Guide to loss prevention
© Getty Images/Aleksandar Reba

Tower cranes collapsing on construction sites

A guide to loss prevention

    alt txt



    In recent years, a number of tower cranes have collapsed on construction sites causing serious accidents involving personal injury, significant property damage and business interruption.

    The hazards which increase the risk  of a collapse event are numerous  and can include poorly designed  foundations, operating in high winds  (including impaired free-slewing  arrangements), lack of maintenance,    inexperienced crane operators and  supervisors, and underrated crane  capacity. Many incidents are as  a result of documented safety  procedures not being followed.

    This document aims to provide  a guide to the prevention of collapse  events involving tower cranes.  Whilst there are different types  of tower crane, and the specific  operating instructions for a  particular crane should be referred  to, many of the loss prevention  principles are common.

    A list of common terms and definitions  is located at the end of this document.

    Further industry best practice  guidance is included at the end of  this document, and the reader is  strongly recommended to refer to  BS 7121, CIRIA guide C703 and CPA  guidance information.

    Key components in preventing the collapse of tower cranes include the following.

    Hired Crane (hired and managed) Contract Lift (fully contracted)
    The employing organisation must: The employing organisation should specify:
    - Carry out all work in accordance with BS7121 - Supply the Appointed Person - Plan the lift and operate a safe system of work - Ensure that the crane hired is of a suitable type, capacity and configuration - Check the credentials of the crane hire company and certification supplied - That all work is to be undertaken in accordance with BS7121 - That the crane owner/contractor is to supply appropriately maintained and certified equipment and Competent Persons - What information and/or services will be provided to the contractor by the employing organisation
    The crane owner has a duty to: The crane owner/contractor is responsible for:
    - Provide the loads imposed by the crane to assist with the design of a suitable support - Provide a crane that is properly erected, maintained, tested and certified - Provide a competent driver (where required) - Supplying the appropriately maintained and certified equipment and Competent Persons (e.g. AP, driver etc) - Planning and documenting the lifting operations and ensuring that a safe system of work is in place - Organisation and control of lifting operations

    Management and planning

    Many tower crane collapses can be traced back to poor management and planning of tower crane operations.  The following elements are key to ensuring lifting is carried out safely and without incident.

    Safe system of work

    A safe system of work should be in place for all lifting operations and should include planning  of the operation, selection of a suitable crane and equipment, maintenance of the crane and equipment, preparation of  the site, provision of properly trained and competent supervisory personnel, ensuring all test certificates and thorough  examination reports are available, preventing unauthorised movement or use of the crane, provision for the safety of  all those involved or affected by the operation. The safe system of work must be embodied within a Lifting Plan.

    Selection and duties of personnel

    All those involved in a lifting operation must be competent, adequately trained and aware of  their duties. The duties of crane drivers, slingers, signallers, maintenance personnel etc, is detailed in BS7121-1. All crane drivers  should hold a CPCS card.

    Appointed Person (AP)

    The AP has overall control of the lifting operations and their duties should include:
    • assessment of the construction site environment and lifting operation requirements including planning, choice of  crane and equipment, and liaison with other parties affected by the lift
    • ensuring inspection and maintenance has been carried out
    • organisation and control of all lifting operations
    • briefing the Crane Supervisor on the contents of the method statement and Lifting Plan
    • ensuring there is an effective procedure for reporting defects and incidents and taking any necessary corrective action
    Some of the duties, but not the responsibilities, may be delegated for simple lifts. The AP should consult with other experts  including temporary works engineers and crane suppliers.

    Crane maintenance

    The crane should be in a satisfactory operating condition at all times. Planned maintenance and prescribed safety  checks should be undertaken with test certificates and documentation in place. Detailed requirements and checklists  are included in BS7121-2-5 and both LOLER and PUWER Regulations as well as detailed guides produced by the CPA,  including TCIG-0801.

    Pre-use checks, daily, weekly and in-service inspections/maintenance checks are essential and need to be recorded.  Key aspects to check during maintenance include, but are not limited to:

    • general condition of structures (e.g. fatigue cracks), fastenings, ties and machinery
    • operation of alarms, warning lights, indicators, motion limiters and cab accessories
    • brakes, including the weathervaning mechanism
    • slewing mechanism, control gear, safety devices, cables and pulley block
    • documentation and warning signs are present, etc.

