Construction within operational production facilities. What you need to know

Expanding a factory is one challenge. Expanding a factory while it keeps producing 24/7 is a different problem entirely. Most construction guidance assumes a clean site, predictable access, and the freedom to stop and restart work as design decisions evolve. None of that applies when there are people on shift behind the wall you’re working on, raw materials moving through corridors you need to cross, and a production line whose downtime is measured in tens of thousands per hour.

This guide is for plant managers, operations directors, and development leads weighing an expansion of an existing facility. It covers what’s different about building in a live industrial environment, where projects of this kind typically go wrong, and the questions worth asking before you commit.

Key takeaways

Brownfield construction in an operating facility is fundamentally a coordination problem, not just a construction problem.
The biggest risks are usually operational, not structural: production disruption, material flow, safety overlap between workers and operators.
Phased sequencing is the core delivery tool – but it only works when planned around the operating reality of the plant, not the convenience of the build.
Existing structures often come with incomplete documentation. Surveys and ground investigations before design are not optional.
The right delivery partner runs construction around your operations, not the other way around.

What makes construction in operational facilities different?

When you build on a greenfield site, the constraints are mostly physical: ground conditions, weather, supply chain. When you build inside or around an operating plant, you inherit a second layer of constraints – operational:

People are working in the same building you’re constructing in
Maintenance equipment must keep functioning
Raw materials, recycled materials, and finished goods still need to flow
Statutory inspections, audits, and certifications can’t pause for your project
Some equipment is sensitive to dust, vibration, or temperature changes

Every one of these constraints adds decisions to be made before the first wall comes down. Get them wrong, and your construction project becomes the reason production missed quarterly numbers.

Where these projects typically go wrong

Across live-site expansion projects, the same patterns emerge. They’re worth naming because most of them are avoidable with the right planning.

1) Treating it as a construction project, not an operations project

The technical scope of the build may be straightforward – a new bay, an extension, a structural reinforcement. The hard part is sequencing it so production isn’t disrupted. Teams that focus only on the build inevitably collide with the operational reality.

2) Underestimating what you don’t know about your own site

Many operating facilities have been extended, modified, or repurposed over decades. As-built documentation is often incomplete or inaccurate. Foundations have been added, services rerouted, structural elements modified – and not all of it is recorded.

On one of our glass plant expansion projects in Bucharest, the existing building dated from the 1960s and only fragmentary legacy drawings were available. Extensive surveys had to be run before design decisions could be made with confidence. If design begins before this verification, the problems surface on site, after commitment. That’s the most expensive moment to discover them.

3) Single-front construction in a multi-front problem

Some live-site projects can’t be delivered linearly. The plant footprint, production zones, and access routes may require multiple work fronts running in parallel, each with their own logistics and safety setup. Trying to compress this into a single sequence often extends the programme rather than shortening it.

4) Underplanning material flow during construction

Production needs materials in and goods out, every day, regardless of whether your contractor is working that day. If the construction project blocks or compromises those flows – even partially – operations pay the cost. Material flow continuity has to be designed in from the start, not improvised once works begin.

5) Ignoring the maintenance team

The same equipment your contractor is working near needs to be serviced, inspected, and (occasionally) repaired during the construction period. If maintenance access isn’t planned alongside construction zones, you create conflicts that surface at the worst possible time.

The technical challenges that recur in industrial brownfield work

Some constraints come up so often in live-site expansion that they’re worth knowing about before you start.

High groundwater and difficult soil conditions

Many industrial sites sit on ground that wasn’t selected for ideal building conditions – it was selected for logistics, utilities, or historical reasons. High groundwater and sandy soil are common, particularly where the original facility was built decades ago. On the Bucharest glass plant expansion, adapted foundations with injected piles were needed, alongside a high-capacity pumping system handling over 135 m³ per hour. Water-table management during excavation isn’t an unusual edge case; on many sites, it’s the default condition.

Building around or under existing foundations

Expansions rarely happen on empty ground next to the existing plant. They often happen against existing structures, over existing foundations, or under existing services. On the same Bucharest project, parts of the new structure had to be built below the level of existing massive foundations, without compromising stability. New structural elements must be introduced without compromising what’s already there – and what’s already there may not be exactly what the original drawings show.

Legacy buildings with incomplete documentation

When a building has been operating for 30, 40, or 50 years, the documentation has usually been touched by multiple owners, multiple contractors, and multiple regulatory frameworks. Some changes were drawn up. Some were noted in margins. Some were never recorded at all.

Before design decisions can be made with confidence, surveys and expert assessments are usually needed. Skipping this step is a false economy: the costs surface later, as changes during construction.

What good looks like: how live-site expansion should be planned

A live-site expansion is planned backwards from one question: how do we keep production running while we build?

That changes how every phase is structured.

Phased sequencing built around production

Rather than designing the construction sequence and asking production to accommodate it, the sequence is designed around the plant’s operating reality – shift patterns, maintenance windows, peak production periods, audit schedules. Construction phases are chosen to minimise the operational footprint of each stage.

