Turbine Hall & Structures
The steel-framed building over the turbine-generator - designed from the crane downwards, because the hall exists to lift, open and maintain the machine inside it for the whole of the station's life.
Last updated 2026-08-25
Typical duration
Typically 6-12 months for the structures package, though the crane is the real clock - its design, manufacture and delivery are usually the longest lead in the phase.
What is Turbine Hall & Structures?
The turbine hall is the building everybody pictures when they think of a power station, and structurally it is one of the simplest things on the site: a braced steel frame, a clad envelope, an operating floor and a heavy overhead travelling crane running the length of it. Around it sits the rest of the structures package - the electrical and control buildings, the water treatment building, the workshop and stores, the pipe rack steel, and the platforms, ladders and stairs that let people reach the plant. None of that is difficult steelwork by the standards of a stadium or a tall building. What makes it a specialist job is that the building is not the point. The machine is the point, and the hall is there to serve it.
Start with the crane and the rest of the hall falls out of it. The crane duty is set by the heaviest single item the turbine supplier will ever need to lift off the machine - a rotor, a generator stator, an upper casing - and by where that item has to be set down afterwards. The supplier states the load and the hook coverage required, and that fixes the crane. The crane fixes the runway beams. The runway beams fix the column spacing, the column sections and the bracing. The clear height under the hook is set by how high the largest component has to rise to clear the machine and travel to the laydown bay, and that height sets the eaves. The footprint is the machine plus the laydown area beside it, because a rotor pulled out of a casing has to go somewhere. Design the shed first and choose the crane afterwards, and you get a building that cannot maintain the plant it was built for.
The hall also has to be built around the thing it covers, and the order is a genuine decision rather than a detail. On many jobs the frame goes up, the runway and crane are installed and proved early, and the hall crane is then used to install the turbine-generator itself - which puts the steelwork, the cladding and the crane proving squarely on the critical path for the mechanical phase. On others the machine is set with a crawler crane while the hall is still open, and the building is closed around it, which frees the steel programme but leaves a large hole in the gable until the last component is in. Either way the hall becomes the weather envelope that lets precision mechanical work happen indoors, on a clean dry floor. That is worth more than it sounds. A turbine is assembled to fine tolerances by people who need light, heat and somewhere to put things down, and no amount of temporary sheeting is a substitute for a finished roof.
Compare the methods at a glance
When and why is Turbine Hall & Structures used?
The structures phase overlaps the tail of the civils and runs into the front of the mechanical works, and its pacing item is almost always the crane. A heavy overhead travelling crane is a long-lead item designed for a specific building, so it is ordered early, and the runway steel cannot be finalised until the crane design is fixed. That chain - supplier data, crane design, runway, frame, foundations - runs backwards through the whole project, which is why the crane duty is one of the first numbers a power station design team settles on and one of the last things anyone should try to change. The hall is needed watertight and the crane proved before the turbine-generator arrives, because the machine is a precision assembly that should not be built in the weather and because on many schemes the crane is what installs it. Beyond the erection programme there is a thirty-year argument. This building will be opened up for major overhauls repeatedly over the station's life, and every one of those outages is time the plant is not earning. If the hall has a laydown bay big enough, a floor rated for what will be set on it, doors and routes that will pass a rotor out to a transporter, and hook coverage over the whole machine, then overhauls are quick. If it does not, every overhaul for the next thirty years costs extra days, and nothing can be done about it. The envelope carries a further obligation. A turbine hall is a significant noise source, and the acoustic performance of the cladding, the doors, the louvres and the ventilation openings is usually part of what the planning consent and the site's noise limits depend on - which makes the cladding specification a compliance item rather than a finish.
Types of Turbine Hall & Structures
Explore each method in depth - benefits, limitations, plant and quality control on its own page.
Enclosed steel-framed hall with an overhead travelling crane
The standard arrangement. A braced steel frame carries a heavy travelling crane on runway beams down each side, with a clad envelope, an operating floor and a laydown bay beside the machine. Gives full weather protection for erection and for every future overhaul, and gives the acoustic envelope the site's noise limits usually need. The most expensive option and, for a machine that will be opened repeatedly, normally the right one.
Semi-enclosed or weather-hood machine bay
A reduced structure - a hood, partial cladding or an open bay - served by a gantry or by mobile cranes brought in for outages. Cheaper and quicker to build, and common where the climate is kind or the machine is a simpler one. The trade is paid later: erection and maintenance happen in the weather, temporary protection is needed every time, and outages take longer.
Concrete or hybrid framed hall
Used where acoustic mass, fire separation, robustness or a particularly heavy crane makes concrete or a mixed frame the better answer. Heavier, slower to build and less tolerant of late change than steel, but it can solve a noise or separation problem that cladding alone cannot, and it suits sites with tight boundary constraints.