    Thorough examinations

    Thorough examinations (TEs) need to be carried out at: specified intervals, after installation, after  major alterations or repair or after exceptional circumstances affecting the safety of the crane. LOLER specifies maximum  intervals between TEs are six months for tower cranes that lift people and twelve months for tower cranes that lift goods only.  It is, however, good practice to set the maximum interval for all tower cranes on construction sites at six months due to their  use in:
    • potential emergencies; to lift injured or trapped site personnel from buildings or shafts, etc
    • frequently lifting loads above or near people (site personnel and members of the public)
    • intense and rugged working environments
    TEs needs to be undertaken by a Competent Person and to a defined scope (see TCIG 0801 and 8.7.2 of BS 7121-2-5 for  a detailed list of components to be included).

    Contract lift vs crane hire

    An organisation that requires the use of a tower crane and does not have its own craneage  has two options - hiring a crane (Hired Crane) or employing a contractor to carry out lifting operations (Contract Lift).  If an individual or organisation does not have expertise in lifting operations, they should not hire cranes but should opt  for the contract lift option.

    Insurance arrangements should be clarified. A summary of the options is included in the following table.

    A useful best practice guide and pro formas on producing a risk assessment and method statement for a contract lift  is available from the CPA Crane Interest Group:

    Risk assessment and method statement

    An essential element of any crane operation is the production of a risk  assessment and method statement. The risk assessment should be carried out by the AP and identify the hazards and  risks associated with the lifting operation. Reference should be made to the overall site risk assessments included in the  CDM Construction Phase Plan. The AP should ensure that a full method statement is prepared, detailing the safe system  of work and control measures for the lifting operation. A Permit to Lift is a useful mechanism to ensure all pre-lift checks  are undertaken.

    Crane selection and access

    The choice of a suitable tower crane is governed by a number of factors, including: the  characteristics of the loads to be lifted (weight and dimensions), radii, heights of lifts, areas of movement, frequency and  types of lifting operations, length of time on site, construction site configuration and space available for access, erection,  operation and dismantling.


    The management, planning and execution of a crane lifting operation need to take into account many aspects.  Consequently, it is recommended that the use of checklists and pro formas are employed to ensure no aspect is left  unaddressed. These may include, but not limited to: key elements of the safe system of work, the load and the lift, the  location, specifying and operating teams, the crane, the lifting gear and any temporary works. Sample checklists are  included in C703. Periodic inspection checklists for a tower crane should be completed (see BS 7121-2-5 and CPA  document TCIG 0801).

    Siting of cranes

    The siting of a tower crane to ensure  its stability needs to be carefully  considered by the AP, taking into  account a number of aspects,  including:

    Alterations and construction work:  any alterations, including increasing  the height of the tower. Construction  activities required near to the base or  any ties to high-rise structures.

    Access, radius and height: sufficient  room for the construction of the  foundation and the installation and  removal of the crane. Requirements  for the maximum load, radius and  hook height.

    Vaults, basements or underground  services: the location of underground  services and adjacent structures on  which load could be imposed by the  crane foundation, e.g. retained  basements.

    Wind: the effect of wind both in and  out of service for a particular location,  e.g. cliff tops. Placing tower cranes in  free-slew mode when out of service  may avoid collapse events.

    Proximity hazards: these include  overhead electrical cables, nearby  structures, other cranes, railways  and flight paths. The appropriate  authority should be consulted if  any part of the crane cannot be kept  clear of such hazards or areas. Restrictions on oversailing should  be applied. The sequence of crane  movements should be planned by the  Crane Coordinator to avoid collisions  between other cranes and equipment.

    Tower crane foundations and support

    A suitable crane standing, support  or foundation base is essential for  the stability and safe operation of  the crane. The following aspects  are key to ensuring adequate  support is provided.

    Crane standing or support  conditions: the AP should ensure that  the ground, or any means of support,  can sustain the loads imposed by the  crane. This should be undertaken by a Competent Person and use the  loading data provided by the crane  manufacturer and include the most  severe combined effects of  the following:

    • the dead weight of the crane  including any counterweight, ballast  or foundation  
    • the dead weight of the load with the  addition of accessories used for  lifting
    • dynamic forces caused by movement  of the crane
    • loads imposed by wind and ice

    (Note: for guidance on suitable support  and controls for mobile self-erecting  tower cranes, see our guide to loss  prevention entitled ‘Mobile cranes  overturning on construction sites’  and  CPA guidance on the Safe use of  Self Erecting Tower Cranes.)

