A property owner discovered that an extension had been constructed over a Thames Water sewer without a build over agreement. Thames Water had reportedly told the builder that an application was required before work began, but the builder proceeded without making one.
The problem went further. The original manhole above the sewer had apparently been removed and replaced with a smaller plastic inspection chamber. The owner was left asking whether retrospective approval could be obtained, whether a completion certificate could be issued and, ultimately, whether the flat could still be sold.
This is a useful example of how a functioning extension can conceal a legal and practical problem. The building may look complete and the drains may work, but neither fact establishes that the water company consented to construction over its sewer.
Did you discover a missing build over agreement when selling or remortgaging?
The drainage search, title documents, building records and original conveyancing file may help establish what was known when you bought and what advice you received.
Read the When I Bought missing service rights and build over agreement guide
What is a build over agreement?
A build over agreement is an agreement with the relevant sewerage undertaker permitting construction over or close to a public sewer or lateral drain.
The purpose is not merely administrative. A public sewer must remain structurally protected and, where necessary, accessible for inspection, maintenance and repair.
Thames Water describes a build over agreement as a contract required when building over or near one of its sewers. Its published requirements depend on matters including the type and location of the sewer and the nature of the proposed work.
Anyone planning work should therefore check the current requirements of the relevant water company before construction begins. The requirements are not necessarily identical across every undertaker or every sewer.
The builder reportedly knew an application was required
The unusual feature of this case is that Thames Water had apparently contacted the builder before the work commenced and explained that a full application was required.
The builder nevertheless proceeded without obtaining the agreement.
That makes this different from a case where an owner only discovers years later that a sewer was present or that a previously private pipe had subsequently become a public sewer. Here, the need to address the sewer appears to have been raised before construction.
If the builder was contractually responsible for securing the necessary approvals, the correspondence with Thames Water and the terms of the building contract may become important. The owner may need advice on whether the builder remains responsible for the cost of investigation, remedial work or a retrospective application.
Why does removing the manhole matter?
A manhole or inspection chamber can provide access to the drainage system for investigation, clearing blockages, maintenance and repair.
Replacing an existing manhole with a smaller chamber may affect whether suitable access remains available. That could influence whether the water company is prepared to approve the arrangement retrospectively.
The important questions include:
- the status and ownership of the sewer;
- the sewer’s route and depth;
- the position of the extension in relation to it;
- the structural design and foundations;
- whether the sewer remains accessible;
- whether the replacement chamber is adequate;
- whether the work risks damage to the sewer; and
- whether diversion or remedial construction is required.
The fact that the sewer currently functions does not answer those questions. A water company will be concerned with continued access, structural integrity and the ability to deal with a future failure.
Planning permission is not a build over agreement
Several different regulatory and consent regimes can apply to the same extension. They should not be treated as interchangeable.
Planning permission concerns whether development is permitted under planning law. Building regulations concern standards applicable to the construction. A build over agreement concerns construction over or close to the sewerage undertaker’s infrastructure.
Water UK’s guidance explains that planning permission, permitted development rights or building regulations approval do not automatically provide consent to build over or close to a water company’s sewer.
It is therefore possible for an extension to have planning permission while lacking build over consent. It may also have some building control documentation without establishing that the water company approved the sewer arrangement.
Can a completion certificate still be issued?
The position should not be reduced to a universal rule that no completion certificate can ever be issued without a build over agreement.
The answer may depend on:
- the building control route used;
- the stage reached before the issue was identified;
- what inspections were undertaken;
- the applicable building regulations requirements;
- whether the sewer was public at the relevant time;
- the evidence available about the foundations and drainage; and
- whether the water company’s requirements remain unresolved.
The owner should ask the building control body to identify precisely what prevents certification and what evidence or remedial work would be required.
A missing completion certificate and a missing build over agreement are related but separate matters. Resolving one does not necessarily resolve the other.
Our earlier article on missing building regulations paperwork when selling or remortgaging explains why the first task is to establish whether approval was never obtained or whether the relevant document has simply been lost.
Can retrospective approval be obtained?
A retrospective application may be possible, but approval should not be assumed. The water company will need sufficient information to assess the work and its effect on the sewer.
The owner may be asked to provide:
- plans showing the property, extension and sewer;
- details of the foundations;
- drainage drawings;
- information about the sewer’s condition;
- evidence of construction methods;
- access arrangements; and
- details of the altered inspection chamber.
Where the work does not satisfy the relevant requirements, the water company may require alterations, improved access or another form of remediation before it is willing to approve the arrangement.
The most serious concern would be a requirement to remove or substantially alter part of the extension. Whether that risk exists depends on the actual sewer and construction, not merely on the absence of a document.
Could indemnity insurance solve the problem?
Indemnity insurance is sometimes proposed where a build over agreement cannot be produced. It should not be treated as equivalent to retrospective consent.
