Crane projects rarely fail on the crane. They fail on the 300 mm nobody measured — a sprinkler line, a light fitting, a duct running the length of the bay. By the time it shows up, the girder is fabricated and the erection team is on site. Space planning is the cheapest stage of a crane project and the one most often skipped. This guide covers every dimension worth checking before you order: vertical stack, mandatory clearances, floor coverage, structural capacity, service obstructions, and installation access.
Why Space Planning Comes Before Crane Selection
Capacity, girder type, and hoist configuration are all downstream of what your building physically allows. Choose the crane first and you spend the rest of the project forcing it to fit. Survey the space first and the specification narrows itself down to a short list of workable options — usually in a single afternoon.
The Vocabulary You Need First
Headroom, clearance, hook approach, dead zone
- Headroom — vertical space the crane occupies between the rail level and the lowest roof obstruction
- Clearance — the mandatory gaps between crane and structure, on all sides
- Hook approach — how close the hook can get to the ends and sides of the bay
- Dead zone — floor area inside the bay that the hook cannot reach
Use these four words precisely with your supplier. Half of all specification errors are vocabulary errors.
Vertical Space — The Full Stack From Floor to Roof
What sits between your load and the roof
Working upward from the floor: machines and fixtures, the load itself, lifting tackle, hook block, hoist body, trolley, girder depth, rail, and finally the clearance to the lowest roof element. Every one of these consumes vertical space, and the crane only gets what is left.
How to survey the lowest obstruction
Walk the full length of the bay with a laser measure and record the underside height of everything that projects downward. The truss bottom chord is almost never the winner. In most Indian factory sheds the lowest point is a light fitting, an exhaust duct, a cable tray, or a sprinkler branch — typically 300 to 900 mm below the truss.
Record the position of each obstruction as well as its height. Some can be moved cheaply; some are structural.
The low-headroom fixes when you fall short
If the stack does not fit, you have options before you touch the roof:
- Switch to a low-headroom or ultra-low-headroom hoist
- Move from double girder to single girder
- Change from top running to underslung
- Re-reeve the hoist to raise the top hook position
- Relocate the offending service instead of the crane
Most shortfalls of under 500 mm are solved by hoist selection alone.
Required Clearances You Cannot Negotiate
Above the crane
Leave a minimum of 75–100 mm between the highest point of the crane and the lowest roof element along the entire travel. Buildings deflect under wind and snow load, and a crane that just clears on a still day can strike on a bad one.
Beside the crane
Maintain at least 500 mm between the crane’s outermost point and any wall, column, or fixed structure along the runway — more where personnel access is possible. This is a crush-hazard clearance, not a convenience.
Below the crane
Keep 300–500 mm between the lowest point of the crane and the tallest fixed obstruction the crane travels over, with the hook at its highest. Also verify clearance to any mezzanine, walkway, or overhead conveyor within the bay.
Horizontal Space — Floor Coverage and Dead Zones
End approach and side approach
The hook cannot reach the extreme ends or sides of the bay, because the end carriages, trolley, and hoist occupy physical width. Typical figures: 700 mm to 1.2 m at each end, and 800 mm to 1.5 m at each side on a top running crane. Underslung cranes do considerably better on side approach.
Mapping the served area on your layout drawing
Take your factory layout, draw the runway lines, then draw the actual hook-reachable rectangle inside them. Now overlay your machines, storage racks, and loading points. This ten-minute exercise catches the problem that costs the most later: a machine or a truck bay sitting inside a dead zone.
Across a typical 20 m × 40 m bay, dead zones commonly account for 8–12% of the floor. That is not a defect. It is a planning input — put your consumables store, panel room, and staging there deliberately.
Parking and maintenance position
Decide now where the crane will sit when not in use and when being serviced. It should be clear of production, near a power isolation point, and reachable by a boom lift or from a walkway. Cranes parked over a machine turn every routine service into a production stoppage.
