Short answer: in England, most conservatories and porches don’t need a planning application, because they can be built under “permitted development” rights if they stay within set limits. For a conservatory, that broadly means a single-storey rear addition no deeper than 3 metres (4 metres on a detached house), no taller than 4 metres, and not forward of the front of the house. For a porch, the rule is a ground area of no more than 3 m², no higher than 3 metres, and at least 2 metres from any boundary with a road. Listed buildings, flats, some conservation areas and homes with an Article 4 Direction are the main exceptions. Both are usually exempt from Building Regulations too, with conditions.
This guide summarises the rules from the Planning Portal and the government’s permitted development technical guidance. It is general guidance for England, not legal advice. Always check with your council before you commit. For designs and options, see our conservatories and porches pages.
Conservatories: the permitted development limits
The Planning Portal says a conservatory “falls within the same set of planning rules as any other home extension” (Planning Portal). Those are the Class A rules in the General Permitted Development Order 2015, as amended. The main limits for a single-storey extension are:
- Land coverage: extensions and other buildings can cover no more than half the land around the “original house”. The government guidance says this 50% limit includes existing and proposed extensions, so an earlier extension or a large shed counts.
- Front and roadside: it cannot be built forward of the principal elevation, or forward of a side elevation that fronts a highway.
- Rear depth: no more than 3 metres beyond the rear wall of the original house, or 4 metres for a detached house.
- Height: no more than 4 metres for a single-storey rear extension, with eaves no higher than the existing eaves and no part higher than the existing roof.
- Near boundaries: within 2 metres of a boundary, the eaves height cannot exceed 3 metres.
- Side extensions: single storey only, no more than 4 metres high, and no wider than half the width of the original house.
One useful exception: the condition that materials must look similar to the existing house “does not apply to conservatories”, according to the government’s technical guidance. So a glazed conservatory on a brick house is acceptable under permitted development.
What “original house” means
The limits are measured from the house as it was first built, or as it stood on 1 July 1948 if it is older. If a previous owner added a rear extension, a new conservatory on the back of it may already exceed the depth limit. This is one of the most common reasons people find they need an application after all.
Bigger conservatories: prior approval for a larger home extension
You can go deeper than the standard limits, up to 6 metres for most houses or 8 metres for a detached house, using the prior approval process rather than full planning permission (Planning Portal). How it works:
- You apply to your council with a description and plans. The fee in England has been £249 from 1 April 2026 (North Yorkshire Council fee schedule).
- The council notifies adjoining neighbours, who can object.
- If anyone objects, the council judges the effect on neighbours’ amenity.
- You can’t start until the council confirms prior approval isn’t needed or is granted, or until 42 days have passed with no decision, according to the government’s technical guidance and Broxbourne Borough Council’s guidance note.
The larger home extension route is not available on Article 2(3) designated land, which includes conservation areas, National Landscapes and National Parks, or on Sites of Special Scientific Interest.
Porches: the 3 m² / 3 m / 2 m rule
Porches have their own, simpler rules under Class D. The Planning Portal says a porch is permitted development if:
- the ground floor area, measured externally, is no more than 3 square metres;
- no part is more than 3 metres above ground level; and
- no part is within 2 metres of any boundary that fronts a highway.
These rules apply to a porch outside any external door, not just the front door. In practice:
- Measuring externally matters. Wall or frame thickness counts towards the 3 m², so a porch that is roughly 1.5 × 2 metres on the outside is already at the limit.
- On a house with a short front garden, the 2 metre rule is usually the hardest to meet. Measure from the front boundary before you design anything.
- A pitched porch roof can reach 3 metres quickly on a two-storey house, so check the ridge height early.
If your porch idea is bigger than this, it isn’t ruled out. It simply needs a householder application, which costs £548 in England from April 2026.
Where permitted development rights don’t apply
- Flats and maisonettes do not have these householder permitted development rights, and nor do some houses created through change of use (Planning Portal).
- Article 4 Directions and planning conditions can remove permitted development rights. Historic England explains that councils use Article 4 Directions to protect particular local features and recommends asking your local planning authority whether one applies to your house (Historic England). Newer estates sometimes have conditions removing rights too, so check your planning history.
