Sophie Bennett
Start with the rules, not the drawings
It is tempting to sketch a rear extension and assume the paperwork will follow. In the UK, the application you need depends on the work, the property and the local area. A full planning application is the detailed route for development not covered by permitted development rights or a householder application. If you are extending a house within permitted limits, you may only need a certificate of lawfulness. If you are changing a building's use, altering a listed structure or creating flats, you usually need full planning permission. Check local policies and confirm the application type before you commission drawings.
Extensions and permitted development
Permitted development (PD) rights allow certain extensions and alterations without a planning application. For a single house, typical limits include a single-storey rear extension of up to 3 metres for attached properties and 4 metres for detached ones. Two-storey rear extensions can project 3 metres, with a maximum height of 7 metres and eaves at 3 metres. Side extensions, dormers and outbuildings each have their own rules.
Flats and maisonettes have no PD rights for extensions. Article 4 directions remove rights in many streets and conservation areas. If your scheme exceeds a threshold or sits in a sensitive location, you need a formal application – usually a householder application for a house, or a full planning application for anything else.
Projects that almost always need permission include two-storey side extensions, wraparound extensions, balconies, raised terraces, basements, front extensions and annexes that could become a separate dwelling. Any extension to a listed building also needs listed building consent. Even if within PD, building regulations may still apply.
Changes of use: the class system explained
Use classes group buildings by what they are used for. In England, Class C3 covers dwellinghouses, Class C4 covers small houses in multiple occupation, and Class E covers shops, offices and restaurants. Some changes of use are permitted development, often subject to prior approval. For example, Class E to C3 residential conversion has a prior approval route. But many changes need full planning permission, including converting a house into flats, changing a dwellinghouse into an HMO where an Article 4 direction removes the C3 to C4 right, and changing a shop or office into a hot food takeaway, betting shop or pub. Mixed-use schemes and changes that conflict with local plan policies also need full permission. Always check the current use class and any local restrictions.
Listed buildings and conservation areas
Listed buildings need listed building consent for works that affect their character as buildings of special architectural or historic interest. That can include internal alterations, replacing windows, inserting a staircase or removing historic fabric. You may also need full planning permission for external alterations, extensions or a change of use. In conservation areas, planning permission is required for certain demolition, cladding and extensions that would be permitted development elsewhere. Article 4 directions can remove PD rights for small works such as painting or window replacement. Trees in conservation areas need six weeks' notice before works. Involve the conservation officer early. A heritage statement is usually required, explaining how your proposals preserve or enhance the special interest of the building or area.
Check local policy before you design
Local planning authorities decide applications against their local plan, neighbourhood plan and design guides. These policies can require a certain roof pitch, brick colour or parking provision, and may protect views, trees or wildlife corridors. Before you finalise drawings, read the relevant policies and check for Article 4 directions. Pre-application advice is worth the fee. It gives you a written steer from a planning officer and can highlight flood risk, highways access or heritage impact. It is not binding, but it often saves months of redesign.
Validation is another hurdle. Most councils publish a checklist. Typical requirements include a site location plan, existing and proposed plans and elevations, a design and access statement, a heritage statement, a flood risk assessment and a tree survey. You must also complete an ownership certificate and notify other owners. Missing documents can delay your application by weeks.
A strong application is clear, consistent and policy-aware. Use accurate drawings and a covering letter that addresses local plan policies head-on. Show how your scheme respects neighbours' amenity, light and privacy. Householder applications are usually decided within 8 weeks, and full applications within 13 weeks. If refused, you can usually appeal within six months. Never start work before permission, especially for listed building consent. A little homework at the start pays back in smoother approvals.
