Building regulations drawings and construction details prepared for a London home project

Guide

Do I Need Building Regulations Approval in London? (2026)

Q: Do I need building regulations approval in London?

Almost certainly, for any building work beyond minor repairs. Extensions, loft and garage conversions, removing load-bearing walls, new drainage, replacement windows and new heating systems all typically need approval. It is separate from planning permission — most permitted-development work needs no planning application but still needs building regulations approval. Only narrow exemptions, such as small garden outbuildings, fall outside it.

Q: What is the difference between planning permission and building regulations?

Planning permission decides whether a development is acceptable in principle — its size, appearance and impact on the area. Building regulations decide whether the construction is safe and meets standards for structure, fire, energy, ventilation, drainage and access. They are separate approvals: most extensions and conversions need both, and satisfying one never satisfies the other.

Q: What is the difference between a full plans application and a building notice?

A full plans application submits detailed drawings for building control to approve before work starts, giving certainty on the design — the right route for structural or complex work. A building notice involves no prior approval and the work is simply inspected as it proceeds, which suits only very simple jobs and is risky for anything structural. For London extensions and conversions, full plans is almost always the sensible choice.

Q: Why do I need a building regulations completion certificate?

The completion certificate is issued after the final inspection and proves the work complied with the regulations. Buyers' solicitors ask for it whenever building work has been done, and a missing certificate is a common cause of delayed sales — sometimes forcing a costly retrospective regularisation years later. A clean completion certificate at the end is as important as the approval at the start.

Q: Can I use a private inspector instead of the council for building control?

For ordinary domestic work in London you can choose either the local authority's own building control team or a private building control approver (formerly called an approved inspector). Both carry out the same statutory function — approving the design and inspecting the work — and both can issue the completion certificate. Following the recent building-safety reforms, higher-risk buildings are handled by the Building Safety Regulator, but for a standard extension, loft or conversion the choice between council and private building control remains yours.

Q: What happens if work was done without building regulations approval?

Where past work never had approval and has no completion certificate, it can usually be put right through a regularisation application, which asks building control to inspect and certify existing work retrospectively — sometimes requiring parts to be opened up so they can be checked. It is far cheaper and less disruptive to get approval before building than to regularise afterwards, and unapproved work is a frequent cause of delay when a London home is sold, so it is worth resolving before marketing a property.

When a London home project needs building regulations approval — the difference from planning permission, full plans vs building notice, and why a completion certificate matters.

Building regulations are the half of the approval system that homeowners forget until building control turns up on site — or until a buyer's solicitor asks for the completion certificate years later. Unlike planning, which is about what a building looks like and how it affects its surroundings, building regulations are about safety and performance: structure, fire, insulation, ventilation, drainage and accessibility. Almost every extension, loft conversion, garage conversion or structural alteration in London needs building regulations approval whether or not it needs planning permission. This guide explains when approval is required, the two routes to get it, and why the paperwork at the end matters as much as the inspection.

The regulations are national, but they are enforced locally by each borough's building control department or an approved inspector. We prepare the technical drawings and construction details a full plans application needs so the work is signed off cleanly, before anything is commissioned, free.

Building regulations vs planning permission

The two systems answer different questions and are granted separately. Planning permission asks whether a development is acceptable in principle — its size, appearance and impact on neighbours and the area. Building regulations ask whether the construction is safe and meets minimum standards for structure, fire safety, energy efficiency, ventilation, drainage and access. A project can need planning permission but not building regulations (rare), building regulations but not planning permission (very common — most permitted-development work), or both (most extensions and conversions). Satisfying one never satisfies the other.

Planning — appearance, size, impact on the area
Building regs — structure, fire, energy, ventilation, drainage, access
Most permitted-development work still needs building regs
The two approvals are applied for and granted separately

What work needs building regulations approval?

Most building work beyond minor repairs needs approval. Extensions, loft and garage conversions, structural alterations such as removing a load-bearing wall, new or altered drainage, replacement windows, new heating systems and re-roofing all typically require it. A small number of things are exempt — many detached garden outbuildings under 15 square metres with no sleeping accommodation, some porches and conservatories below set sizes at ground level — but the exemptions are narrow and specific. If in doubt, the work almost certainly needs approval.

Extensions, loft conversions, garage conversions
Removing or altering load-bearing walls (structural)
New drainage, replacement windows, new heating systems
Narrow exemptions — small outbuildings, some porches/conservatories

Full plans vs building notice: the two routes

There are two ways to get building regulations approval. A full plans application submits detailed drawings and calculations to building control for approval before work starts, giving you a checked, approved design and certainty before you build — the right route for anything structural or complex. A building notice involves no prior approval: you notify building control and the work is inspected as it proceeds. It suits very simple jobs but carries real risk on anything structural, because a problem is only found once it is built. For extensions and conversions in London, the full plans route is almost always the sensible choice.

Full plans — drawings approved before you start (certainty)
Building notice — no prior approval, inspected as you build
Full plans is right for structural and complex work
Building notice suits only very simple projects

Who inspects the work — council or approved inspector?

