- Article 4 direction
- An order by a council withdrawing particular permitted development rights in a defined area. Liverpool City Council warns that works in conservation areas may be subject to one. Read more
- Class G
- The part of the national permitted development order covering air source heat pumps on houses and buildings of flats in England. Read more
- Conservation area
- An area of special architectural or historic interest designated by the council. Liverpool has 36. Read more
- Curtilage
- The land that goes with a building, such as its yard or garden. Class G rules about listed buildings extend to it. Read more
- Cylinder
- The insulated tank that stores hot water in most heat pump systems. Read more
- EPC
- Energy Performance Certificate, rating a home from A to G. The council's Warm Homes: Local Grant is for homes rated D to G. Read more
- Fronts a highway
- Faces onto a road or other highway. Class G treats road-facing walls and roofs more strictly, especially in conservation areas. Read more
- Heat network
- A shared heating system serving many homes from one plant room. Read more
- Lawful development certificate
- The council's formal confirmation that a proposal is lawful, for example because it meets Class G. Read more
- Listed building
- A building on the National Heritage List for England. The city has 1,569 listing records; Class G does not apply to them. Read more
- Listed building consent
- Separate consent for works that affect a listed building's special character, inside or out. Read more
- MCS 020 a)
- The MCS planning standard for air source heat pump sound, which a unit must meet to be permitted development. Read more
- Network operator
- The company that runs the local electricity network; in Liverpool, SP Energy Networks. Read more
- Permitted development
- Building work that has planning permission granted in advance by national order, provided it meets the conditions. Read more
- Pitched roof
- A sloping roof. Class G does not allow a heat pump on one. Read more
- Scheduled monument
- A nationally important archaeological site or monument. Class G does not apply on one. Read more
- Ward
- An electoral area of the city. Census results are published by ward. Read more
Terms the rules use differently
A few words mean something narrower in planning than in everyday speech. "Highway" is not only a main road: any public road, and public footpaths too, can be a highway, which is why a side wall on a corner can count as road-facing. "Curtilage" takes in a yard or garden as well as the building. Part 14 defines a "block of flats" as a building which consists wholly of flats, which is why a flat above a shop is a question for the council rather than a straightforward yes, and a "detached" house as one that shares no party wall with a neighbouring building, which is why a link-detached house may count as attached.