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Close Proximity to Assets (Water & Sewers)

Building Over or Near a Public Sewer

Building Over or Near a Public Sewer

BUILDING OVER OR NEAR A PUBLIC SEWER PROCESS

The Process
Step 1 -Application & Payments
Please complete the application form and send it to developerservices[AT]niwater[DOT]com with all of the associated documents listed on the application form.
Your application submission will be checked for completeness and you will be issued with details of how to make the payment of the application fee via BACS.
Please complete the application form and send it to developerservices[AT]niwater[DOT]com with all of the associated documents listed on the application form.
Step 2 - CCTV Survey (for building over and piling works only)
If it is proposed that the affected public sewer is not going to be replaced, we will carry out a CCTV camera survey to check the public sewer’s structural condition. If the affected public sewer is a Clay pipe it must be replaced at the property owner’s expense.
Step 3 - Assessment and Outcome
If your proposal is acceptable we will issue a Build Over / Near a Public Sewer Agreement and approval letter.
If any drainage works are necessary (eg, sewer replacement or manhole relocation), our approval will be conditional, pending completion of these works.
Step 4 - Owner to return signed Build Over / Near a Public Sewer Agreement 
Please return the Agreement with all of the required signatures to developerservices[AT]niwater[DOT]com
NIW will authorise the Agreement and will issue it to the applicant.
Step 5 - Drainage Works (amending NIW infrastructure)
The drainage works should be carried out in accordance with the agreed Method Statement and as detailed in the approved drawings.
Step 6 - Construction
Your works can commence.
When construction has progressed where the pipe protection measures have been installed and remain exposed, please submit an application for an Inspection (SBO-A236-Insp) inclusive of the inspection fee.
NIW will arrange for an Inspection of the work associated with the approved Agreement, inclusive of a CCTV to determine the structural integrity of the affected sewer.
If the work associated with the approved Agreement is deemed satisfactory we will issue a Completion Certificate as confirmation, to keep with your property deeds.

Guidance Notes

It is an offence under Article 236 of the Water and Sewerage Services (Northern Ireland) Order 2006 (as amended Water and Sewerage Services Act (Northern Ireland) 2016), to realign, build over or near watermains, public sewers, pipes and associated works owned and maintained by Northern Ireland Water unless with the prior consent by NI Water.

If you have located or have reason to believe that a public sewer is within the Protected Strip, which is noted as

  • within 3m or 1.5 times the depth of the proposed structure (whichever is the greater); OR 
  • within 15m if piling is proposed; OR
  • if your proposal involves the reduction or increase of the existing ground level within the Protected Strip, and construction of any building / structure (this includes any non-habitable structures, ie retaining walls) is proposed  within the Protected Strip you MUST consider relocating your building / structure.

You must consider the realignment of the public sewer in the first instance. Please refer to the Realignment of a Public Sewer guidance notes. If however, a realignment is not feasible due to site constraints, please provide evidence of the reasoning behind this decision when making the application to Build Over / Near the Public Sewer and include it in your application pack.

If you have considered all the alternatives and the only option appears to be to build over or near the public sewer, please forward your proposals to us for assessment using application form SBO-A236.

Please note that a Building Over / Near a Public Sewer Agreement may not always be permissible.

It should be noted that Northern Ireland Water will not consider a proposal to build over a public sewer for a new building.

Please determine the exact location of the affected public sewer(s) prior to making a Build Over or Near a Public Sewer application, as failure to do so may result in a delay in the processing of your application.

Where this is not possible Northern Ireland Water may be willing to determine the location on site. However, this will be at your expense. To avail of this service please email a location plan to waterline[AT]niwater[DOT]com to request the location of the public sewer to be identified on site.

The current fees and charges associated with the Building Over or Near a Public Sewer process, in accordance with the current Scheme of Charges are:

  • Application Fee - this includes appraisal of your proposals (non-returnable);
  • Inspection Fee - payable at the time of submitting the Inspection Application (SBO-A236-Insp) on completion of the work.
  • Request for NIW to locate the public sewer on site - if applicable.

