Building Regulations Exemptions Guide London 2025: When You Don't Need Approval

**The legal basis for Building Regulations exemptions**:

The Building Regulations 2010 (SI 2010/2214) is the principal instrument regulating building work in England. Regulation 9 provides that the Building Regulations do not apply to work described in Schedule 2 of the Regulations. Schedule 2 is divided into Classes, each with its own conditions.

**Class 1 — Buildings controlled under other legislation**:

• Class 1 exempts certain buildings that are subject to their own specialist regulatory regime:
• •Buildings subject to the Explosives Act 1875 (e.g., licensed explosives stores)
• •Buildings subject to the Nuclear Installations Act 1965
• •Buildings subject to the Ancient Monuments and Archaeological Areas Act 1979 (Scheduled Ancient Monuments where works are authorised under a Scheduled Monument Consent)

*Practical relevance for London residential construction*: Class 1 is rarely relevant to domestic projects.

**Class 2 — Buildings not frequented by people**:

Class 2 exempts buildings into which people do not normally go, or only go intermittently for the purpose of inspecting or maintaining plant or machinery. The building must be a detached building at least 1m from the boundary of the site.

*Examples*: utility substations; plant rooms that are only accessed for maintenance.

*Practical relevance for London residential construction*: Class 2 is not relevant to most domestic projects — a garden room that people use regularly as an office or studio is NOT Class 2, regardless of how occasionally it might be used.

**Class 3 — Greenhouses and agricultural buildings**:

• Class 3 exempts:
• •**Greenhouses** — a greenhouse (a building used for growing plants) used for private purposes is exempt from Building Regulations, provided it is not used as a dwelling or for human habitation and is not attached to a dwelling (a greenhouse attached to the dwelling wall would require Building Regs for the connection to the dwelling)
• •**Agricultural buildings** — buildings used for agriculture (farming; horticulture) where people only enter the building occasionally for the purpose of maintenance

• *Greenhouse exemption conditions*:
• •The greenhouse must be used for growing plants — it must function as a greenhouse, not as a studio or office that happens to have glass walls
• •It must not be used as a dwelling or for habitation
• •It must be a free-standing building, not an extension of the dwelling
• •There is no specific size limit — large private greenhouses can be exempt from Building Regulations

*Practical relevance*: if you want to build a glass-roofed garden structure to use as a sitting room or home office, it is NOT a greenhouse under Class 3 — it requires Building Regulations approval. The Class 3 greenhouse exemption is based on use, not construction type.

**Class 4 — Temporary buildings**:

Class 4 exempts buildings intended to remain in position for less than 28 days. A contractor's site office; a scaffolding enclosure; a temporary event structure — provided the use is genuinely temporary and the structure will be removed within 28 days.

*Practical relevance*: not relevant to permanent domestic outbuildings or extensions.

**Class 5 — Ancillary buildings**:

Class 5 exempts buildings on a site in connection with a project being or to be carried out, intended to be removed when the project is complete. Site offices; welfare facilities; storage buildings used during construction — but only during the construction project, and only to be removed at completion.

*Practical relevance*: the contractor's site hut during an extension project is Class 5 exempt — but the extension itself, when complete, is not.

**Class 6 — Small detached buildings**:

• Class 6 is the most practically relevant exemption for London residential construction. It covers small detached buildings used as:
• •**Class 6(a)**: a detached single-storey building with a floor area not exceeding **30m²** which:
• - Contains no sleeping accommodation
• - Is either more than 1m from the boundary of the site, OR is constructed substantially of non-combustible materials
• - Has a floor area of 30m² or less

• •**Class 6(b)**: a detached single-storey building with a floor area not exceeding **15m²** which:
• - Contains no sleeping accommodation
• - No restriction on position relative to the boundary
• - Floor area ≤ 15m²

*Class 6 exemption in practice for common London scenarios*:

**Garden room (studio/office): ≤15m², no sleeping, free-standing** → **Exempt** under Class 6(b). No Building Regulations approval required.

**Garden room (studio/office): ≤30m², >1m from boundary, no sleeping, non-combustible materials (brick/block/concrete)** → **Exempt** under Class 6(a) if materials are non-combustible. A timber-frame garden room ≤30m² but not substantially non-combustible materials needs to be >1m from the boundary.

**Garden room (studio/office): ≤30m², within 1m of boundary, timber frame** → **NOT exempt** under Class 6(a). Requires Building Regulations approval because it is within 1m of the boundary and NOT substantially non-combustible materials.

**Garden room with sleeping accommodation (any size)** → **NOT exempt** under Class 6. Any garden room or outbuilding that contains sleeping accommodation (a bedroom; a bed-settee; a sofa bed used for sleeping) requires Building Regulations approval regardless of size or position.