Ancillary and electrical buildings
The electrical, control, water treatment, workshop and store buildings. Individually ordinary structures, collectively a large slice of the structures package, and driven by completely different things - cable entry routes, equipment layouts, fire compartmentation, environmental control and the fact that the control building has to be finished early enough for the commissioning team to work from it.
Best suited for
- New build combined cycle and thermal stations where the machine will be overhauled repeatedly on site
- Any scheme where the hall crane is planned to install the turbine-generator as well as maintain it
- Sites with boundary noise limits, where the envelope is a compliance item rather than a finish
- Repowering projects placing a new machine inside or beside existing structures
- Projects needing a weathertight, clean working space to protect precision mechanical erection
Turbine Hall & Structures: step by step
- 1
Step 1: Fix the crane duty and let it size the building
Nothing on this package can be settled until the crane is. The turbine supplier states the heaviest component that will ever be lifted, where it has to be lifted from and where it has to be set down, and the maintenance strategy for the machine states how often. From that the crane capacity, span, hook coverage, lift height and approach dimensions are fixed, and from those the runway beam design, the column grid, the frame bracing and the eaves height all follow. The laydown bay is sized at the same time, because there is no point lifting a rotor out if there is nowhere to put it. This is also the moment to settle how the machine gets out of the building years from now - the door sizes, the external route and the hardstanding a transporter will stand on. Every one of those is cheap on a drawing and effectively impossible to change once the frame is up.
- 2
Step 2: Design, fabricate and trial-assemble the steelwork
The frame is modelled, connections are designed and the whole job is broken into fabrication pieces that can be transported and lifted. The break points are chosen around the crane and the route rather than around what looks tidy in the model. Fabrication happens in a shop, where welding is done under controlled conditions and inspected before anything leaves, and where the steel is prepared and coated to the protective system the environment demands - a power station is a corrosive place and the coating specification is not decorative. Complex assemblies, particularly the runway support arrangement and any heavily loaded connections, are frequently trial-assembled in the shop so that fit-up problems are found on a level floor rather than at height. Every piece is marked, and the erection sequence is planned so that pieces arrive in the order they are needed, because a laydown yard sorted by delivery date rather than lift sequence is a week of crane time thrown away.
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Step 3: Prove the foundations before the first column goes up
Before any steel arrives, the as-built survey of the bases is checked against the steelwork model. Bolt group positions, levels, orientations and projections are all compared, and deviations are resolved on paper by the designers, not on the day by a fitter with a gas axe. This step gets skipped surprisingly often and it is the single cheapest hour on the package. Base plates, packing, levelling arrangements and grout details are confirmed, and holding-down bolt threads are cleaned and checked after months under polythene. Where a base is genuinely out, the fix is engineered and recorded. Only then is the erection sequence confirmed and the crane mobilised. The point is simple: a crane standing idle while the engineers work out whether a column can be set is the most expensive way there is to discover a survey discrepancy that was sitting in a spreadsheet all along.
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Step 4: Erect the frame
Steel erection follows a planned sequence that keeps the structure stable at every stage, with temporary bracing, guys and props designed by the temporary works engineer rather than added by feel. Columns go up, are plumbed and packed, bracing goes in, and the frame is only released from temporary support when the permanent bracing is complete and signed off. On a turbine hall the erection is complicated by whatever is already inside it - foundations, plinths, sometimes plant already set - and by the crane having to work over and around all of it. Access for the erectors is planned as part of the sequence, using mobile platforms and designed access rather than climbing steel. Bolted connections are made up and checked to the procedure the designer specified, with the tightening method and the inspection regime coming from the design rather than from the erection gang. Fit-up problems are recorded and referred, never forced.
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Step 5: Runway beams, crane installation and proving
The runway is the part of the building the crane actually cares about. Runway beams are set, aligned and surveyed to the tolerances the crane supplier specifies, and those tolerances are tighter than anything else in the frame - a runway that wanders makes a crane skew, wear and eventually stop being reliable. Alignment is checked by survey along the full length, both rails together, and adjusted before the crane goes on. Rails, stops, conductor systems and access walkways follow. The crane itself is delivered in sections, assembled, and installed by the crane supplier working to their own method, then commissioned, function tested and load tested under their supervision with the results certified. Only after that certificate exists is the crane available to anyone else. From that point the hall crane is a construction asset as well as a maintenance one, and its availability starts appearing on the mechanical programme.