Building control can be provided either by the local authority's own building control team or by a private approved inspector (registered as a building control approver), and you can choose. Either way, the inspector visits at key stages — foundations, damp-proofing, drainage, structure, insulation and completion — to confirm the work meets the regulations. Following recent reforms, higher-risk buildings fall under the Building Safety Regulator, but for ordinary domestic extensions and conversions the choice between local-authority and private building control remains.

Why the completion certificate matters

When the work passes its final inspection, building control issues a completion certificate (or final certificate). This document is the proof that the work complied with the regulations, and it is what a buyer's solicitor will ask for whenever building work has been done. Missing certificates are one of the most common causes of delayed or fallen-through sales, sometimes forcing a costly regularisation application years later to certify work retrospectively. Getting a clean completion certificate at the end is as important as the approval at the start — proper drawings make both straightforward.

How does building regulations approval actually work on a London project?

For most homeowners the process is more practical than the regulations make it sound. A full plans application turns the technical drawings and calculations into a checked, approved design before a builder is on site, and building control then inspects the work at defined stages as it is built. Understanding that rhythm — approval of the design, then a sequence of site inspections, then a completion certificate — makes it clear why the quality of the drawings at the start determines how smoothly the whole job signs off at the end. The regulations are national, but on the ground the experience is a working relationship between your drawings, your builder and the inspector.

What a full plans submission contains

A full plans application is more than pretty drawings. It sets out the construction in the detail building control needs to check compliance: foundation and structural design with supporting calculations, floor, wall and roof build-ups showing insulation to meet Part L, fire safety and escape provision, ventilation and drainage layouts, and the specific junctions where things like thermal bridging and weathering are resolved. On anything structural — removing a load-bearing wall, forming a large opening, a loft or an extension — a structural engineer's calculations sit alongside the drawings. Submitting this properly up front is what earns an approval you can build to without surprises.

The inspection stages on site

Once work starts, building control is notified at key points and visits to confirm the work matches the approved design and meets the regulations. Typical hold points are excavation and foundations before concrete is poured, damp-proof courses and oversite, drainage before it is covered, structural elements and steel beams, insulation, and a final completion inspection. Missing a notification — pouring foundations before they are seen, for instance — can mean opening work back up to prove it, so it is worth agreeing the inspection schedule with your builder at the outset. Passing the final inspection is what releases the completion certificate.

Building regulations drawings and construction detailing on a London desk, the technical set a full plans application submits for approval before work starts

Building regulations routes in London (2026)
Project	Building regs	Best route	Planning too?
Rear/side extension	Required	Full plans	Often (unless PD)
Loft or garage conversion	Required	Full plans	Sometimes
Removing a load-bearing wall	Required	Full plans	Usually not
Replacement windows	Required	Building notice / competent person	No
Small garden outbuilding (<15m²)	Often exempt	n/a	Usually PD

FAQ

Frequently asked questions

Do I need building regulations approval in London?+

Almost certainly, for any building work beyond minor repairs. Extensions, loft and garage conversions, removing load-bearing walls, new drainage, replacement windows and new heating systems all typically need approval. It is separate from planning permission — most permitted-development work needs no planning application but still needs building regulations approval. Only narrow exemptions, such as small garden outbuildings, fall outside it.

What is the difference between planning permission and building regulations?+

Planning permission decides whether a development is acceptable in principle — its size, appearance and impact on the area. Building regulations decide whether the construction is safe and meets standards for structure, fire, energy, ventilation, drainage and access. They are separate approvals: most extensions and conversions need both, and satisfying one never satisfies the other.

What is the difference between a full plans application and a building notice?+

A full plans application submits detailed drawings for building control to approve before work starts, giving certainty on the design — the right route for structural or complex work. A building notice involves no prior approval and the work is simply inspected as it proceeds, which suits only very simple jobs and is risky for anything structural. For London extensions and conversions, full plans is almost always the sensible choice.

Why do I need a building regulations completion certificate?+

The completion certificate is issued after the final inspection and proves the work complied with the regulations. Buyers' solicitors ask for it whenever building work has been done, and a missing certificate is a common cause of delayed sales — sometimes forcing a costly retrospective regularisation years later. A clean completion certificate at the end is as important as the approval at the start.

Can I use a private inspector instead of the council for building control?+

For ordinary domestic work in London you can choose either the local authority's own building control team or a private building control approver (formerly called an approved inspector). Both carry out the same statutory function — approving the design and inspecting the work — and both can issue the completion certificate. Following the recent building-safety reforms, higher-risk buildings are handled by the Building Safety Regulator, but for a standard extension, loft or conversion the choice between council and private building control remains yours.

What happens if work was done without building regulations approval?+

Where past work never had approval and has no completion certificate, it can usually be put right through a regularisation application, which asks building control to inspect and certify existing work retrospectively — sometimes requiring parts to be opened up so they can be checked. It is far cheaper and less disruptive to get approval before building than to regularise afterwards, and unapproved work is a frequent cause of delay when a London home is sold, so it is worth resolving before marketing a property.

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