Building Regulations in London: A Plain-Language Homeowner Guide

Many homeowners conflate Building Regulations and planning permission. They are entirely different systems with different purposes:

**Planning permission** controls whether you can build at all — it considers the impact of development on the local area (appearance, use, scale, neighbours). It is granted or refused by the Local Planning Authority (LPA).

**Building Regulations** control HOW you build — the standards of construction must meet in terms of structure, fire safety, energy efficiency, ventilation, drainage, accessibility, and similar technical requirements. They are enforced by Building Control, which may be the local authority's Building Control department or an approved inspector (private sector).

The key difference in practice: - A project may need planning permission but no Building Regulations approval (e.g. a change of use of an existing building without structural works) - A project may need Building Regulations approval but no planning permission (e.g. most loft conversions under Permitted Development) - Most significant construction projects need both - Some simple projects need neither

Never assume that because you have planning permission, Building Regulations are also satisfied — they are obtained through completely separate processes.

Building Regulations apply to most new construction work, extensions, and significant alterations in England. They do not apply to routine repairs and like-for-like maintenance.

**Work that typically requires Building Regulations approval**: - New extensions or outbuildings over 30m2 in floor area (extensions under 30m2 have some exemptions but often still need approval for structural, drainage, or fire-separation reasons) - Loft conversions - Conversion of a garage to habitable accommodation - Structural alterations (removing or opening load-bearing walls) - Installing or replacing a boiler or heating system - New or altered electrical circuits (Part P) - Creating new rooms in a basement - Building a new dwelling (including through subdivision or conversion) - Any works to a listed building that affect the character of the building

**Work that typically does NOT require Building Regulations approval**: - Replacing windows like-for-like (but must be double-glazed and must meet energy requirements; FENSA/CERTASS certification provides compliance evidence) - Repointing brickwork - Plastering or redecorating - Installing kitchen units (unless creating new drainage connections) - Replacing floor coverings - Internal non-structural partition walls (if no fire separation implications) - Small porches under 30m2 that are not heated - Small conservatories under 30m2 with a separation door and roof at least 75% translucent

If in doubt, contact your local Building Control department for advice before starting work — they will advise whether approval is needed.

The Building Regulations are organised into Parts (A to T). For typical London residential projects, the most relevant Parts are:

**Part A — Structure**: Requires that buildings are structurally stable and robust. Applies to all structural work — foundations, beams, walls, floors, roofs. A structural engineer's design demonstrating compliance is normally required for structural alterations.

**Part B — Fire Safety**: Requires adequate means of escape, fire spread limitations, and fire detection. Particularly relevant for loft conversions (where escape from the new loft room must be designed), HMO conversions, and any works affecting fire compartmentation between dwellings.

**Part C — Site Preparation and Resistance to Contaminants and Moisture**: Requires damp-proof courses, appropriate ground conditions, and resistance to moisture. Relevant to extensions (DPC continuity) and basement conversions (waterproofing).

**Part F — Ventilation**: Requires adequate ventilation to habitable rooms, bathrooms, and kitchens. Particularly relevant when rooms are made more airtight (e.g. after window replacement or insulation). Mechanical extract ventilation (MEV) or heat recovery ventilation (MVHR) may be required.

**Part L — Conservation of Fuel and Power**: Sets standards for energy efficiency — U-values for walls, roofs, floors, windows, and doors. For extensions, Part L1A (new dwellings) and Part L1B (existing dwellings) apply. Current minimum U-values for extensions: walls 0.18 W/m²K, roof 0.15 W/m²K, floor 0.18 W/m²K, windows 1.4 W/m²K.

**Part M — Access to and Use of Buildings**: Requires accessible design for new dwellings and some material changes of use. Includes requirements for accessible WCs, step-free entrances, and doorway widths in new builds.

**Part P — Electrical Safety**: Requires that electrical installation work in dwellings is designed and installed to BS 7671. Notifiable work (new circuits, consumer unit changes, work in kitchens and bathrooms) must be certified either by a registered competent person (e.g. NICEIC/NAPIT registered electrician) or by Building Control.

There are two routes to Building Regulations approval:

**Full Plans (Formal Application)** You (or your designer/contractor) submit a full set of drawings and structural calculations to Building Control before work starts. Building Control reviews the submission and issues an approval (possibly with conditions or requests for more information). Inspections are then carried out at key stages during construction.

Advantages: You have an approved design before starting — reduces the risk of being asked to change work on site. Required for complex projects.

**Building Notice** You notify Building Control before starting work, but do not submit drawings upfront. Building Control then visits the site at key stages and inspects work as it progresses. If work does not comply, you may be asked to open up or change it.

Advantages: Faster to start work. Disadvantages: Risk of non-compliance being discovered on site; not suitable for complex structural or drainage works; cannot use this route if depositing plans for a mortgaged property.

**Completion Certificate** At the end of the project, after a satisfactory final inspection, Building Control issues a Completion Certificate. This document is the formal record that the works were inspected and found to comply. It is required when the property is sold.

**Choosing Between Local Authority Building Control (LABC) and Approved Inspectors (AI)** Approved Inspectors are private-sector Building Control companies. They often offer faster turnaround and a more service-focused approach. The fee structures differ — get quotes from both if cost or speed is a concern.

Building Regulations fees vary by work type and local authority. Typical fees for common London residential projects:

- **Small extension (up to 40m2)**: £400–£800 application fee - **Extension 40–100m2**: £700–£1,500 application fee - **Loft conversion**: £600–£1,200 application fee - **Structural alterations (single beam)**: £300–£600 application fee - **New dwelling or major conversion**: £1,200–£2,500+ application fee

These are council fees and are subject to VAT. Approved Inspector fees are negotiated and may differ from council fees.

Note that the Building Regulations application fee is separate from your professional fees (structural engineer, architect) and contractor costs.