Site zoning and protective measures

Construction zones are physically and operationally separated from production zones, with controlled access, dust and noise mitigation, and clear safety routines for any overlap. The point is not just compliance – it’s making sure your operators and your contractors can do their work without interfering with each other’s.

Coordinated material flows

Logistics during construction need to be planned for both sides: how raw materials, recycled materials, and finished goods continue to move; and how construction materials and waste move in and out without crossing production routes. On larger projects, this requires explicit traffic planning.

Stability-first adaptation

When new structures need to integrate with existing ones, design choices are made to introduce new requirements without compromising the stability or functionality of what’s already there. This sounds obvious; in practice, it’s often where compromises slip in.

What stays with you, and where the right partner makes the difference

A construction project in an operating facility transfers a lot of responsibility to your delivery partner – but not all of it. What stays with you, and what the right partner should handle before it becomes your problem:

Knowing your operating constraints. Only your team knows what really can’t stop, what shift patterns look like, what audits are coming. That knowledge has to feed the planning phase explicitly.
The condition of existing structures and ground. This stays with you unless your delivery partner investigates it upfront – through site surveys, ground investigations, and assessment of existing structures – before designs are finalised.
Material flow continuity. Your partner should plan around your logistics, not ask you to plan around theirs.
Communication with your team. Daily handovers between construction and operations, weekly progress visibility, photo and video documentation from site – these aren’t extras. They’re what keeps a live-site project from drifting into operational risk.

How GFS approaches construction in operational facilities

This is the kind of work GFS has built its approach around. We’ve delivered live-site expansions across glass manufacturing (Bucharest, Sofia), rail and transportation manufacturing, and other industrial sectors – across project sizes from 15,000 m² to 65,000 m². A few things that are different about how we deliver:

Planning starts from your operating reality. Before design decisions are made, we map your shift patterns, peak production windows, maintenance schedules, and material flows. The construction programme is built around those constraints – not the other way around.

Surveys before commitment. For brownfield projects, we run extensive site and ground investigations, and – where existing documentation is incomplete – expert assessments of existing structures. Foundations, services, and structural elements are verified before designs are committed to.

Phased sequencing and multiple work fronts. Where the plant footprint requires it, we coordinate multiple work fronts in parallel, with site zoning that physically separates construction zones from production zones. Each phase is planned to minimise the operational footprint.

Stability-first design adaptation. When new structures must integrate with existing ones, our design choices preserve the stability and functionality of what’s already in place – because for you, the existing facility is not a backdrop, it’s the business.

Material flow continuity. Logistics during construction are planned for both sides – your production flows and our construction flows – so raw materials, recycled materials, and finished goods continue to move throughout the project.

Visible progress, every week. Weekly reporting as standard, daily on fast-moving phases, with photo and video documentation from site. Your team sees what’s happening without chasing for updates – and any drift gets caught early, when it’s still cheap to correct.

One accountable Project Manager, end to end. From the first site survey through to start of operations in the expanded facility, you work with one dedicated person responsible for coordination across planning, design, build, and the handover that follows.

Beyond handover. Once construction is complete, we prepare maintenance programmes and training for your team – because for you, the project ends when the new space runs reliably, not when the contractor leaves site.

Case in point: live-site reconstruction at 65,000 m² (Sofia, Bulgaria)

“We have reconstructed pretty much all the plant, after demolishing 35 buildings, maintaining part of some, all of this without stopping the production 24/7.”

What the project involved: A complex rebuild of a glass manufacturing plant with production facilities, furnace, and warehouses – delivered while production continued without interruption.

Constraints we worked around:

24/7 production throughout the works
High groundwater requiring continuous pumping across the construction period
Multiple production and warehouse areas spread across the plant footprint, requiring multiple work fronts in parallel
Old installations with incomplete as-built documentation – extensive surveys were needed before design
Coordination with local authorities to realign plant borders and update maps to match real conditions on site

What that meant in practice: 35 buildings demolished and reconstructed in phases, production maintained throughout, and the redesign aligned to the facility’s actual operational needs rather than the legacy drawings.

This is the level of operational complexity that “construction in an operating facility” can mean. Smaller expansions are easier – but the principles are the same.

A practical checklist: questions to ask before you commit

Use this as a planning filter or a tender interview guide.

What can’t stop during construction – and what’s the cost if it does?
What shift patterns, audits, and peak periods need to be designed around?
How complete is our as-built documentation? What needs to be verified before design?
What ground conditions are likely, and what investigations are needed before the price is locked?
What’s the plan for material flows during construction – ours and theirs?
How will construction zones be separated from production zones?
Will single-front or multiple-front delivery be needed, and why?
How will progress be reported – and how often will we see what’s happening on site?
What does handover include for our operations and maintenance team?
Who has delivered a live-site expansion of comparable scale – and can we see how it’s running now?

This guide is general orientation for plant managers and operations leaders evaluating an expansion. Specific construction and operational planning should be developed with qualified partners who can assess your site directly.

A low-pressure next step

If you’re planning an expansion of an operating facility, we’re glad to talk through what’s likely to be the hardest part for your site specifically – and how we’d approach planning, surveys, and phasing to keep production running while we build.