Declaration Of Works

Building over (or close to) a public sewer (minor) or lateral drain

325050 A-DEVSRV-SN18

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The first thing to do is check if your new building is subject to the Building Regulations. If it is then you may be able to utilise our Building Control Protocol Agreement through your building control inspector and you will not need to fill in this form. For more information please see read through our guidance notes in section A:

It should be noted that:

Building over or close to public water mains, pumped or vacuum sewer mains is never permitted.

Building over or close to existing sewers on new development sites or re-development sites is never permitted.

If your proposed extension/building is not subject to Building Regulations, or you are not in a protocol area the following guidance will help you to fill out the Declaration of Works application. If your proposals meet the requirements for self certification consent to build over will be provided by letter. See attached tables below.

Within the Southern Water region there are approximately 39,000 kilometres of public sewers, some of which have been laid within the boundaries of properties. As the sewerage undertaker, Southern Water is responsible for maintaining this pipework. In order to comply with the legislation relating to building over/close to and the diversion of public sewers it is necessary for anyone wishing to develop land or extend their property to consult with Southern Water to ascertain its requirements for dealing with any lateral drains or sewers that are likely to be affected by their building proposals.

How can I find out if there is a public sewer on the land?

  • Visit your local authority and ask to view a copy of the sewer map; or
  • Write to:
    Southern Water Services Limited, LandSearch,
    Southern House, Capstone Road, Chatham, Kent,
    ME5 7QA

Please state the property address and address to which the plan should be sent together with a cheque for £48.00 (incl 20% VAT) payable to Southern Water Services Limited

We require details of proposals Approval will be given subject to:- Formal application to submitted for consent required Application will be deemed unacceptable
X Your development involves the construction of a new residential property, the extension of industrial and commercial property or any detached ancillary buildings or structure

X The pipe diameter, direction material or gradient changes beneath the area of the proposed build

X The size of the pipe is 300mm in diameter or larger

X Detached ancillary buildings or structure

X If you are unable to relocate the access point, i.e. access is on junction of sewers or a change of direction

X Your proposal involves an infill structure from one boundary to another where there are already structures on both sides

X Pressurised pipes such as rising mains and water mains
You have had reason to contact Southern Water or another drainage professional as a result of problems with the sewers or lateral drains within your property within the last 12 months and these have not been repaired as yet
You are aware of easement/covenants which relate to the pipework which you propose to build near/ over You are aware of easement/covenants which relate to the pipework which you propose to build near/ over
This can potentially be resolved if the sewer can be diverted and the customer is prepared to enter into Sewer Diversion Agreement in accordance with S.185 Water Industry Act 1991. The pipe is a pressurised main
If the pipe has an internal diameter of 150mm (6 inch) or less, consent will be issued via letter, if approved. If the pipe’s internal diameter is 225mm (9 inch), consent will be issued via agreement, if approved If the pipe’s internal diameter is larger than 225mm (9 inch)
Non-compliant pipe material can potentially be resolved if the pipework is replaced before building works begin Pitch fibre, brick, asbestos cement, plastic not able to withstand 4000 psi jetting pressure
Poor pipe condition, which can be resolved if the pipe is repaired or replaced The pipework is found to be defective and is not repaired
Minor pipe inconsistency can potentially be resolved by carrying out agreed minor amendments before building works begin Diameter, direction, material or gradient clearly changes beneath (or close to) he proposed new building
Consent for building works over or near sewer and lateral drains which are deeper than 3m, will be issued via agreement or money in lieu. Please fill in the build over Application Sewer depth is greater than 3 metres
Inaccessible access point issue can be resolved if the affected access can be repositioned or the shape of the build/extension is adjusted to meet this requirement. You are unable to meet the minimum 500mm clearance requirement or the existing access will be under the new building
If you intend to build full width of the garden and there is no external access to the sewer then consent will be issued via agreement. Any existing access points will need to be maintained by carrying out agreed minor alterations. You intend to build across the full width of your garden and your neighbours have also done the same.
A detailed assessment of the foundation and its impact may be needed. Consent issued via Agreement Your building will use another form of foundation design e.g. pad, piling, raft, cantilever, etc.
This can potentially be resolved after a detailed assessment of the foundation and its impact on the pipe. Consent issued via Agreement Your foundation design cannot achieve 500mm clearance from the pipe or does not satisfy detailed design assessment criteria
Alternative foundation proposals will require a consent issued via Agreement Required foundation depth cannot be achieved
The minimum lintel requirements cannot be achieved
Insufficient vertical headroom can potentially be resolved if the sewer can be diverted and the customer is prepared to enter into Section 185 Sewer Diversion Agreement Water Industry Act 1991 Your design cannot provide 300mm of headroom between the underside of the new floor and the pipe and the sewer diversion option is not practicable.

Building over sewers

If the proposals do not meet the self-certification points, a build over application form can be downloaded from the following link:

Diverting an existing public sewer

If the affected sewer requires a diversion (relocation not replacement of existing line) you will be required to submit a Section 185 application to Southern Water Services:

What are the standard protective measures?

The attached drawings show the permitted locations of foundations in relation to existing and proposed sewers

  • In all cases a CCTV survey or exposing the sewer will be required to determine the exact location and/or condition of the affected sewer.
  • Should the survey or exposing the sewer show that the affected length of sewer is not in a suitable condition to be built over and/ or has a non-compliant pipe material of either pitch fibre, asbestos cement or plastic which is not able to withstand 2700 psi, it must be replaced, at the applicant’s expense with Southern Water certified pipework that is capable of withstanding the required jetting pressure.
  • Foundations that are to be built within 3 metres of a minor sewer must be taken down to 150mm below the invert level of the affected sewer or lateral drain;
  • No structures (footings, walls etc.) running parallel to the line of the sewer should be built within 500mm of the sewer (distance measured on plan i.e. in the horizontal);
  • Any crossings of the sewer must be supported using adequately designed pre-cast or in-situ concrete lintels/ beams.

