Building Regulations London: A Complete Guide for Homeowners

Building Regulations are legal standards set by the government (the Building Regulations 2010, as amended) that apply to building work in England. They are enforced by Building Control bodies — either the Local Authority Building Control (LABC) at your council, or a private Approved Inspector.

The Regulations are divided into Approved Documents — each covering a different aspect of the build:

• •**Part A — Structure**: the building must be structurally stable under all foreseeable loads
• •**Part B — Fire Safety**: the building must resist the spread of fire and provide safe escape
• •**Part C — Site preparation and resistance to moisture**: damp prevention
• •**Part E — Sound**: resistance to the passage of sound between dwellings
• •**Part F — Ventilation**: adequate fresh air supply and extraction
• •**Part G — Sanitation, hot water safety and water efficiency**: bathroom and kitchen requirements
• •**Part H — Drainage and waste disposal**: drainage design
• •**Part J — Combustion appliances**: boilers, stoves, flues
• •**Part K — Protection from falling**: stairs, balustrades, guarding
• •**Part L — Conservation of fuel and power**: thermal performance and energy efficiency
• •**Part M — Access to and use of buildings**: accessibility requirements
• •**Part O — Overheating**: residential buildings must not overheat (new since 2022)
• •**Part P — Electrical safety**: electrical installation in dwellings
• •**Part Q — Security**: windows and doors in new dwellings
• •**Part S — Infrastructure for charging electric vehicles**: new from 2023

For most residential extension and conversion projects, the Approved Documents most relevant are: Part A (structure), Part B (fire safety), Part F (ventilation), Part L (thermal performance), and Part P (electrics).

You need Building Regulations approval for most building work. The list of exempt works is narrower than many homeowners realise.

• **Works that ALWAYS require Building Regulations approval**:
• •All extensions and conversions
• •Loft conversions
• •New structural openings (removing load-bearing walls, new doors/windows in load-bearing walls)
• •Garage conversions to habitable rooms
• •New drainage or changes to drainage systems
• •Electrical work (certain types — see Part P below)
• •New boilers and heating system changes
• •Re-roofing where the thermal performance of the roof changes
• •Change of use of a building
• •New buildings

• **Works that do NOT require Building Regulations approval** (generally):
• •Most repairs and maintenance (like-for-like replacement)
• •Internal decoration
• •Garden paths, drives, and patios
• •Small garden structures (under certain size limits)
• •Replacement windows that are installed by a FENSA-registered installer (they self-certify compliance)

**Part P (electrical work)**: all new electrical circuits in a home require either a qualified electrician who is registered with a competent person scheme (such as NICEIC, NAPIT, or SELECT) — who self-certifies — or a Building Control application. In practice, hire a registered electrician; they handle their own certification.

**The key rule**: when in doubt, check with your local Building Control authority. A call or email to the council's Building Control team is free and will confirm whether approval is needed. Operating without required Building Regulations approval is a criminal offence, and the work can be required to be opened up or demolished.

There are two routes to Building Regulations approval in England:

• **Full Plans Application**:
• •Submit detailed drawings and specifications before work starts
• •Building Control reviews the plans and issues a conditional or unconditional approval
• •Work can proceed to the approved plans
• •Building Control inspects at key stages (foundation, DPC, structure, insulation, drainage, completion)
• •On completion, a Completion Certificate is issued

Advantages: certainty before starting; the contractor knows exactly what is required; approval is in writing; lenders and solicitors prefer this route.

Disadvantage: slower to start (approval can take 5 weeks).

• **Building Notice**:
• •No drawings or specifications submitted in advance
• •Work starts immediately (48 hours notice to Building Control required)
• •Building Control inspects at key stages and advises
• •If the work does not comply, Building Control can require it to be redone
• •A Completion Certificate is issued at the end if compliant

Advantages: faster start.

Disadvantages: no advance certainty; Building Control can require changes mid-build which costs more than if they had been designed correctly from the start; not suitable for complex or structural work.