**Timber-frame double garage: 30m²+** → **NOT exempt** under Class 6. Over 30m² takes it outside Class 6(a).

**Detached car port (open-sided; no walls)**: a car port with a roof but open on at least two sides and a floor area ≤30m² is typically exempt — but check the local Building Control position, as interpretation of 'detached building' versus 'roof structure attached to the dwelling' varies.

*The combustibility condition for Class 6(a) buildings near the boundary*:

'Substantially of non-combustible materials' in Class 6(a) means that the primary structure of the building — walls; roof; floor — is predominantly non-combustible. A brick-and-block cavity wall building with a concrete or mineral-wool flat roof and concrete floor: Class 6(a) exempt even within 1m of boundary. A timber-frame building with a GRP or felt roof: NOT substantially non-combustible — must be more than 1m from the boundary for Class 6(a) to apply.

*Why the boundary distance matters*: the Building Regulations concern for buildings within 1m of a boundary relates to fire safety — a building close to the boundary that catches fire can spread fire to neighbouring properties. The non-combustible materials condition addresses this risk. Buildings farther from the boundary have greater separation distance before fire can spread to a neighbouring property's structure.

**Class 7 — Extensions**:

Class 7 was removed from Schedule 2 by subsequent amendments — extensions to dwellings are not exempt from Building Regulations. All extensions to existing dwellings in England require Building Regulations approval (either full plans approval or building notice approval).

**The conservatory exemption — why it exists and when it applies**:

Conservatories are not directly mentioned in Schedule 2 of the Building Regulations 2010 — but they can be exempt from Building Regulations as a class of extension under a specific provision of Regulation 9 (not Schedule 2). Regulation 9(3) provides that an extension consisting of a conservatory, porch, covered yard, covered way, or carport (open on at least two sides) is exempt from the Building Regulations if:

• •**It is at ground level**
• •**The floor area does not exceed 30m²**
• •**The glazing and any fixed electrical installations comply with the applicable requirements of the Regulations** (i.e., glazing safety — Part K; electrical safety — Part P; energy efficiency — Part L applies to the conservatory's thermal separation from the dwelling)

• *The thermal separation requirement*: the most commonly misunderstood aspect of the conservatory exemption. For a conservatory to be exempt from Building Regulations, it must have an effective thermal separation between the conservatory and the rest of the dwelling. This means:
• •**The existing wall between the house and the conservatory must remain or be maintained** — the conservatory is thermally separated from the dwelling by the existing wall and door/window
• •**The separating wall between the house and the conservatory must have a door or window that can be closed** — to allow the conservatory to be 'separated' from the heated dwelling
• •**The heating system of the conservatory must be independently controllable** — if the conservatory is heated, its heating must be controllable separately from the main house heating system

If any of these conditions are not met — for example, if the separating wall is removed to create an open-plan kitchen-conservatory with no thermal separation — the conservatory exemption does NOT apply, and the whole extension requires Building Regulations approval.

*Floor area limit*: the 30m² floor area limit for the conservatory exemption is calculated as the floor area of the conservatory itself. A conservatory exceeding 30m² requires Building Regulations approval regardless of thermal separation.

*Practical consequence for kitchen extension vs. conservatory*: many clients want to open the kitchen into a rear glazed structure and treat it as a 'conservatory' to avoid Building Regulations. If the separating wall is removed (as is almost universally done for a functional kitchen-to-garden living space), the conservatory exemption is lost — the glazed extension becomes a full extension requiring Building Regulations approval for structure, insulation, drainage, electrical work, and all other relevant Parts.

**The porch exemption**:

• A porch is exempt from Building Regulations where:
• •It is at ground level
• •The floor area does not exceed 30m²
• •Glazing and electrical installations comply with Part K (glazing safety) and Part P (electrical safety)
• •The door or window between the porch and the dwelling is maintained (thermal separation)

A porch is a modest entrance vestibule — the exemption is designed for small entrance porch additions, not large additions to the front of the dwelling.

**Class 6 detail — what 'no sleeping accommodation' actually means in practice**:

The Class 6 exemption excludes any outbuilding that 'contains sleeping accommodation'. In practice:

• •A garden studio that has a sofa bed, a pull-out bed, or any fixed sleeping surface is NOT exempt — it contains sleeping accommodation
• •A garden studio with a futon or mattress occasionally placed in it MAY be treated as exempt if it is primarily used and designed as a studio — this is a grey area
• •Any outbuilding designed and marketed as an 'annex', 'garden bedroom', or 'garden guest suite' will be examined by Building Control as containing sleeping accommodation and will NOT be exempt from Building Regulations
• •The safest interpretation for compliance is: if the building is capable of being used for sleeping and is designed to be used by people who could reasonably sleep there, it is not exempt under Class 6

*Why sleeping accommodation matters for Building Regulations*: a building containing sleeping accommodation must comply with fire safety provisions (escape windows; smoke detection), structural requirements (adequate floor loading for bedroom furniture), and thermal and ventilation requirements. These provisions protect occupants who may be asleep when a fire occurs — the 10-minute escape time assumed for an awake occupant is not appropriate for a sleeping occupant.