A policy may cover defined financial consequences if enforcement occurs. It does not:
- grant retrospective build over approval;
- confirm that the extension is structurally sound;
- confirm that the sewer has not been damaged;
- provide physical access to the sewer;
- prevent the water company exercising rights outside the policy cover; or
- guarantee that every mortgage lender will accept the property.
The policy conditions must be checked carefully. Contacting the water company before considering insurance can affect whether cover remains available. In this case, however, Thames Water had reportedly already communicated with the builder, so the possibility of insurance would need particularly careful investigation.
The seller should not purchase a policy before the buyer’s conveyancer and lender have confirmed what problem the policy is expected to address and whether it will be accepted.
Can the flat still be sold?
A missing build over agreement does not automatically make a property impossible to sell. It can, however, narrow the available solutions and create delay.
A buyer and mortgage lender may want to know:
- whether the sewer is public;
- whether consent was required when the extension was built;
- whether any applicable self certification or protocol applied;
- whether retrospective approval is available;
- whether building control documentation exists;
- whether sewer access has been obstructed;
- whether remedial work is required; and
- whether an acceptable indemnity policy can be obtained.
A cash buyer may take a different view from a buyer dependent on mortgage finance, but the physical and legal risks do not disappear merely because no lender is involved.
Marketability also extends beyond the immediate transaction. A buyer may reasonably ask whether the same problem will arise again when the property is later sold or remortgaged.
What if the owner bought the property with the extension already present?
If the extension had already been constructed when the present owner purchased the property, the original conveyancing file becomes particularly important.
The drainage and water search may have identified a public sewer within the property boundary. The property information forms may have disclosed the extension and the approvals available. The survey may also have identified the location or age of the work.
The relevant questions include:
- Did the drainage search reveal the sewer?
- Was the extension shown on the title plan, search plan or survey?
- Was a build over agreement requested from the seller?
- Was its absence reported to the buyer?
- Was Thames Water contacted before an insurance option was considered?
- Was an indemnity policy obtained?
- Did the original mortgage lender have to be notified?
- Was the buyer warned about future sale and remortgage difficulties?
The When I Bought missing service rights page specifically addresses extensions or conservatories built over or close to public sewers where water company consent cannot be produced.
Why the original lender and purchase date matter
A mortgage completing when the property was purchased does not establish that every lender would have accepted the missing agreement. Nor does it show what information was supplied to the original lender.
Mortgage lender requirements can differ and can change over time. The relevant historical question is what the particular lender required on the date of the original transaction.
The Lexsure Lender Archive records concerning missing easements and service rights can help establish the recorded lender specific requirements applying at the relevant time.
Historical lender requirements are only part of the evidence. The original search, title documents, enquiries, survey, Report on Title and communications with the lender must also be considered.
Missing consent and missing service rights are connected
A build over problem is not limited to a missing certificate. It concerns the legal and practical relationship between the building and the sewer beneath it.
The property may be affected by rights allowing the water company to retain, inspect, maintain and repair its infrastructure. Those rights may restrict what the owner can build and may permit access when works are required.
For conveyancers reporting on related title defects, the Report on Title paragraph concerning the absence of an easement illustrates why the existence, use and repair of property services must be considered expressly.
Our earlier article, Missing Service Rights: Why Working Pipes Can Still Hold Up Your Property Sale, explains why a physically functioning service does not necessarily establish that the necessary legal rights exist.
What should the owner do next?
The owner should obtain coordinated advice before contacting additional parties or committing to a particular solution.
The practical investigation may include:
- obtaining the drainage and water search;
- confirming whether the relevant pipe is a public sewer or lateral drain;
- obtaining the plans and construction records for the extension;
- reviewing the correspondence sent by Thames Water before construction;
- establishing what the builder agreed to do;
- asking the building control body what remains outstanding;
- obtaining technical advice about the foundations, sewer and inspection chamber;
- asking Thames Water about the appropriate application route where advised to do so;
- checking whether insurance remains available and useful; and
- reviewing the mortgage lender’s requirements before selecting a solution.
If the property was bought with the extension already in place, the owner should also obtain the original purchase file and Report on Title.
Did the missing build over agreement only emerge when you tried to sell or remortgage?
If the extension existed when you bought, the original drainage search, conveyancing enquiries and lender requirements may help establish whether the problem should have been identified and explained.
The sewer was there before the sale
The absence of a build over agreement may first become urgent when a buyer’s conveyancer raises it, but the underlying facts are usually older. The sewer was already present. The extension had already been constructed. The missing consent did not originate with the sale.
The current priority is to determine whether the work can be approved, insured or altered so that the transaction can proceed.
If the owner purchased the property with the extension already in place, there is a second question: what did the available information show, what enquiries were made and what was the buyer told before completion?
This article provides general information and is not legal advice. Build over requirements vary according to the water company, the status and position of the sewer, the date and nature of the work and the facts of the particular property.