- Conservation areas and other Article 2(3) land: all side extensions need householder planning permission, exterior cladding isn’t permitted, and the larger home extension route isn’t available. A small rear conservatory may still be permitted development, if no Article 4 Direction applies.
- Listed buildings: Historic England says owners need Listed Building Consent “for most types of work” that affect the building’s special interest (Historic England). This applies even if planning permission is not required.
Many towns we cover, including Windsor and Eton, have extensive conservation areas, so this check is worth doing early. The same issues affect windows, and our planning permission for replacement windows guide covers them.
Building Regulations: usually exempt, with conditions
Conservatories
The Planning Portal says a conservatory is normally exempt when it is built at ground level and under 30 m², single storey, separated from the house by external-quality walls, doors or windows, has independent heating with its own controls, and its glazing and fixed electrics comply with the regulations. Two common traps:
- Knocking through. Any new structural opening between the house and the conservatory needs approval, even if the conservatory itself is exempt.
- Solid roofs. LABC guidance says that significantly reducing the glazing or translucence of the roof means the conservatory “can no longer be considered exempt” (LABC guide, via Test Valley Borough Council). See replacement conservatory roofs.
Porches
A porch is normally exempt if it is at ground level and under 30 m², its glazing and fixed electrics comply, the existing front door between the house and porch stays in place, and it doesn’t make level or ramped access worse for disabled people (Planning Portal). Removing that inner door turns the porch into part of the house, and approval is then needed.
Getting it in writing: Lawful Development Certificates
You don’t have to apply for anything if your project is permitted development. But a Lawful Development Certificate confirms it formally, and a buyer’s solicitor may ask for evidence when you sell. The fee is half the normal planning fee. If your plans are close to any of the limits, it’s worth getting one before work starts.
A simple checklist before you start
- Check whether your home is listed, in a conservation area, a National Landscape or National Park, or covered by an Article 4 Direction. Your council’s website usually has maps.
- Look up your planning history for previous extensions and conditions.
- Measure depth from the original rear wall, and distances to every boundary.
- Decide whether you want an inner door kept or removed, as this affects Building Regulations.
- Ask your council, or apply for a Lawful Development Certificate, if anything is borderline.
Talk to us about your conservatory or porch
When we survey, we’ll take the measurements that matter for planning and tell you where your design sits against the limits, so you can check with your council with the right information in hand. Call 01753 965 005 or request your free quote.
Frequently asked questions
Do I need planning permission for a conservatory?
Usually not, if it meets permitted development limits: single storey, no deeper than 3 metres from the original rear wall (4 metres for detached houses), no taller than 4 metres, not forward of the front of the house, and covering no more than half the land around the original house. Flats, listed buildings and Article 4 areas follow different rules.
How big can a porch be without planning permission?
In England a porch is permitted development if its ground floor area, measured externally, is no more than 3 square metres, no part is more than 3 metres high, and no part is within 2 metres of a boundary fronting a highway. This applies to a porch outside any external door. Anything larger needs a householder planning application.
Can I build a 6 metre conservatory without planning permission?
Possibly, through prior approval for a larger home extension, which allows single-storey rear extensions up to 6 metres, or 8 metres for detached houses. You apply to your council, the fee is £249 from April 2026, and neighbours are consulted. This route isn't available in conservation areas, National Landscapes, National Parks or Sites of Special Scientific Interest.
Does a conservatory need Building Regulations approval?
Normally not, if it is at ground level, under 30 square metres, single storey, separated from the house by external-quality walls, doors or windows, with independent heating controls and compliant glazing and electrics. Knocking through to the house, or replacing a glazed roof with a solid one, usually means Building Regulations approval is needed.
Can I build a porch or conservatory in a conservation area?
Often, but check first. In conservation areas side extensions need planning permission, cladding is restricted, and the larger home extension route isn't available. Many councils also use Article 4 Directions that remove further rights. If the house is listed, Listed Building Consent is likely to be needed. Your local planning authority can confirm what applies.