    Crane ties: where cranes are tied into  a building, the supports should be  included as part of the design. This will  involve liaison between the Competent  Person and the permanent works  designers. Ties should be inspected  before the crane goes into service to  confirm they have been installed to the  design specification, and an inspection  report produced. Following the  inspection, a permit to erect should  be issued by the responsible person.  Sample reports and completion  certificates are provided in BS 7121-2-5.  

    Expendable base: the minimum  dimensions for an expendable base  block should be provided by the  crane manufacturer. Given these  dimensions, along with the load data,  a Competent Person should design  a suitable foundation so as to ensure  that the ground bearing capacity  is not exceeded.

    Rail tracks: rail tracks should be made  of suitable material, not be used for  storage and be fenced off to prevent  unauthorised access. The tracks should  not be welded or subject to heating.  The end stops should be bolted or  pinned and be positioned such that  the crane makes contact on each stop  simultaneously. The end stops should  also be either buffered or shock  absorbing. Rail clamps should be  provided to prevent the crane rolling  along the track in storm conditions  or whenever it is out of service.

    Special bases: in some instances,  special base arrangements may be  required for example fixing to  structural steelwork on cruciforms  or grillages. The AP should ensure that  the base is designed appropriately  and verified by a third party Competent  Person, and constructed in accordance  with the design.

    Loading, erection, climbing and dismantling

    Poorly controlled loading, erection,  climbing and dismantling operations  can lead to tower crane collapse events.  These aspects need to be scrutinised  and managed by Competent Persons.

    Load components: tower cranes can  collapse as a result of lifting excessive  loads, overreaching, high winds and  swinging loads, which increase the load  radius and overturning moment.  Control measures include only lifting  pre-agreed weights, working within the  defined radius, monitoring and ceasing  work during high winds, and lifting  loads gently and smoothly to avoid  loads swinging. Loads should not be  dragged along the ground and side  loading of the jib should be avoided. A  rated capacity indicator/limiter should  be employed.

    Erection and dismantling: the erection  and dismantling of a tower crane  should be the subject of a specific risk  assessment and method statement.  The manufacturers’ instructions must  be followed to ensure stability  throughout the process and that  structural and mechanical parts are not  subject to excessive loading. Particular  attention should be paid to interim  stages where out of balance forces  from the jib or counterweights could  lead to collapse.

    Floor climbing: floor climbing cranes  are employed on tall buildings using  hydraulics and the permanent structure  for support. The arrangements are  specialised and need to be carefully  planned and executed by Competent  Persons. Liaison with the permanent  works designer is essential. Full details  and guidance are included in BS 7121-5  and CPA TCIG 1101.


    Statutory requirements: there are  many statutory requirements which  apply to lifting operations. The  following are the main references:  

    • The Health and Safety at Work  Act 1974
    • The Construction (Design and  Management) Regulations 1994  (as amended)
    • The Management of Health and  Safety at Work Regulations 1999
    • The Lifting Operations and Lifting  Equipment Regulations 1998  (LOLER)
    • The Provision and Use of Work  Equipment Regulations 1998  (PUWER)
    • The Supply of Machinery (Safety)  Regulations 2008 (as amended)

    In addition, a list of references and  guidance is included at the end of  this document.

    The table below provides a summary of typical hazards and suitable  control measures to mitigate the risk of collapse or failure of a tower  crane. The table does not necessarily include all hazards that may be  present, which should be identified by a site specific risk assessment.
    Collapse hazard Controls to mitigate the risk
    Failure of the ground and/or foundation base or support
    Incorrect support or foundation base specified The support or foundation base should be designed by a Competent Person taking into account load and soil data. An audit trail should be included in each crane maintenance log which details the support design, along with confirmation by third parties as to its suitability.
    Support or foundation base incorrectly constructed The audit trail for the support design should include a sign-off document that confirms the support or foundation base has been constructed as per the design.
    Management and planning failures
    Inexperienced supervisors and crane operator Ensure only competent, trained persons are employed (see BS 7121-1). Consider a Contract Lift if competence of supervisors is in doubt.
    Unclear roles and responsibilities Ensure key positions are established and individuals appointed by letter detailing their roles and responsibilities.
    Uncontrolled lifting operations Ensure all lifting operations are subject to a Lifting Plan including a risk assessment and method statement and a Permit to Lift.
    Collision Ensure that all lifting operations are planned with all proximity hazards identified. If multiple tower cranes are overlapping, then anti-collision devices should be installed.
    Load too heavy Ensure the load to be lifted is not greater than allowed for in the planning. The rated capacity limiter/indicator should be maintained in good order.
    High wind loading Establish site wind speed limits (red/amber/green). Use an anemometer to monitor in-service wind speeds and ensure maximum speed for crane configuration is not exceeded. Monitor weather forecasts and ensure the slew brake is disengaged during periods when the crane is non-operational (see HSE guidance
    Mechanical failure
    Poorly maintained crane/component fatigue failure Ensure crane is regularly maintained in accordance with the LOLER and PUWER Regulations and thorough examinations performed.