Structural Space — Columns, Corbels, Foundations
What the building has to carry
The crane imposes vertical wheel loads, lateral loads from acceleration and skewing, and longitudinal loads from braking. Sheds built for roof load alone frequently cannot take these. A structural engineer needs to check columns, corbels, bracing, base plates, and foundations — before the order, not after.
The wheel load conversation to have early
Ask your supplier for maximum wheel loads in writing at enquiry stage, and pass them to your structural consultant immediately. A supplier who can produce these within a day or two is doing real design work. One who defers the question until after the order is a risk you can identify for free.
Services and Obstructions Audit
The checklist of things that get in the way
- Light fittings and their hangers
- HVAC ducting and exhaust hoods
- Sprinkler and fire mains
- Cable trays and busbar runs
- Compressed air and process piping
- Roof ventilators and turbo fans
- Mezzanine edges and overhead walkways
- Existing monorails or jib cranes
- Overhead doors and their operating gear
- Dust extraction ducting
Relocation cost vs crane redesign cost
Compare both, honestly. Moving a lighting circuit or a cable tray is usually a weekend job and cheap. Changing the crane design to duck under a duct costs headroom for twenty years. Where a single service is the constraint, moving it is almost always the better economics.
Installation Access — The Step Everyone Forgets
Getting girders into the building
A 20 m girder arrives on a trailer and has to get inside. Check gate width, turning radius in the yard, door heights, and whether the girder can be brought in at all without removing cladding. Buyers have had to cut wall panels because nobody measured the approach road.
Crane access, floor loading, and shutdown planning
Erection needs a mobile crane inside or beside the building. Verify the floor can take its outrigger loads, plan the area to be cleared, and agree the production shutdown window in advance. Two to five days is typical for a standard installation, but that only holds if access is ready when the team arrives.
New Build vs Existing Shed
In a new build, tell your architect and structural engineer the crane parameters before the steel is designed. Adding crane provision at design stage costs a fraction of retrofitting it, and it lets you set rail level for the hook height you want rather than the one the roof allows.
In an existing shed, the sequence reverses: survey, structural assessment, then crane specification. Never order first and survey afterwards.
The Pre-Installation Survey Checklist
- Span at three points, rail centre to rail centre
- Bay length and full runway length
- Floor to underside of truss
- Floor to lowest obstruction, with each obstruction identified and located
- Existing rail top level, if applicable
- Column spacing, section sizes, and existing corbels
- Foundation drawings, if available
- Floor load capacity and floor condition
- Power supply point, available load, and distance to the runway
- Access route dimensions for delivery
- Photographs down the bay from both ends and up at the roof
FAQs
What is the minimum building height for an overhead crane? There is no universal figure — it depends on your lift height, load height, and tackle. As a rough guide, a small underslung crane can work in a 4.5 m building, while most useful top running installations want 6 m or more to the truss.
Can I install a crane if my roof is too low? Often yes, using a low-headroom hoist, an underslung configuration, or by relocating the services that form the actual constraint. A survey will tell you which of the three applies.
How much floor space does an overhead crane occupy? None, in a top running installation on existing columns. It uses vertical space and the small footprint of any new columns. This is its main advantage over gantry and forklift handling.
Who is responsible for the structural check? The buyer, working with a structural consultant, using wheel load data supplied by the crane manufacturer. A responsible manufacturer supplies the loads and flags concerns, but does not certify your building.
How long does the installation shutdown last? Two to five days for a standard crane, longer for heavy double girder units or where corbels and runway steel are being added. The area under the runway must be fully cleared for the duration.
Conclusion
Do the survey before the shortlist. Measure the lowest obstruction along the entire bay, map your dead zones on the layout drawing, and get wheel loads to your structural consultant. Those three actions prevent nearly every expensive surprise in a crane project.
Heben Crane runs a full pre-installation survey as standard — vertical stack, clearances, obstructions, structural capacity, and delivery access — and issues wheel loads and reactions in writing before anything is fabricated.
Book your Heben Crane site survey and get the space questions settled before you order.
