Building regulations, explained.
What they cover, how approval works, and the other permissions that often go alongside: party wall notices, build over agreements and structural calculations.
Planning says where. Building regulations say how.
Our planning permission guide covers the first. This guide covers the second.
Planning permission decides whether a building is acceptable in that place. Building regulations set the technical standards for how it is built, for the safety, health and energy performance of the people who use it.
They are separate applications with separate fees, and they are assessed by different people. Almost every extension, loft conversion and garage conversion needs building regulations approval, even when planning permission is not required. That includes projects built under permitted development.
Three ways to get approval.
You can use your council’s building control team or a private approved inspector. Private inspectors are now registered with the Building Safety Regulator and apply the same standards. Either way, the route comes down to three options.
Full plans
Detailed drawings, a specification and any structural calculations are checked before work starts, and you receive a decision. It is the safest route, and the one we recommend for anything beyond a simple job.
Building notice
You tell the council you are about to start, with no drawings approved beforehand. It suits small domestic work, but problems found on site can mean expensive changes, and lenders and buyers often prefer full plans.
Regularisation
For work already carried out without approval. The council inspects it, may ask you to open it up, and can issue a certificate if it complies.
How approval works.
A typical full plans application follows five steps.
Design to the regulations
We prepare detailed drawings and a specification showing the structure, insulation, drainage, fire safety and ventilation. Structural calculations from an engineer are included where they are needed.
Submit the application
The application goes to your chosen building control body with the plans, calculations and fee. We check at this stage whether a public sewer or drain runs close to your extension.
Approval
The building control body checks the plans and either approves them, approves with conditions, or asks for changes. For a full plans application this is due within five weeks, or two months if agreed.
Notify and inspect
You or your builder notify building control at set stages, typically before work starts, at foundations, damp proofing, drains, structure and insulation before they are covered, and at completion. The inspector visits and checks each one.
Completion certificate
When the work is finished and satisfactory you receive a completion certificate. Keep it safe, because a buyer’s solicitor will ask for it. Keep any electrical, gas and window certificates with it.
What building control checks.
The rules are set out in a series of Approved Documents, each lettered. These are the parts that matter most for home extensions and loft conversions.
Structure
Foundations, walls, floors, roofs and beams, including openings in load-bearing walls.
Fire safety
Escape routes, smoke alarms, fire doors and, in loft conversions, escape windows and protected stairs.
Ground and moisture
Protection from damp, ground contamination and radon, including damp proof membranes.
Ventilation
Extract fans, trickle vents and purge ventilation in kitchens, bathrooms and habitable rooms.
Drainage
Foul and surface water drainage, and where new work affects existing drains.
Heating appliances
Flues, chimneys and the air supply for stoves, fires and boilers.
Stairs and glazing safety
Stair dimensions, guarding, and safety glass in doors and low windows.
Energy
Insulation, glazing performance and limits, heating and lighting efficiency for new work.
Electrical safety
New electrical work must be designed, installed and certified by a competent person.
When you need a structural engineer.
Building control will not approve structural work without calculations. An engineer designs it and signs it off.
A structural engineer works out the size of the steel beams, the foundations and any other load-bearing elements, then provides calculations and drawings for building control and your builder. The work is usually required when you are:
- Removing or opening up a load-bearing wall or chimney breast, which needs a beam to carry the load.
- Adding new foundations, or building near trees or on clay soils where ground movement is a concern.
- Converting a loft, which usually needs new floor beams and a supported dormer or roof structure.
- Forming large openings such as bi-fold or sliding doors.
- Adding a storey or building a basement.
The calculations are normally submitted with the building regulations application. The engineer may also inspect on site, particularly for steelwork and foundations. We prepare the architectural drawings and work alongside your engineer so the two sets agree.
Telling your neighbours the right way.
The Party Wall etc. Act 1996 is a separate legal process. It is not part of planning or building regulations, and the council does not manage it.
