Thames Build-Over Agreement

In this blog, Icon Surveyors will be considering what a Thames Build-Over Agreement is and whether one is required to be included within a Party Wall Award.

What is a Thames Build-over Agreement?

In the simplest of terms,

A "Thames Build-Over Agreement" is agreed permission from Thames Water carry out building works that are over or within 3 meters of a drain, disposal main or sewer that is owned by Thames Water.

Under the Water Industry Act 1991, Thames Water, acquired all of the public water sewers in their region. Thames Water is therefore responsible for the maintenance of the sewers and drains that lead to them.  In order to maintain and protect the sewerage system effectively, Thames Water and/or its agents must be able to gain access to all of its drains, pipes, and sewers at any time. It is also necessary to ensure that none of the work proposed to be carried out will cause any damage.

When are the Thames Build-Over Agreements applicable?

Under Part H4(1) of the Building Regulations 2010, there is a legal requirement for a building owner and/or his agent to ensure that any works being carried out are executed in a way “that is not detrimental to…………….the continued maintenance of the drain, sewer or disposal main.”  Section H4(2) further provides that a "disposal main" is any pipe, tunnel, or conduit that is used to transport waste to or from a sewage disposal works, which is not a public sewer.

This legal requirement only applies to works that involve the erection or extension of a building or works that include the underpinning of a building being carried out over a drain, sewer or disposal main that is shown on any map of sewers. (Thames Water areas are contained in Schedule 2 of the Water Act 1973.) The requirement also applies to any work that would cause any type of interference with the use of or obstruction of access to any person that may require it.

In other words, if a building owner is building a structure, extension or carrying out works that involve underpinning, the works and materials used cannot overload or cause damage to a drain, disposal main or sewer prior to, during or after the works have been completed. This is because either extra weight or the positioning of a new structure that is located within 3 meters of a sewer could cause it to collapse. Nor can a building owner prevent reasonable access to the owner of any manhole or inspection chamber on a drain, disposal main or sewer.

Does a Thames Build-Over Agreement need to be included in a Party Wall Award?

In line with the 3-meter rule under the provisions of the Party Wall etc. Act 1996, any building owner who proposes to carry out works as described under Part H4 of the Building Regulations 2010, that is within 3 meters of a drain, disposal main or sewer is legally required to obtain consent from the sewage undertaker, in London and the Greater London area, this is usually Thames Water.

As can be seen in the preceding paragraph, the Party Wall Act will be engaged if the party wall 3-meter rule applies to the work being carried out.

If, and only if, a Party Wall Surveyor has been engaged in accordance with section 10 of the Act, will section 10(12) of the Act? Section 10(12) of the Act provides what should be included in a Party Wall Award. In particular, section 10(12)(c) provides that a surveyor making an award may determine “ any other matter arising out of or incidental to the dispute………………….” Therefore, if in the opinion of the appointed surveyor, a Thames Build-Over Agreement is required, it will need to be included in the Party Wall Agreement. Icon Surveyors are happy to provide a free consultation to any building or adjoining owners who may be affected by the subject matter raised in this blog.

Note: This blog is not an authoritative interpretation of the law; it is intended as a general guide.

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Icon Surveyors

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