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Step 6: Close the envelope - roof, cladding and acoustics
Getting the building watertight is a programme milestone in its own right, because it releases the mechanical and electrical work inside. Roof sheeting, wall cladding, flashings, gutters and rainwater goods go on, along with rooflights, louvres, doors and the large openings the plant needed to get in. The acoustic performance of the whole envelope is checked against what the noise assessment assumed, and the weak points are the ones people forget - door seals, louvre attenuators, service penetrations and the ventilation openings that have to stay open for the building to work. Penetrations for pipes, cables and ducts are sealed and, where they cross fire compartments, firestopped by a specialist with the installations recorded. Where a gable or a roof bay has been left open so a component can still be brought in, the temporary closure is designed for wind and inspected, not just tied down.
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Step 7: Operating floor, plinths, stairs and permanent access
Inside the hall the operating floor, the mezzanines, the plinths, the stairs, the walkways and the handrails all go in, and their job is to make the machine reachable. Floor loadings are set by what will be laid on them during an outage, not by what walks on them day to day, and lay-down areas are marked and rated so that nobody has to guess. Access is designed around the maintenance strategy: routes to every valve, instrument and bearing that will be visited, headroom under the crane, and clearances that let a component be slung and swung without dismantling half the platework first. Floor finishes, drainage, bunding around anything holding oil, and lighting all follow. This is the part of the package that determines whether the station is a pleasure or a misery to work in for the next thirty years, and it is invariably the part under the most pressure at the end of the phase.
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Step 8: Ancillary buildings and handover to the mechanical team
The electrical, control, water treatment and workshop buildings are completed in parallel and to their own drivers. The control building in particular is needed early, because the commissioning team will work from it and the control system has to be installed, powered and environmentally controlled long before the plant it controls is finished. Buildings housing electrical equipment need their cable entries, floor voids, fire separation and environmental control completed before the equipment arrives, and once that equipment is in, the building is no longer a construction area in the way it was. Handover of the hall to the mechanical team is a formal step: the structure complete and signed off, the envelope watertight, the crane certified and available, the floor clean and rated, the permanent access in place, and any remaining openings identified with a date and an owner. What is handed over is not a building. It is a working space with a crane in it.
Plant & equipment
- Mobile and crawler cranes sized for the heaviest frame section and the longest reach, not the average lift
- Mobile elevating work platforms and designed access for erection at height
- Bolting equipment and tightening tools matched to the connection procedure the designer specified
- Total stations and precise levelling equipment for frame plumbing and runway alignment survey
- Cladding hoists, mast climbers and safety netting or air bags for envelope work
- Temporary bracing, guys, props and stability supports designed by the temporary works engineer
- Test loads and instrumentation for crane load testing, supplied and operated by the crane supplier
- Temporary lighting, heating and dehumidification to allow clean mechanical work inside the envelope
Quality control & testing
- As-built base survey reconciled against the steelwork model before any steel is delivered
- Shop inspection of fabrication, welding and protective coating before pieces leave the works
- Frame plumb, level and line surveyed as erection proceeds, not only at the end
- Runway beam alignment surveyed over the full length to the crane supplier's stated tolerances
- Bolted connections made up and inspected to the specified procedure, with records kept by connection type
- Crane commissioning, function testing and load testing certified by the crane supplier
- Envelope watertightness and acoustic performance checked against the design assumptions
- Firestopping at every compartment penetration installed by a specialist and recorded individually
Safety watchpoints
- Steel erection at height, with collective protection and designed access rather than climbing the frame
- Structural stability during erection, governed by the temporary works design and released in stages
- Heavy lifting over live foundations, installed plant and other trades working below
- Cladding work in wind, where sheets become sails and the limits need enforcing rather than judging
- Crane installation and load testing, with the area cleared and controlled by the crane supplier
- Fragile roof surfaces and openings left for plant access, which need designed covers and edge protection
- Simultaneous operations as mechanical and electrical trades move in under a frame still being completed
- Hot work inside a partially clad building, with fire watch and permit control
Common defects to hunt
- A crane specified from the building rather than from the machine, leaving hook coverage or capacity short
- Runway beams outside the crane supplier's alignment tolerance, causing skew, wear and unreliability
- A laydown bay too small or too lightly rated to take the components an overhaul produces
- Doors and routes that will not pass a major component out of the building to a transporter
- Acoustic performance lost at door seals, louvres and service penetrations rather than in the cladding itself
- Envelope leaks over installed electrical and mechanical plant, discovered during the first serious rain
- Firestopping missed or done badly at cable and pipe penetrations, then hidden by later work
- Permanent access omitted around valves and instruments, leaving scaffolding needed for routine tasks
How long does Turbine Hall & Structures take?
Typical duration: Typically 6-12 months for the structures package, though the crane is the real clock - its design, manufacture and delivery are usually the longest lead in the phase..