Please refer to the Declaration of Works process before completing this form
Application to build over/near Public Sewers (Building Regulations 2010 – as amended)
Within the Southern Water region there are approximately 39,000 kilometres of public sewers, some of which may have been laid within the boundaries of properties. As the sewerage undertaker, Southern Water is responsible for the maintenance of this pipework. You must get our agreement to carry out any building work over the top of or within three metres of a public sewer to ensure that no damage is caused to it or restrictions made to the way we use and maintain the sewer.
Through recent amendments to the Building Regulations, local authority building control departments and approved inspectors (NHBC etc) are responsible for controlling building over public sewers that are:
- 225mm in diameter or less; and
- Less than three metres deep; and
- Where less than six metres of the public sewer is to be built over; and
- Access to the public sewer is unimpeded.
Building over existing sewers on new development sites
or re-development sites is not permitted.
You will need to satisfy building control that your proposals will not have an adverse effect upon the public sewerage system. Whilst they must consult with Southern Water and have regard to any views expressed, ultimately it is they who must approve or reject your application having taken into account all the risks and requirements relating to building over or adjacent to sewers as contained in paragraph H4 of the building regulations.
They have a duty to reject the plans unless they are satisfied that they may properly consent either with or without conditions.
However, it will usually help speed up your building regulations application if we are already aware of your proposals.
- Prevent damage to the sewer – the additional weight of new buildings could cause the sewer to collapse, resulting in structural damage to the building, interrupted drainage from other properties and increased risk of sewage flooding. The sewer would have to be repaired immediately, even if it involved demolishing the building.
- Access for maintenance and repairs – Southern Water requires 24-hour access to all sewers and manholes to carry out routine inspections, maintenance and repairs.
How can you find out if there is a public sewer on the land?
Visit your local authority and inspect a copy of the sewer map.
Mains and sewer maps can be provided upon request (fees apply).
Sewer and Water Maps
The maps identify the location and size of known public sewers and water mains in the locality of the property or land.
Request a map online using digdat®, or arrange an appointment to view at our Durrington office in Worthing.
If there is a sewer, how could this affect the building proposals?
There are two options that should be considered.
Modify the plan
To avoid the sewer, so that buildings are at least three metres away. This is often the cheapest and easiest option.
Divert the sewer
If the plans can not be modified, the sewer may need to be diverted. The work will be carried out by Southern Water, but at your expense. Estimated costs will be given and agreed before any work commences.
Building over applications.
If having considered all the alternatives the only option appears to be to build over the public sewer and the sewer in question is 225mm diameter or less than three metres deep and you should forward your proposals to building control.
In order to adequately discharge its duty under the new regulations it will be necessary for building control, or you, to determine the exact location and condition of the affected sewer(s). (Please be aware that you will need to obtain our permission before carrying out any survey works on the public sewers).
Where this is not possible Southern Water may be willing to carry out the location and condition survey and appraise your plans. However, this will be at your expense.
The current fee associated with this service is as per the application form:
– Plan appraisal and administration fee
– CCTV survey and site visit by clerk of works if required
Although we will consider every case sympathetically, it is probable that permission to build over a sewer which is greater than 225mm diameter and/or three metres deep will not be given.
It is, therefore, in your interest to contact us in the preliminary design stage in order to avoid abortive costs, delays or other problems.
It may be possible to build over sewers less than 225mm diameter and less than three metres deep (minor sewers), such sewers often run along the back of older properties and are affected by extensions to the rear of the property. These are not uncommon in properties built before October 1, 1937. In most instances building over/near these sewers will be permitted, providing that certain protective measures are taken. The standard protective measures are as follows:
The affected length of sewer should be replaced using ductile iron pipework. Alternatively a CCTV survey (see below) will be required to determine the condition and actual location of the affected sewer.
Foundations must be taken down 150mm below the sewer invert level. No structures (footings, walls etc) running parallel to the line of the sewer will be allowed within 500mm of the sewer (in plan).
Crossings must be supported using pre-cast (or adequately designed cast in-situ) concrete lintels/beams.
Building near minor sewers
Foundations must be below the sewer invert level. No structures (footings, walls etc) running parallel to the line of the sewer will be allowed within 500mm of the sewer (in plan).
The exact location and condition of the affected sewer will need to be determined.
Building close to critical sewers
Critical sewers are usually defined as large diameter strategic sewers but may also be classified by material, depth and/or location.
Under no circumstances is construction allowed directly over a critical sewer, manhole or pumping main. Restrictions may also apply as to how close you can build to such sewers.
Piling works near sewers
Where piling works are being carried out care must be taken to avoid any damage to the public sewers. The position of the sewer should be established by electronic survey. Should the survey suggest that the sewer is likely to be within two metres of the piling, trial holes must be excavated to establish the exact location of the sewer.
Any incomplete application form received will not be processed until all relevant documentation is received by Southern Water. In most circumstances we are able to give you a decision within four weeks of receipt of a complete application.