**Which route is recommended?** For any project involving structural work, loft conversions, basement conversions, or extensions: Full Plans is strongly recommended. The cost of Getting the design right in advance is much less than the cost of correcting it mid-build.

For simple works (like-for-like bathroom replacement, small partition wall): a Building Notice may be acceptable.

**Approved Inspector route**: instead of the council's LABC, you can use a private Approved Inspector. They operate under a different statutory framework (since the Building Safety Act 2022, they are now called Registered Building Inspectors under the new scheme). Private inspectors are often faster than the council for approvals.

• **Building Regulations fees (LABC, London, 2026)**:
• Fees vary by council and project type, but approximate ranges:
• •Small extension (under 40m²): £300–£700
• •Extension 40–100m²: £600–£1,200
• •Loft conversion: £400–£900
• •Full house refurbishment: £600–£1,400

The Building Regulations Completion Certificate is the most important document from the building control process. It is your written evidence that the works were carried out in compliance with Building Regulations and inspected by a qualified authority.

**Why the Completion Certificate is critical**:

1. **Property sale**: when you sell your property, your solicitor will be asked by the buyer's solicitor to produce all relevant permissions and certificates for works carried out. Any building work without a Completion Certificate — including works done by previous owners — will be flagged. Buyers and their mortgage lenders may require a retrospective inspection, an indemnity insurance policy, or may reduce their offer to reflect the unknown risk.

2. **Remortgage**: lenders increasingly require documentary evidence that building works comply with Building Regulations. A new mortgage survey may flag uncertified works.

3. **Insurance**: if a structural failure occurs and the work was done without Building Regulations approval, your home insurer may decline the claim.

4. **Safety**: the Completion Certificate is confirmation that the work was inspected by a qualified professional and meets the legal safety standards — structural, fire, and electrical.

• **What if previous owners did work without Building Regulations?**
• This is a common discovery on older London properties. Options:
• •**Regularisation Certificate**: apply to the council for retrospective Building Regulations approval. Building Control inspects the work (which may require opening up walls or floors to inspect hidden elements). If compliant, a Regularisation Certificate is issued. If not, remedial work is required.
• •**Indemnity insurance**: a one-off insurance policy that covers the risk of the council requiring the works to be redone. This is the most common route when the works are old (10+ years), the original contractor cannot be traced, and the work appears to be compliant. Indemnity insurance does not confirm the work is safe — it only covers the financial risk of enforcement action.

**rcbGroup practice**: we apply for Building Regulations on all applicable projects, manage all inspections as part of our service, and ensure every client receives their Completion Certificate before we consider the project closed.

**Can I do building work without Building Regulations?** For most building work, no. Operating without required approval is a criminal offence under the Building Act 1984 (to be replaced by the Building Safety Act 2022 regime as it rolls out). The council can serve an enforcement notice requiring the works to be corrected or demolished within 12 months of completion. After 12 months, they cannot enforce the regulations but the lack of approval will still affect your sale.

**Do I need Planning Permission AND Building Regulations?** Yes — these are separate systems. Planning permission controls what you build. Building Regulations control how you build. You can have planning permission but still fail Building Regulations (if the design doesn't meet the technical standards), and you can have works that are Permitted Development (no planning needed) but still require Building Regulations.

**Does replacement of like-for-like windows need Building Regulations?** Not if the installer is FENSA-registered — they self-certify compliance with Part L (thermal performance) and Part K (safety glazing). If you are enlarging a window opening in a load-bearing wall, structural work is involved and Building Regulations apply.

**What is a Regularisation Certificate?** A Regularisation Certificate is retrospective Building Regulations approval for work done without approval. The application is made to the local council. An inspector examines the work (often requires opening up). If compliant, the certificate is issued. If not, you must make the work compliant before the certificate can be issued.

**Does an extension with Permitted Development need Building Regulations?** Yes — Permitted Development only exempts you from planning permission. Building Regulations still apply. Every extension, regardless of how it is approved (Permitted Development, Prior Approval, or Full Planning Permission), must comply with Building Regulations and must be inspected by Building Control.