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Traditional house with a carefully designed rear extension

Building Control & Registered Building Control Approvers

Guidance on Building Control approval, inspections and Registered Building Control Approvers for house extensions.

Most house extensions need to comply with the Building Regulations, even where planning permission is not required.

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Planning permission considers whether an extension is acceptable in principle. The Building Regulations deal with the way the extension is designed and constructed, including structural safety, foundations, insulation, drainage, ventilation, fire safety and other technical matters.

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Before construction begins, you will normally need to decide who will provide the Building Control service for your project.

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For most domestic extension projects in England, homeowners can use either:

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  • the Building Control department at the local authority; or

  • a private-sector Registered Building Control Approver.

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Both routes are intended to help ensure that the work complies with the Building Regulations.

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What does Building Control do?

 

The Building Control body reviews the proposed work and carries out inspections as construction progresses.

The precise inspection stages will depend on the project, but an extension may require visits at key points such as:

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  • commencement of work;

  • excavation of foundations;

  • concrete foundations before they are covered;

  • ground-floor preparation and insulation;

  • drainage installations;

  • structural steelwork;

  • roof construction;

  • thermal insulation;

  • completion of the building work.

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It is important that the builder contacts the appointed Building Control body at the correct stages. Inspectors need to see certain elements before they are covered over.

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Once the work has been completed satisfactorily and the relevant inspections have taken place, a completion certificate can normally be issued.

What is a Registered Building Control Approver?

 

A Registered Building Control Approver is a private-sector organisation authorised to provide Building Control services in England.

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You may previously have heard these organisations described as Approved Inspectors. The terminology has changed following reforms to the building-control system. Private-sector Building Control organisations must now be registered with the Building Safety Regulator and are known as Registered Building Control Approvers.

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Homeowners may still come across the older term in conversations with builders, designers and other professionals. In practical terms, a Registered Building Control Approver provides the private-sector alternative to using the local authority Building Control department.

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Local authority or Registered Building Control Approver?

 

Both routes can be suitable for a house extension.

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A local authority Building Control team has knowledge of the local area and is often a straightforward choice for domestic projects.

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A Registered Building Control Approver may offer a more commercially focused service, particularly where a homeowner, builder or professional adviser already has an established working relationship with a particular provider.

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The best choice may depend on:

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  • the type and complexity of the extension;

  • the expected construction programme;

  • the level of technical support required;

  • inspection availability;

  • the geographical area;

  • the applicable fees;

  • the preferences of the homeowner and builder.

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The important point is to make the decision before work begins and ensure that the correct process is followed.

Building Regulations drawings and Building Control are different services

 

Homeowners sometimes assume that Building Control will prepare the technical drawings for an extension. That is not normally the case.

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Building Control reviews the proposed work and inspects construction for compliance. It does not usually design the extension or prepare the detailed drawing package for the builder.

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For most extension projects, it is sensible to obtain a proper set of Building Regulations drawings before construction begins. Depending on the project, these may include:

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  • detailed floor plans and elevations;

  • construction sections;

  • foundation details;

  • wall, floor and roof specifications;

  • insulation requirements;

  • drainage information;

  • ventilation details;

  • fire-safety provisions;

  • structural information and steelwork details;

  • notes to assist the builder and Building Control inspector.

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Structural calculations may also be required where the work includes steel beams, load-bearing wall removals, unusual foundations or other structural alterations.

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Why technical drawings matter

 

A planning drawing package may be enough to explain the appearance and general layout of an extension, but it is not usually sufficient for construction.

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Building Regulations drawings provide a clearer technical basis for the project. They help:

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  • Building Control review the proposed work;

  • structural engineers coordinate their calculations;

  • builders prepare more reliable quotations;

  • homeowners compare quotations on a more consistent basis;

  • trades understand what is expected;

  • reduce avoidable misunderstandings during construction.

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Trying to build an extension from planning drawings alone can lead to missing information, inconsistent quotations and expensive decisions being made on site.

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Full Plans applications and Building Notices

 

There are different ways to approach Building Regulations approval.

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For many extension projects, a Full Plans application is the more suitable route. Detailed drawings, specifications and supporting information are submitted for review before the work progresses too far. This can help identify technical issues at an earlier stage.

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A Building Notice may be available for certain domestic works. This is a less detailed route and may be appropriate for some smaller or relatively straightforward projects. However, it places more responsibility on the homeowner and builder because the work proceeds without the same level of detailed plans approval in advance.

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For a substantial house extension, particularly where structural work is involved, preparing a proper technical drawing package is generally the safer approach.

When should you appoint Building Control?


Building Control should be considered before construction begins.
 

A sensible sequence for many extension projects is:
 

  1. Finalise the proposed layout.

  2. Obtain planning permission or confirm the relevant permitted development position.

  3. Prepare the Building Regulations drawings.

  4. Obtain structural calculations where required.

  5. Select a local authority Building Control service or Registered Building Control Approver.

  6. Submit the relevant information.

  7. Agree the inspection process.

  8. Begin construction once the appropriate arrangements are in place.
     

Early preparation gives the builder a clearer basis for pricing and reduces the likelihood of technical issues being discovered after work has already started.

 

What happens if work has already started?


Do not ignore the issue if building work has begun without the correct arrangements.
 

The available options will depend on the circumstances, the stage reached and whether important construction details remain visible for inspection.
 

You may need advice from a Building Control body and suitably experienced professionals. In some cases, elements may need to be exposed or additional information may be requested before compliance can be established.
 

It is usually easier and less expensive to put the correct arrangements in place before construction begins.

 

Other professionals you may need


Building Control is only one part of the wider extension process.
 

Depending on your project, you may also need:
 

  • architectural design and planning support;

  • Building Regulations drawings;

  • structural engineering;

  • party wall advice;

  • an extension builder;

  • project management;

  • glazing, rooflight and door specialists;

  • drainage or groundworks contractors.
     

Good coordination between the design team, structural engineer, Building Control body and builder can make the construction stage considerably smoother.

 

Find Building Control and technical support through APN


The Architectural Partner Network has been developed by practising residential design and planning professionals with over 40 years of experience in home improvement projects across London and the Home Counties.
 

APN is not a generic mass lead-selling website. The aim is to help homeowners understand the services they may need and connect them with relevant professionals where appropriate.
 

Tell us about your extension, the stage you have reached and the type of support you require. Where suitable professionals are available, your details can be shared with selected APN partners who may be able to assist.

 

Tell us about your extension


Whether you are preparing your technical drawings, choosing a Building Control provider or looking for assistance with a project that is already underway, complete our short enquiry form and tell us what you need.

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