Local overview – How we will build it

Heathrow expansion would be one of the largest infrastructure projects in Europe. A project of this scale will inevitably mean some impacts for local communities during construction, but through mitigation Heathrow can control, reduce and manage many of those impacts.

We want to engage with those affected and commit to listening, understanding and caring.

Code of Construction Practice

A Code of Construction Practice (CoCP) will be put in place and a draft is available as part of this Airport Expansion Consultation. This will control, reduce and manage impacts during construction on people, businesses and the environment. It will also set out how we will engage with local communities and deal with complaints.

It will cover things like hours of work, site security and how we will deal with emergency incidents. It also describes how we will manage things like air quality, odour, noise, and water.

Heathrow will be required to comply with the CoCP and we will ensure our contractors adhere to it.

Construction activities will vary across the site, and will include development of roads, tunnels,terminals, rivers and other major infrastructure and the movement of large amounts of earthworks over an extended period.

Low impact techniques will reduce the amount of materials and waste, increase opportunities for off-site manufacturing (moving impacts away from the area) and reduce the time needed to build the project.

The expansion workforce will peak at approximately 14,000 during 2024-2025 and the code of conduct for workers will set out standards of behaviour including how they engage with local residents.

We will provide facilities and services on site for workers, dedicated bus services to transport them to and from site, dedicated temporary car parks and managed areas within the site for workers who bring their own caravans.

Construction mitigation

Our approach to construction will consider the effect on the community and we are developing solutions to mitigate this including:

  • We will ensure our sites are clean and well-managed.
  • Our construction sites will be secure and sympathetic to the local environment.
  • Before construction starts we’ll complete environmental surveys and measures to identify, relocate and protect wildlife and natural habitats.
  • We will bring some material and waste to and from the site by rail, using the Colnbrook rail terminal. This will provide direct access to site and reduce road traffic.
  • Construction vehicles used will be low emission.
  • The construction site will use grid electricity where possible to avoid mobile generators and reduce carbon emissions.
  • We will build utilities channels alongside the new roads to avoid the disruption of roads being dug up twice.
  • We will maintain right of way for pedestrians, cyclists and equestrians where safe to do so.
  • The new runway needs a lot of earth to level the area and prepare for construction. This will come from local borrow pits to reduce our carbon footprint and minimise truck journeys.

Managing landfill

Much of the area that will be developed was used as landfill in the past. We will need to dig out some of this and place it into new landfill created in borrow pits. These will be constructed to very high standards to protect the environment and residents.


Where excavated gravel, sand and clay cannot be immediately used on site it will be temporarily stockpiled. This can also be used as a noise, light and visual barrier between construction activities and the community.

Borrow pits

Land where gravel, sand and clay will be dug for use across the site. This means less need to bring materials to site via road. The borrow pits to the south of Harmondsworth will be used for new landfill. The one to the south of Poynings will be used for flood storage. The one east of Saxon Lake will be used for future terminal heating and cooling.

Working hours

Working hours will vary but we will mainly need to work 24 hours a day and seven days a week to open the runway as soon as possible. We are developing measures to reduce the impact of 24/7 working. These will focus on noise and lighting, and we will stagger shifts to reduce impacts on roads and transport.

We will also consider places and activities where 24/7 working may have unacceptable effects, and propose shorter hours or other restrictions. We will set out our proposals for each location where this applies in our application for development consent.

Further detail is available in the Construction Proposals document.

To runway opening in 2026

The map below shows what we expect to have built by the time the runway opens (shown indicatively as the end of 2026).

Early works

The first elements of expansion will include:

  • Burying power lines. This will allow us to remove the existing overhead power lines and pylons to the west of the new runway and ensure local services are not affected.
  • The Grundon recycling and waste facility in Colnbrook will be demolished.
  • We’ll also be carrying out archaeological and ecology studies in key areas including Harmondsworth, Colnbrook and Poyle to ensure we’re ready to start the main works from 2022.

Main works

As the main works begin, construction activity at this early stage will be across multiple sites and our initial focus will be to establish a secure boundary around these sites and implement measures to create a safe environment for the workforce and the community.

To create the space for expansion it is necessary to demolish some residential properties, existing buildings and community facilities during this phase.

We’re working with those impacted residents, communities and local authorities to identify appropriate mitigation measures. New river corridors will be created to channel the existing rivers and wildlife away from construction sites and the new runway. We’ll maintain the existing river corridors in their current condition until the new river corridors have been sufficiently established.


Earthworks is a key component of airfield expansion and will occur during most of this phase across the various sites. Works will include the digging of gravel, sand and clay from borrow pits for use across the site.

We also need to stabilise the existing landfills in order to build the runway.

The proposed borrow pits are located around Harmondsworth and Poynings. We will move in excess of 20 million cubic metres of earthworks. In the peak year it is expected approximately 8 million cubic metres will be moved.

Building the runway

Earthworks, construction of the new runway, taxiways and aprons will be complete.

Highways will be diverted with new sections of motorways and spur roads including the M25, A4, A3044, A3113 and surrounding local roads.
The realignment of the M25 will be constructed offline and will not close the existing road until the new one is ready.

As this phase nears completion, we’ll remove temporary construction materials and install new permanent signage and fences around the exterior of the site ready for opening.

2026 to 2030

Phase 2 consists of a number of smaller construction sites with their own respective secure boundaries. These sites are supported by construction support sites that will remain from Phase 1.

A major part of this phase is within the airport boundary. This includes the development of new terminal capacity (Terminals 5X and 2A) and other supporting infrastructure including new stands on the northern apron.

We will construct the Southern Road Tunnel connecting the south of the airport with Terminals 2 and 3.

Off airport, we’ll be realigning the A3113 including the Stanwell Moor junction. Once complete, this will improve traffic flow on the roads around Stanwell and Stanwell Moor.

During this phase, the construction support site north of Stanwell will begin to transform into the new southern parkway. The site will be developed in stages and will include colleague andpassenger car parking and a new transit system for connection to the airport.

New pedestrian access bridges and underpass links will connect the southern parkway with both Stanwell and Stanwell Moor to ensure the community can use the new transport links.

As works progress through this phase, the requirement for construction support sites around Colnbrook and Poyle will reduce and these will be returned to their original condition.

We’ll continue to use the railhead in Colnbrook to support our construction logistics operation and help reduce road traffic in the local community.

2030 to 2035

This phase will largely be focused on construction activity within the airport boundary as we continue to develop terminals and the northern apron of the airfield.

Some existing facilities will be demolished to allow the first phase of construction of the northern satellite terminal (see below).

Off airport, new road layouts will be developed around Sipson and Harlington as the northern parkway starts to be built close to the M4 junction. The northern parkway will include colleague and passenger car parking and will include a new transit system for connection to the airport.

These transit links will be available for passengers, local community and colleagues to use.

The southern parkway construction will complete creating new parking capacity. The new transit systems will be open providing access to the airport for passengers, the local community and colleagues.

We’ll continue to use the railhead terminal in Colnbrook to support our construction logistics operation and help reduce road traffic in the local community.

2035 to 2050

All terminals will be complete along with the northern apron and associated taxiways.

We will demolish Terminal 3 and expand Terminal 2. The northern parkway will complete providing parking and direct terminal connections around Harlington and Sipson for passengers, the local community and colleagues.

We’ll continue to use the rail terminal in Colnbrook to support our airport logistics requirements and help reduce road traffic in the local community as we transition from construction through to airport operations.