Piling works for Foundations

  • Where piling works are proposed the position and condition of the sewer should be established by means of electronic survey. Should the survey show that the sewer is likely to be within three metres of the proposed piles, trial holes must be taken to establish the exact location of the sewer. The piling method e.g. percussive/driven or auger bored and the acceptable distance of the piles from the sewer must be agreed with us prior to the commencement of any work on site. Upon completion of the works a further CCTV survey may be required to ensure that the sewer has not been damaged during the piling operation.
  • It should be noted that where piling works are to be carried out care must be taken to avoid any damage to the public sewer. Should the survey suggest that the sewer is likely to be within 2 metres of the piling, as in this case, trial holes must be excavated to establish the exact location of the sewer? No piling should be permitted within 1.0m of the sewer.  No driven or percussive methods of piling works will be accepted within 3.0 metres of the existing public sewers. Detailed plans and the type piling works to be utilised will be have to be submitted to this office for approval. A repeat CCTV survey will be required on completion of the works to confirm that no damage has been caused as a direct result of any piling works.

Where a public sewer is to be built over its must be in a good condition and in an approval material. (It must be able to withstand a jetting pressure of 2700 psi, stated in (MED 4006 , the Southern Water supplement addendum to Sewer for Adoption 7 th Edition) )

Southern Water approved* materials are:

  1. Vitrified Clay(VC).
  2. Ductile Iron (DI).

The following foundations types over the public sewer are not normally permitted

  • Pad
  • Raft
  • Cantilever foundation
Southern Water does not normally permit this type of foundation as future access to maintain the public sewer and could impact the proposed structure.

On the 1st October 2011 responsibility for private gravity sewers and lateral drains that were constructed and communicating with the public sewerage system prior to 1st July 2011 was transferred to Sewerage Undertakers such as Southern Water. As a result of the transfer, the number of sewers and lateral drains for which Southern Water is responsible has increased by approximately 19,000 km. Many of the transferring sewers and lateral drains had not been mapped and consequently their location and condition is unknown. Due to the absence of detailed information about the transferred sewers and lateral drains it must be presumed that they will be present within gardens and in land to be developed and are therefore likely be affected by any building proposals. You should therefore assume that any sewerage that is currently located on your land or which is discovered during the course of your work is public apparatus and in the ownership of Southern Water unless it can be shown to be otherwise.

Please check your site is in the Southern Water catchment area:

confirm that I have power of attorney to act on behalf of the legal owners of this property (Please provide a copy of the power of attorney with this application form).


(You MUST confirm all the statements below one true)





  • Copies of all drawings submitted for building regulations approval
  • Site location plan (1:1250 or larger)
  • Site plan (1:100 or larger showing location of sewers and manholes)

  • Site boundary clearly shown
  • Roads clearly shown
  • Adjacent buildings clearly shown
  • Private pipe run to Southern Water network clearly shown
  • Maximum file limit is 50MB
  • Allowed file types are DOCX, DOC, PDF, XLS, XLSX, JPG, JPEG, BMP, PNG, DWG (auto cad), DXF (auto cad), DGN (microstation), PRP (microstation), PRW (microstation)
Warning! File size too big. Maximum file size 50MB.

Please provide the following where applicable and tick the box if enclosed:

Payment enlcosed for Declaration of Work
I have read and understood the guidance notes
My Builder/Contactor will carry out the minor alterations

I accept that this application does not grant planning or building regulations approval for the proposed extension. No works should commence on site until such time written approval has been given by Southern Water Services.

I agree, that for purposes of the Water Industry Act 1991 and the Data Protection Act 1998, that the information provided for this application and all accompanying documents, may be held electronic or other records such as, computer systems and processed by Southern Water Services and its employees and agents for all purposes connected with the Company's statutory water and sewerage undertakings.

Failure to include any of the requested information will be deemed as an incomplete application and may result in this application being delayed/returned. This application DOES NOT mean approval has been granted. No work should commence until written approval has been given by Southern Water.
The contents of the report are for direct use only by the applicant and are to be kept private and confidential. They may only be disclosed to third parties with the written approval of Southern Water. Such third parties to have no subsequent implied or other right to disclose the contents and information to any other parties.
Amount to pay
Application Fee (Declaration of works)
£ 85.00
Inspection of minor alterations works undertaken by your own contractor/builder
VAT (20%)
£ 17.00
Total Fee
£ 102.00
Do you require a VAT receipt?: *
Preferred payment method:
Application number:
Amount to pay: £ 102.00

Payments can be made directly via BACS transfer to:

Southern Water Services Ltd
Miscellaneous Income Account
HSBC Bank Plc
P O Box 125, 2nd Floor, 62-76 Park Street,
SE1 9DZ, London, England

Sort Code - 40-02-50
Account No - 81426834

(However please ensure that you confirm the application number you are making payment for in the reference line)

Please make cheques payable to Southern Water Services Ltd.
Your printed slip and cheque should then be sent to:

Miscellaneous Income
Southern Water
PO Box 4056
BN13 3XX

Please click on ‘Print Preview’ and confirm your cheque number is on the preview slip.
Please print the slip and attach the cheque after writing the application number on the back in case they are separated.