Can I build a conservatory?
Usually yes — a conservatory is treated as a rear or side extension under permitted development, and it's often exempt from Building Regulations too. For planning, it must stay within the same Class A limits as any extension: up to 3m deep (attached) or 4m (detached), max 4m high, not forward of the principal elevation, within the 50% garden rule, and in keeping; larger needs the 6m/8m prior-approval route. For Building Regulations, a conservatory is exempt only if it's at ground level, under 30m², single storey, and thermally separated from the house by external-quality walls, windows and doors, with its own independent heating controls. Safety glazing and Part P electrics still apply. If you remove the dividing doors, or it exceeds 30m², the exemption is lost. In short: usually yes, and often Building-Regs-exempt if kept separate.
📋 The rules
- Planning: same extension limits (3m/4m, 4m high, 50% rule)
- Larger (6m/8m) only via prior approval
- Building Regs exempt if under 30m², ground level, separated
- Needs independent heating controls, not on the house circuit
- Safety glazing and Part P electrics still apply
🔓 Exceptions
- Forming a structural opening into the house needs Building Regs
- Remove the dividing doors and the exemption is lost
- Listed buildings and designated land restrict it
⚠️ Penalties & fines
If a planning application is needed, the England householder fee is £548 and a Lawful Development Certificate about £274. The Building Regs exemption ceiling is 30m², at ground level only — go above either and full approval is needed. An unlawful build risks an enforcement notice (and even demolition) within the 10-year window, and missing approvals cause problems on resale. Beware a myth: "conservatories never need any permission or building control" is false — the exemption is conditional: exceed 30m², build above ground level, remove the thermal-separation doors, or sit on protected land, and approval is required. (Scotland uses an 8m² warrant-exemption figure, not 30m².) Before building: keep it under 30m² and thermally separated with closing doors and its own heating, and check the extension limits.
📎 Official sources
- Planning Portal — conservatories: building regulations →
- Planning Portal — conservatories: planning permission →
- GPDO 2015 →
❓ Frequently asked
Do I need planning permission for a conservatory?
Often not. A conservatory is treated as an extension under permitted development, so it usually doesn't need planning permission if it stays within the limits — generally up to 3 metres deep on an attached house or 4 on a detached one, no higher than 4 metres, not forward of the principal elevation, and within the 50% garden rule.
Is a conservatory exempt from Building Regulations?
It can be. A conservatory is exempt from Building Regulations only if it's at ground level, under 30 square metres in floor area, single storey, and thermally separated from the house by external-quality walls, windows and doors, with independent heating controls. If it doesn't meet all these, full Building Regulations approval is required.
What does 'thermally separated' mean?
It means the conservatory is divided from the rest of the house by walls, windows and external-quality doors of the same standard as the home's outside doors, and it has its own heating with separate controls, not connected to the main heating system. This separation is what allows the Building Regulations exemption to apply.
Can I knock through into my conservatory?
You can, but forming a structural opening by removing part of an external wall requires Building Regulations approval, even if the conservatory itself is exempt. And if you remove the separating doors so the conservatory becomes open-plan with the house, it's no longer thermally separated, so the exemption is lost and full approval is needed.
How big can my conservatory be?
For the Building Regulations exemption, it must be under 30 square metres of floor area and at ground level. For planning, it must stay within the extension size limits, typically up to 3 or 4 metres deep depending on the house, and within the 50% garden rule. Larger conservatories may need the prior-approval route or a full application.
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