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Oversailing: what is it and why is it a concern for developers?

On a tight construction site, use of a tower crane may be the most practical construction method for maximising the footprint of the building and the efficiency of its construction. Developers and their contractors should however be aware of certain key issues likely to flow from use of tower cranes, particularly in densely populated areas:

  • Under English law a landowner owns the airspace above his land (unless it has been expressly excluded from the lease or transfer to him) and it is therefore trespass if a developer or its contractor allows a tower crane jib to swing across land owned by other parties;
  • An adjoining owner can obtain an injunction to prevent such trespass without needing to show that any damage has occurred;
  • The developer and/or its contractor should seek a licence from third parties whose land may be oversailed by a crane, permitting the trespass and setting out the terms of use of the tower crane.


The use of tower cranes is now commonplace on constructions sites as providing height and lifting capacity, but (and this is particularly important in city centre developments with a small site area) occupying a minimal footprint on the site.

An inevitable consequence of the use of tower cranes on city centre sites is that the jib of the crane will oversail adjacent sites. Even if the operation of the crane can limit the swing of the jib, safety and structural stability require that when the crane is not in use the jib must be left to swing in the wind, giving a circle of oversailing with a radius equal to the length of the jib from the mast of the crane. Any property within that circle will potentially be oversailed.

The legal context

The basic principle of English law is that a landowner owns all the airspace above the land, to the heavens above. Legislation has given aircraft rights to pass without causing any trespass, but the basic principle holds good nearer the ground. This means that the jib of a tower crane swinging across land owned by an adjoining landowner is trespassing.


If no authority to oversail adjacent properties has been obtained then the developer or the contractor may be faced with injunctions from the adjacent landowners, preventing the oversailing, and hence fundamentally impacting the contractor’s construction methodology. There is case authority1 that an injunction for trespass can be obtained without having to demonstrate any damage, the basis is simply that property rights are being violated.

As with so many development constraints, the key is to address them early enough. In this case, the developer and its advisers can consider the size of tower crane likely to be required, to assess the radius of the likely swing of its jib, and then to approach all landowners whose property may be oversailed to seek their permission to do so, which will be documented in a crane oversail licence. It should be noted that the highway authority is a landowner for this purpose, usually with specific requirements in relation to any oversailing of the highways, predominantly aimed at ensuring public safety. It should also be noted that for the purpose of an oversailing licence, the agreement of both landlords and tenants of the relevant adjoining land may be required.

Oversail licence

So what provisions would generally be included in a crane oversail licence?

  • Permission to oversail the land, usually by reference to plans showing the agreed location of the crane and anticipated turning circle of the swing of the jib.
  • Limit on duration to the carrying out of the particular development, probably with an element of contingency for delays.
  • An indemnity from the developer and/or the contractor for any damage to property or personal injury or death arising from the oversailing, backed up with an appropriate level of public liability insurance.
  • Reference to a method statement either already in existence or to be put in place dealing with construction, operation and dismantling of the crane, probably also referring to the Construction Plant Hire Association’s Codes of Practice and the Health & Safety Executive’s requirements under their Tower Crane Regulations.
  • Reference to compliance with all relevant laws, including but not limited to those relating to health and safety.
  • Provision for termination of the licence in the event of material breach of its terms or insolvency of the developer and/or contractor.

What about a fee?

Adjoining owners may seek a fee to grant the oversailing rights a developer and its contractor need, in addition to payment of the adjoining owner’s costs of putting the licence in place and any other associated fees. Whilst this could be seen as a ransom opportunity for an adjoining owner, in practice case law2 has restricted this. Where a contractor has offered a substantial fee for grant of an oversail licence and had this refused by the adjoining owner, this may inhibit that adjoining owner then seeking an injunction to prevent oversailing, for example resulting in the court awarding an injunction (as trespass is clearly occurring) but then suspending its operation for the duration of the development period, i.e. in effect granting the developer the rights it requires.

This begs the question of what would be considered an appropriate licence fee. There is no specific formula (though certain highway authorities do have set fees for oversailing the roads), but the fee needs to take into account the impact of the use of the tower crane on development costs, compared with the use of other construction methods, and any costs of the adjoining owner arising from the arrangements.

Other considerations?

As an adjoining owner, approached for the grant of a crane oversail licence, consider your own future development plans. Now may be the time to secure your own arrangements for the future by making the crane oversail arrangements mutual. Such a mutual arrangement may in practice be far more valuable than receiving a fee for the licence currently requested.

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