• These notes relate only to sewers and not to water mains.
• These notes relate only to building work which has already been carried out, and not to building work which is proposed to be carried out.
• These notes relate to both:

i. Building work which has been carried out over sewers

ii. Building work which has been carried out near sewers.

Unless otherwise indicated, in these notes ‘build over’ includes ‘build near’

Please note that the applicant is required to submit a Site Location Plan 1:1250 / 1:2500 map (LPSACE map will suffice) with the site boundary clearly indicated in red and relative to an existing feature to allow for the specified area to be easily identified. The area where information is required must be covered in full by the site boundary outlined in red on the site location plan.

There is a cost for this service in accordance with our current Scheme of Charges for a ‘Build Over Record Request’. Our records will be examined to determine if there is any record of a previous build over agreement within the area identified. If there is an existing build over agreement we will issue the applicant a copy of the agreement and no further action will be required. 

However, if no prior build over agreement can be found the next step in the process is completion of the ‘Retrospective Build Over Application Form’ for an extension which has been built over a sewer without prior consent from NI Water.

a. If it is determined that there is no build over agreement in place, the applicant will need to complete a Retrospective Build Over Application.

b. Date when building work was started:

i. For build overs which have been completed post 2007 a Retrospective Build Over Application must be completed. 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 cause any building to be erected over or in the vicinity of a pipe or sustainable drainage system vested in NI Water so as to have an effect on the use or operation of the pipe or system unless with the prior consent of NI Water.

ii. For build overs which have been completed between 1973 and 2007 a Retrospective Build Over Application must be completed. Article 41 of the Water and Sewerage Services (Northern Ireland) Order, 1973 states that any person who wilfully and without the consent of the Ministry (now NI Water), alters or interferes with any works vested in the Ministry for the purposes of this Order shall be guilty of an offence and shall be liable on conviction on indictment to imprisonment for a term not exceeding five years or to a fine or to both.

iii. Build overs completed prior to 1973 will not require retrospective consent.

c. Building Over or Near to Critical Sewers:

i. Critical Sewers are usually defined as large diameter strategic sewers but may also be classified by material, depth and/or location.

ii. Under no circumstances will retrospective consent be given where construction has been carried out directly over a critical sewer, manhole or pumping main. Restrictions WILL also apply as to how close you can build to such sewers.

iii. Please note: Although we will consider every case sympathetically, it is probable that a retrospective build over agreement for sewers which are classified as critical sewers will not be given.

d. Non-Critical Sewers:

In order to adequately assess the application it will be necessary to determine the exact location and condition of the affected sewer. In order to assess the condition of the affected sewer NI Water will complete a site inspection and CCTV survey (including desilt). Applicants will be required to expose pipework in order to determine if a full retrospective build over agreement can be considered. It may be possible to give retrospective consent in respect of structures built over non-critical sewers which often run along the back of older properties and are affected by extensions to the rear of the property. In most instances retrospective consent for building over/near these sewers will be given, provided that certain protective measures are taken. The standard protective measures that should exist are as follows:

i. Building Over (as opposed to Near) Non-Critical Sewers The standard protective measures that should exist are as follows:

1. CCTV Survey completed by NI Water to determine the condition and actual location of the affected sewer;
2. Foundations must have been taken down 150 mm below the sewer invert level.
3. Retrospective consent will not be given if any structures (footings, walls etc.) run parallel to the line of the sewer within 500 mm of the sewer (in plan); and
4. 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 Sewer ’on page 3)

ii. Building Near (as opposed to Over) Non-Critical Sewers

1. CCTV Survey completed by NI Water to determine the condition and actual location of the affected sewer;
2. Foundations must have been constructed below the sewer invert level.
3. Retrospective consent will not be given if any structures (footings, walls etc.) run parallel to the line of the sewer within 3.0 metres or 1.5 times the depth of the sewer (whichever is greater), unless by agreement of NI Water.

Please note:

• Northern Ireland Water may request a Structural Engineers Report at the developer’s expense.

Documents which should be included within the Retrospective Build Over Application should include:

• Site Location Plan 1:1250 / 1:2500 map (LPS ACE map will suffice) with the site boundary clearly indicated in red and relative to an existing feature.
• Site layout plan @ 1:100 or larger, showing location of existing sewer and manholes.
• Longitudinal Section showing pipe size and material.
• Foundation details of building (refer to ‘Typical Detail for Building Over Sewer’).
• Manhole details showing location and depth.
• Method Statement (including details of calculations and piling system, if applicable).

Enquiries should be addressed to:

Developer Services - Servicing Team

Northern Ireland Water

Ballykeel Office

188 Larne Road

Ballykeel, Ballymena

Co Antrim 

BT42 3HA

Telephone: 03458 770 003

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/