Please note:

Although we will consider every case sympathetically:

  • it is possible that permission to build over public sewers which are classified as critical public sewers may not be given.
  • it may not be possible to permit a build over / near a public sewer if ground levels are being altered on site.
  • it may not be possible to permit a build over / near a public sewer if future maintenance access to NIW assets in the locality are diminished.
  • Under no circumstances is construction allowed directly over a pumping main. Restrictions WILL also apply as to how close you can build to such public sewers.
  • Manholes, were possible must be outside the structure. Where this is not possible, they must be sealed at finished floor level and accessible without excavation. Any floor coverings that will need to be removed for access purposes will be replaced at the owner’s expense. 
  • Inspection chambers MUST NOT be constructed on the line of the public sewer.
  • Lateral connections, where possible, should connect to the public sewer outside of the structure.

Permitted Location of Sewers and Lateral Drains in Proximity to Buildings or Structures

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Building Over Non-Critical Public sewers

It may be possible to build over non-critical public sewers, which often run along the back of older properties and are affected by extensions to the rear of the property. In most instances building over/near these public sewers will be permitted, providing that certain structural protective measures are taken. The standard protective measures are as follows:

  • CCTV Survey will be required to determine the existing condition and location of the affected public sewer;
  • Foundations must be taken down to a minimum of 150mm below the public sewer invert level. No structures (footings, walls etc) running parallel, or adjacent to the line of the public sewer will be allowed within 500mm of the public sewer (in plan); and
  • Crossings must be supported using pre-cast (or adequately designed cast in-situ) concrete lintels/beams. (Please refer to the ‘Typical Detail for Building Over a Public sewer’ on page 5)
  • Any clay or damaged public sewer under the proposed building MUST be replaced with a new sewer pipe of an equivalent size (material to be agreed with NIW). A detailed method statement will be required.


Building Close to Critical Public sewers

  • Critical Public sewers are usually defined as large diameter strategic public sewers but may also be classified by material, depth and/or location.
  • Under no circumstances is construction allowed directly over a pumping main. Restrictions WILL also apply as to how close you can build to such public sewers.

Piling Works Near Public sewers (within 15m of a public sewer)

Where piling works are being carried out care must be taken to avoid any damage to the public sewers. The position of the public sewer MUST be established by electronic survey. Should the survey suggest that the public sewer is likely to be within 15 metres of the piling works, trial holes may be required to establish the exact location of the public sewer. Piling systems must be chosen so that resultant vibration is kept to a minimum and a suitable method statement, inclusive of the measures to be taken if the public sewer is damaged, must accompany the application. 

Applying for a Building Over or Near a Public Sewer Agreement

  • You must submit the application form SBO-A236 via email to developerservices@niwater.com including all of the required information. 
  • Northern Ireland Water Ltd asks for details of:
    • Any mortgage on the property: 
      • in order that we can ensure that the mortgage company joins into any build-over agreement, to avoid a situation where they do not do so and they subsequently repossess the property and sell it  on. If this happened, the mortgage company and the subsequent purchaser could say that:
        • they (in the case of the mortgage company) or the mortgage company from whom they acquired  the property (in the case of a subsequent purchaser) had not signed or been aware of the  buildover agreement.
        • the buildover agreement was not therefore binding on them.
      • The house insurance ( must include buildings cover): 
        • as any home insurance company would want to be informed that the homeowner was entering into  an agreement with NIW to build a structure over or near a public sewer in relation to a property  which was insured with them.
  • Typical requirements for the associated documentation are:
    • The drawings(s) should include: 
      • Site Layout:
        • Be at a scale of 1: 100 or greater.
        • Show the location of existing public sewers and MH’s: 
          • Foul to be shown in red. 
          • Storm to be shown in green. 
          • Combined to be shown in magenta.
        • Show the extent of existing buildings and the proposed new construction (and any other  structures that may cause a loading on the public sewer).
        • Indicate changes in Ground Levels.
        • Existing public sewer replacements, to include tie in details to the remaining public sewer.
      • Longitudinal Section:
        • The sections should show:
          • Pipe size. 
          • Gradient. 
          • Material.
          • Manholes.
          • Invert Levels and Cover Levels to Ordnance Datum Belfast. 
        • Existing public sewer replacements, to include tie in details to the remaining public sewer.
      • Protection detail at crossover / potential loading locations:
        • This detail should be site specific, detailing the structural protection to prevent loading on the  public sewer.
      • Please include the floor construction method if the proposal is to build over the public sewer:
        • if it is proposed to have a concrete floor, only suspended concrete floors will be permissible.
    • The drawings should only show details that are relevant to the application, ie: 
      • The location of the proposed Build over/ near in relation to the public sewer. 
      • The proposed protection detail specific to the proposal. 
      • The public sewer with the colour coding as listed above with any private drainage shown in black.
    • If it is proposed to replace the pipe or construct a manhole on the public sewer you must submit a Method  Statement for the work.
    • If you are not proposing to replace the pipe, a Method Statement will be required in case the public sewer is  damaged during the construction process.
  • Your application will be checked during a triage process and if incomplete will not progress until such times as all of the requested information has been received. 
  • Once your application has completed the triage process you will receive a request for payment. 
  • On receipt of payment your application will be assigned to a Wastewater Approvals Technical Adviser