**Important limitation: Schedule 2 exemptions apply to the building structure, not to services within it**:

One of the most common misconceptions about Building Regulations exemptions is that they exempt the entire project — including electrical work, drainage connections, and structural alterations. They do not. The Schedule 2 exemptions exempt the building structure from Building Regulations. Where electrical, drainage, plumbing, or other work is carried out in or in connection with the exempt building, those specific works may still be notifiable or may have their own compliance requirements.

**Electrical work in exempt buildings**:

Part P of the Building Regulations (Electrical Safety) applies to electrical work in and around dwellings — including work on outbuildings associated with the dwelling. The Part P provisions remain in force even where the outbuilding itself is exempt from Building Regulations under Schedule 2:

• •**Notifiable Part P work in an exempt outbuilding**: installing a new consumer unit; running a new circuit from the house to the outbuilding (the SWA armoured cable and the new circuit in the outbuilding); adding a new circuit in the outbuilding. All of this is notifiable to Building Control under Part P (either by a registered electrician self-certifying under a Part P competent persons scheme — NICEIC; Elecsa; NAPIT — or by the building owner notifying Building Control before works start)
• •**Non-notifiable Part P work in an exempt outbuilding**: adding a socket to an existing circuit; replacing an existing fitting like-for-like. Not notifiable

*In practice*: electrical work to connect an exempt garden room or outbuilding to the house supply is notifiable under Part P. Use a NICEIC-registered or NAPIT-registered electrician who self-certifies the work — this avoids the need for a formal Building Control inspection and provides an Electrical Installation Certificate (EIC), which is important for property sales.

**Drainage connections in exempt buildings**:

Connecting a WC, basin, or shower in an exempt garden room/outbuilding to the foul drainage system is not covered by the Schedule 2 exemption — it is notifiable under Part H of the Building Regulations (Drainage and Waste Disposal) if new drainage is being installed or extended.

*Exception*: where a garden room does not contain any WC, washbasin, or drainage connection, there is no drainage notification requirement. A dry studio or dry home office with no plumbing does not trigger Part H.

**Structural alterations to the dwelling to connect an exempt outbuilding**:

Where a wall or roof of the dwelling is altered to create a covered link or connection to an exempt outbuilding (e.g., an enclosed walkway from the house to the garden room), the structural alteration to the dwelling is NOT exempt — it requires Building Regulations approval regardless of the exempt status of the outbuilding itself.

**When to apply for Building Control approval rather than rely on an exemption — and why**:

*Reasons to apply for full Building Control approval even where a Schedule 2 exemption applies*:

1. **Property sales**: solicitors' enquiries (the TA6 Property Information Form) ask whether any building work has been carried out without Building Regulations approval and whether it was claimed to be exempt. An outbuilding claimed to be exempt under Schedule 6 without formal verification can attract questions from buyers' solicitors. A formal Application for Building Control Approval eliminates any ambiguity

2. **Insurance claims**: where an exempt outbuilding is damaged (fire; storm) and an insurance claim is made, the insurer may examine whether the building was constructed to a reasonable standard. An exempt building does not require compliance inspection, so the build quality may be unknown. A Building Control completion certificate provides evidence that the work was inspected and found satisfactory

3. **Class 6(a) boundary condition verification**: if the boundary distance or combustibility conditions for Class 6(a) are not clearly met (the building is close to the 1m boundary distance; the materials are borderline non-combustible), a formal check with Building Control before construction starts is sensible — confirming the exemption in writing before the building is constructed prevents disputes after completion

4. **Where the intended use may change**: a garden studio built as an exempt Class 6(b) structure might later be converted to sleeping accommodation — at which point it would require a retrospective Building Regulations inspection (which may result in remedial work requirements). If there is any intention to use the building for sleeping in future, build it to the Building Regulations standard from the start.

*How to formally confirm exemption*: contact the local authority Building Control (LABC) and ask for a written confirmation that the proposed building is exempt. This is not a formal application and typically carries no fee — it is simply a request for an informal opinion. Keep the written response for your records. Alternatively, apply for a formal 'regularisation' certificate after construction is complete, which provides a formal certificate of compliance (or exemption) for the building.