    Case study

    Two construction firms were  successfully prosecuted after a tower  crane collapsed onto a city centre  apartment block, resulting in the crane  driver suffering multiple injuries. The  tower crane was being used as part of  a multi-million pound project to build  a new hotel and apartment blocks.

    The HSE investigation into the incident  found that the crane’s foundation could  not cope with the forces generated by  the crane. During the construction of  the foundation, both the principal  contractor and the structural  engineering company agreed to cut  away essential steel reinforcement bars  from the four concrete foundation piles  to allow the crane feet to sit on them.

    The HSE identified serious failings by  both parties as having been responsible  for the collapse. The structural  engineering company had no previous  experience of designing the type of  crane foundation used and, likewise,  the principal contractor’s employees  had no experience of building one. Neither company did enough to check  what the result would be of cutting  away the essential steel reinforcement.

    Designers should be familiar with  industry accepted guidance and strictly  adhere to design information supplied  by tower crane providers. The role of  the principal contractor is also crucial  in managing the design process.

    Common terms and definitions

    Lifting Plan: a document providing  full details of a crane lift including  responsibilities, loads/safe working  loads, crane type, lifting accessories,  sequence of operations, hand signals  and radios, wind speed policy,  checklists, sketches, a risk assessment  and method statement, etc. This is a  legal requirement of Regulation 8 of  the LOLER Regulations and should be  formulated by a Competent Person.

    Permit to Lift: a formal process  recording checks and approvals prior  to confirming a lift may proceed.

    Thorough Examination: detailed  examination by a Competent Person  to determine if a crane is safe to take  into use or continue in use. This is in  addition to the maintenance regime.

    Appointed Person (AP): a key person  with the training, practical and  theoretical knowledge and experience  required to plan and manage a  lifting operation.

    Crane Supervisor: person who  controls the lifting operation and  ensures that it is carried out in  accordance with the AP’s safe system  of work.

    Crane Coordinator: person who plans  and directs the sequence of operations  of cranes to ensure that they do not  collide with other cranes, loads and  other equipment.

    Crane Operator: person who is  operating the crane for the purpose  of positioning loads or erection of  the crane.

    Slinger: person responsible for  attaching and detaching the load to  and from the crane and for the correct  selection and use of lifting accessories.

    Signaller: person responsible for  directing the crane driver to ensure safe  movement of the crane and load.

    References and Guidance BS 7121-1:2006 – Code of practice for safe use of  cranes ( BS 7121-2-5:2012 - Code of practice for the safe use  of cranes - Inspection, maintenance  and thorough examination - Tower cranes  ( BS 7121-5:2006 Code of practice for safe use of  cranes – Tower Cranes  ( CIRIA Publication C703:2003 – Crane stability on site  ( CPA/Crane Interest Group – Best Practice Guide for  Risk Assessment and Method Statement for a  Contract Lift: 2012 ( CPA/Tower Crane Interest Group – Maintenance,  Inspection and Thorough Examination of Tower  Cranes TCIG 0801  ( CPA/Tower Crane Interest Group – Safe Use of Self  Erecting Tower Cranes: 2010  ( CPA/Tower Crane Interest Group – The Climbing of  Tower Cranes TCIG 1101: 2011  ( Disclaimer: The guidance in this document refers to  industry best practice loss control advice. Adoption  of the advice contained within this document does  not imply compliance with industry, statutory or  HSBEI guidelines, nor does it guarantee that related  losses will not occur. HSB-LCE-RGN-009 Rev: 0 Date: 07/08/2014

    Construction insurance solutions and inspection services

    We have a comprehensive range of construction insurance products covering all aspects of projects across the UK and Ireland.

    Our engineering inspection services also help customers to maintain workplace equipment safety, optimise the efficiency of a vast range of plant and equipment, and comply with applicable health and safety legislation.