Building Over or Near a Public Sewer Agreement

Once the Wastewater Approvals Technical Adviser has assessed your proposals and agreed the associated detailed design drawings, they will issue a Building Over or Near a Public Sewer Agreement via email.

When you receive the Building Over or Near a Public Sewer Agreement 

  • you will be required to print it and gain all of the necessary signatures prior to scanning and emailing it to developerservices@niwater.com.
  • if there is any loan / mortgage on the associated property, the Loan / mortgage provider MUST sign the Building Over or Near a Public Sewer Agreement prior to it being returned to NIW.
  • you must hold and provide current Home Insurance details which must include buildings cover.
  • No work must commence on site until the Assessment and authorisation of the Building Over or Near a Public Sewer Agreement has be completed and the authorised Agreement returned to the applicant.

Completion of the works

  • You MUST submit an SBO-A236-Insp inspection application form to developerservices@niwater.com to request a site inspection, allowing 10 working days’ notice.
  • NIW will triage the inspection application, and if all of the required information has been provided will issue a request for payment of the Inspection Fee. 
  • On receipt of the Inspection Fee your application will be assigned to the Wastewater Approvals Technical Adviser who will be in contact to arrange a mutually suitable date for the inspection.
  • Any excavation and structural protection to the public sewer must not be backfilled or covered until inspected by NIW. If the excavation has been backfilled, you must excavate the locations of the structural protection prior to the agreed inspection date.
  • If the works are deemed to be satisfactory you will receive a copy of the Final Certificate of Satisfactory Completion of the Building Over / Near a Public Sewer along with a stamped copy of the associated As Constructed drawing.

Please note:

  • Northern Ireland Water may request a Structural Engineers Report at the developer’s expense.
  • Multi-applications with the same owner / lender for proposed building over proposals that are in the same location and on the same public sewer leg will attract a discount for third and subsequent applications. However each property will be processed under a separate Building Over or Near a Public Sewer Agreement, with the associated Inspection fee. Further Details are available in the current Scheme of Charges and the application form. 
  • Multiple properties with different owners/lenders must have a separate application.

Further Information

Should you require any further information or assistance please contact Developer Services Servicing Team

Telephone:03457 44 00 88

Email: developerservices[AT]niwater[DOT]com

For more information on how NI Water lawfully processes personal data please view our Privacy Notice at; https://www.niwater.com/privacy/



Typical Detail for Building Over a Public Sewer

  • It should be noted that Northern Ireland Water will NOT consider a proposal to build over a public sewer for a New Building.
  • The detail indicated below does not cover all situation which may arise on site and consultation may be necessary with representatives from Northern Ireland Water prior to submitting their proposals along with the application for consideration.
  • A Building Over or Near a Public Sewer agreement is required if the construction is within the Protected Strip, which is noted as
    • within 3m or 1.5 times the depth of the proposed structure (whichever is the greater); OR
    • within 15m if piling is proposed; OR 
    • if your proposal involves the reduction or increase of the existing ground level within the Protected Strip,

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  • Although we will consider every case sympathetically, it is probable that permission to build over sewers which are classified as critical sewers will not be given. 
  • Further information and application forms are available on www.niwater.com/servicesfordevelopers.asp 
  • This sketch is not to scale.

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