Glossary
The words you'll hear from designers, councils and builders, explained in a sentence or two.
- Article 2(3) land
- Protected land in England (conservation areas, National Landscapes, National Parks, World Heritage Sites, the Broads) where permitted development rights for extensions of more than one storey don't apply.
- Article 4 direction
- A council order that removes certain permitted development rights in an area, so a planning application is needed.
- Building control
- The service that checks building work meets the building regulations, run by councils or registered building control approvers.
- Building notice
- A quicker building regulations route with no plan approval in advance. Rarely suitable for two-storey work.
- Building warrant
- Scotland's approval to start building work, issued by the council's building standards service before work begins.
- Build-over agreement
- Permission from the water company to build over or near a public sewer.
- Cavity wall
- Two leaves of masonry with an insulated gap between them, the usual way new extension walls are built.
- Completion certificate
- The final sign-off confirming the work meets the building regulations or building standards.
- Curtilage
- The land within the boundary of a house, used to measure permitted development limits.
- Eaves
- The lower edge of a roof where it meets the wall. Permitted development limits eaves height.
- Escape window
- A first-floor window large and low enough to escape through in a fire: at least 0.33 m² clear opening, 450 mm wide and high, bottom no more than 1.1 m above the floor.
- Full plans application
- A building regulations application where drawings are checked and approved before work starts. Recommended for two-storey extensions.
- Hip and gable
- Roof shapes: a hip slopes on all sides, a gable has a vertical triangular end wall.
- Householder application
- The planning application used for extensions and alterations to a single house.
- Lawful development certificate
- A certificate confirming that work is lawful under permitted development. Scotland and Northern Ireland have an equivalent called a certificate of lawfulness of proposed use or development.
- Lintel
- A beam over a door or window opening that carries the wall above.
- Original house
- The house as first built, or as it stood on 1 July 1948 if older. Permitted development limits are measured from it.
- Padstone
- A concrete or engineering-brick block that spreads the load from a steel beam into a wall.
- Party wall
- A wall shared with a neighbour, or one on the boundary. Covered by the Party Wall etc. Act 1996 in England and Wales.
- Permitted development
- Building work that can be done without a planning application, within national limits and conditions.
- Principal elevation
- Usually the front of the house, facing the road. Nothing can go forward of it under permitted development.
- Principal designer / principal contractor
- Building Safety Act dutyholder roles in England when more than one contractor works on a project.
- RSJ / steel beam
- A rolled steel joist or universal beam that carries floors and walls over wide openings.
- Set-back and set-down
- Stepping a side extension back from the front wall and its ridge down from the main roof, so it reads as subordinate.
- Strip foundation
- A continuous trench of concrete under the walls, the most common foundation for extensions.
- Terracing effect
- When side extensions close the gaps between houses so a street looks like a terrace. Councils often resist it.
- Trial hole
- A small excavation to check the existing foundations and soil before the engineer finalises the design.
- U-value
- A measure of how much heat passes through a wall, roof, floor or window. Lower is better.
- 45-degree rule
- A guideline many councils use to judge loss of light to a neighbour's window. It varies by council.
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