If your work affects a wall shared with a neighbour, builds on or against the boundary, or involves digging close to their building, you must serve notice on them before you start.
| Type of work | Notice | Examples |
|---|---|---|
| Building at the boundary | 1 month | A new wall built up to or astride the boundary. |
| Work to a party wall | 2 months | Cutting in beams, raising or underpinning a shared wall, or work to a shared chimney breast. |
| Excavation near a neighbour | 1 month | Digging within 3 metres of their building below their foundations, or within 6 metres if it meets a 45 degree line from the bottom of their foundations. |
Your neighbour can consent in writing, or dissent, in which case a surveyor is appointed to set out the terms in a binding document called an award. If they do not reply within 14 days, a dispute is treated as having arisen. A notice is valid for a year, so the work must begin within that time.
Even if your neighbours are friendly, you should still serve notice and get their written consent. When the work is for your benefit, you normally pay the reasonable costs of the surveyors, including your neighbour’s.
Worth knowing
- Notices should be served well before work starts. Missing the notice period can delay the build.
- A schedule of condition of your neighbour’s property before work starts protects both of you.
- Party wall matters can arise even with an extension entirely on your own land, if the foundations are deep or close to the boundary.
Build over agreements.
If a public sewer or drain runs under or close to your extension, the water company must agree to the work.
Since 2011 most shared drains and sewers that were once private now belong to the water company. Many of them run through back gardens, which is exactly where extensions go. Building over or close to one, usually within three metres and sometimes more depending on the pipe size, needs the water company’s approval.
In most of Warwickshire the water company is Severn Trent Water. Other areas have different companies, such as Thames Water or Anglian Water.
- Check early. The water company’s sewer maps show many public sewers, but older ones and those adopted in 2011 do not always appear, so a sewer can turn up once work has started.
- A simple declaration or a formal agreement. For a small domestic extension with pipes up to 150mm and no manholes to move, Severn Trent allows a self-certification form. Larger pipes, manholes, raft or piled foundations, or a sewer with an easement need a formal build over agreement.
- A CCTV survey of the drain before and after the work is often required.
- Timing. Severn Trent aims to decide within 10 working days of a complete application and payment. A refusal may mean redesigning the foundations, or diverting the pipe.
Your building control body will check the sewer maps when you apply and tell you if a sewer is close. It is far cheaper to find out at the design stage than after the foundations are dug.
Certificates to collect.
Alongside the completion certificate, keep the documents your installers give you. A buyer, lender or insurer may ask for any of them.
Electrical certificate
From a registered electrician for any new or altered circuits.
Gas Safe certificate
For new or moved boilers, gas fires and pipework.
Window certificate
From the installer, for new windows and doors fitted under a competent person scheme.
Common questions.
Do I need building regulations for permitted development?
Yes. Permitted development only deals with planning. Most extensions and loft conversions also need building regulations approval.
Council or private approver?
Both are valid and apply the same regulations. You choose. A private approver can sometimes be quicker or more flexible on timing, while the council may be cheaper. We can talk you through the choice.
How much does approval cost?
Fees are set by the building control body and depend on the type and size of the work, so ask for a quote. They are separate from planning fees and from any engineer’s fees. If the application is made through the Planning Portal, a service charge can apply on top of the building control fee, so we confirm the total before we submit.
Does a loft conversion need an engineer?
Almost always. The existing ceiling joists are not designed to carry a floor, so new beams and a structural design are normally needed.
What if work was done without approval?
You can apply for regularisation, which allows the council to inspect the work and, if it complies, issue a certificate. They can also require work to be opened up or altered. Without a certificate it can cause problems when you sell.
Who is responsible for compliance?
The person carrying out the work and the owner are both responsible. Make sure your builder knows which stages building control must inspect, and keep the paperwork.
Do I need a party wall notice if my neighbours are happy?
Yes, you should still serve notice, so they can consent in writing. It is a legal requirement, and it protects both of you.
Does this apply in Wales and Scotland?
No. Building regulations are devolved, and the rules differ. This guide covers England only.
Built right, first time.
We prepare the drawings and the building regulations application, and work alongside your structural engineer.
This guide is general information for England, reviewed October 2026, and is not professional advice for your property. Rules, fees and local practice change, so confirm the current position with your building control body, water company and a party wall surveyor where relevant. The rules in Wales, Scotland and Northern Ireland are different.