning methodology. The method combines the zone the development sits in with a sensitivity level for the proposed use. The answer comes back as either no advice against the proposal or advice against it.
Advice against is not a refusal. The authority can still grant permission, and it is expected to notify the Executive before it does so against that advice. In practice very few officers will recommend approval over an advise-against response without something substantial on the other side of the balance, so treat the response as the gate it effectively is.
One point of vocabulary worth getting right. A hazardous substances consultation zone in the strict sense belongs to sites holding listed quantities of dangerous substances under the Planning (Hazardous Substances) Regulations 2015. A pipeline is not subject to hazardous substances consent, even though the consultation machinery around it feels much the same. If you describe your constraint using the wrong label in the application, expect the validation officer to query it.
Building proximity, population density and layout
Two filters run in parallel and they are not measuring the same thing.
The operator applies building proximity distances derived from engineering standards for high pressure steel transmission pipelines, worked out from diameter, wall thickness, operating pressure and design factor. That calculation is about the physical pipe. The Executive's filter is about people: how many, how concentrated, and how able they are to get themselves out of the way.
So sensitivity, not floorspace, drives the planning answer. Open storage, parking and sports pitches sit at the bottom. Ordinary housing sits in the middle. A nursery, school, care home or hospital sits at the top, and a care home can attract advice against at a distance where a row of houses would not. If your scheme includes a specialist residential element, place it as far from the main as the site allows and test that element first.
What usually works inside or beside the strip:
- estate roads and footpaths crossing at a controlled point agreed with the operator
- surface parking courts with shallow construction build-up
- amenity grassland, meadow planting and play equipment with shallow foundations
- bin and cycle stores only where the operator accepts a demountable structure
What usually does not work: attenuation basins, soakaways, substations, podium decks and anything needing piles. Drainage is the common casualty, because the easement strip is often the lowest part of the site and therefore exactly where an engineer wants to put storage. That conflict has the same shape as designing infiltration on a scheme in a Source Protection Zone: the hydraulically obvious answer is the one you cannot have.
Run the yield test early. A 40 metre corridor across a five hectare site can remove a whole development parcel, and that changes the affordable housing position and the viability case as well as the drawing.
Whether a diversion is realistic
Diversions happen regularly and the engineering is well understood. The difficulty is commercial and programme related.
The developer pays, and the cost is a function of pipeline diameter, length of new route, tie-in arrangements and the outage window the operator can offer. The operator will normally expect a paid feasibility study before it will say anything binding about route or price. Treat that study as the first item on the programme, not a later refinement.
Three things catch people out. The new route often crosses land you do not own, so you are back into easement negotiation with third parties and the planning programme now depends on a property transaction. The new corridor needs its own ecology, arboricultural and archaeological checks, which attach to the survey seasons. And gas transporters hold their own permitted development rights for pipeline works, so the diversion itself may not need a planning application while the enabling works on your site still do, which splits the consenting into two unsynchronised tracks.
If the numbers do not work, design around the main. A scheme that respects the corridor and gets determined is worth more than a diversion that stalls at feasibility.
Working near the main during construction
Nothing happens inside the easement without the operator's written consent, and that includes temporary works. The usual controls are a permit to work system, operator attendance for the first excavations, hand digging within a set distance of the pipe, physical protection where vehicles cross, axle load limits on crossing points, and a prohibition on stockpiling or on parking plant over the main.
Piling and vibration are the real sticking points. Any piled solution near the corridor needs a specific assessment agreed with the operator, and that assessment takes time you have probably not allowed for.
Your duties under the Construction (Design and Management) Regulations 2015 sit on top of all this. The pipeline must appear on construction drawings, the pre-construction information must identify it, and cable and pipe detection should precede every excavation. Put the controls in the construction management plan rather than leaving them to a condition, because an authority that can see the controls is far more likely to grant without a condition you then have to discharge before you can start.
The document set and who to approach
The pipeline constraint touches several documents rather than generating one of its own:
- Planning Statement, explaining the constraint, the layout response and the consultation position.
- Design and Access Statement, showing the strip as designed open space rather than left-over land.
- Utilities Assessment, recording the pipeline position, easement width, protection measures or diversion strategy.
- Construction Management Plan, covering crossings, exclusion zones and the permit to work regime.
- Drainage Strategy, showing attenuation and discharge clear of the pipeline corridor.
- Geotechnical Assessment, where piling or significant level change is proposed.
- EIA screening request, where the scheme crosses a Schedule 2 threshold on its own merits.
Browse all 66 report types by category to match that list to your scheme. On consultees, go to the pipeline operator first, before pre-application advice, because its answer on diversion or protection determines the layout you take to the authority. Then ask the authority to confirm the consultation zone in writing at pre-application stage. Approach the lead local flood authority on the drainage workaround, and the highway authority if a diversion involves road works.
An illustrative example. A promoter taking a five hectare greenfield site through outline permission finds a 600 millimetre main crossing the southern third. The feasibility study prices a diversion at a figure that removes the land value uplift, so the team instead places the spine road and two attenuation basins north of the corridor, puts surface parking and a kickabout area over the strip, and relocates the proposed children's nursery to the far boundary. The Executive returns no advice against. The scheme loses nine plots and keeps its programme. The figures here are illustrative only.
Enter your postcode on PlanScope to see which reports your site is likely to need before you commission anything.
This is general guidance, not legal advice; check the position with your local planning authority, the pipeline operator and a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.
Frequently asked questions
Can I build over a high pressure gas main easement if I get planning permission?
No. The easement is a private property right registered against your title, and planning permission does not override it. The operator can seek an injunction to stop works or require removal, regardless of any consent you hold. You need the operator's written agreement for anything inside the strip, including temporary works and changes to ground level.
How do I find out whether my site is inside a pipeline consultation distance?
Ask the local planning authority to confirm the constraint from its own mapping, and ask the pipeline operator in parallel. Both hold the information. Confirming it in writing at pre-application stage is worth the delay, because the zone you sit in determines which uses the Health and Safety Executive will advise against.
Is advice against a proposal from the Health and Safety Executive a refusal?
It is not. The authority remains the decision maker and can grant permission, but it is expected to notify the Executive before approving against that advice. In practice officers rarely recommend approval over an advise-against response, so plan on the basis that the response determines the outcome unless you can change the proposed use or its position.
Who pays for a gas main diversion on a development site?
The developer. Cost depends on pipeline diameter, the length and route of the replacement, tie-in works and the outage window the operator can offer. The operator will usually require a paid feasibility study before giving a route or price, so budget for that study and treat its output as a programme item rather than a detail.
Can a drainage attenuation basin go in the easement strip?
Normally not. Excavation for storage, soakaways or outfall structures conflicts with the restrictions in the deed and with the operator's cover requirements. Because the strip is often the lowest ground on the site, the drainage engineer has to design storage elsewhere and sometimes accept pumping, so raise it at concept stage rather than at technical design.
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.