Reference

Glossary

Plain-English definitions of the planning, building regulations and construction terms that come up during a home improvement project.

Planning

Article 4 Direction: A local order that removes some or all permitted development rights on specific streets, in specific conservation areas, or for specific property types — it applies locally, not nationally.
Certificate of Lawfulness: A formal document from the local planning authority confirming that a proposed or existing use or development is lawful, including under permitted development. Also called a Lawful Development Certificate.
Conservation Area: An area designated by the local authority for its special architectural or historic character, where planning controls are generally tighter and some permitted development rights are restricted.
Full Planning Permission: Permission granted for a specific, fully detailed proposal, as opposed to outline permission or a permitted development route.
Householder Planning Application: A planning application specifically for works to a single dwellinghouse (like an extension), rather than a full or outline application.
Larger Home Extension Scheme: A permitted development route allowing single-storey rear extensions beyond the standard depth limit, subject to a neighbour consultation and prior approval process rather than a full planning application.
Listed Building: A building of special architectural or historic interest, protected by law. Permitted development rights don't apply, and any alteration needs listed building consent as well as, where relevant, planning permission.
Listed Building Consent: Separate consent required, in addition to planning permission, for any work affecting the character of a listed building.
Local Planning Authority: The council department responsible for planning decisions in a given area — usually the district, borough or unitary authority.
Neighbour Consultation Scheme: The process behind the Larger Home Extension scheme, where the council notifies adjoining neighbours and considers their objections before confirming prior approval.
Outline Planning Permission: Permission that establishes whether a development is acceptable in principle, with detailed matters (design, access, etc.) approved separately afterwards.
Permitted Development: A national grant of planning permission allowing certain building works without a full planning application, subject to conditions and limits set out in the GPDO 2015.
Permitted Development Rights: The specific entitlements a property has under permitted development — these vary by property type and can be reduced or removed by an Article 4 direction, listing, or previous use of the allowance.
Planning Condition: A requirement attached to a grant of planning permission that must be satisfied, sometimes before work starts and sometimes before the building is occupied.
Planning Portal: The UK government's online service for planning applications and guidance, covering England and Wales.
Prior Approval: A check by the local planning authority on specific aspects of a permitted development proposal (like the Larger Home Extension scheme) before work can lawfully begin, distinct from a full planning application.
Retrospective Planning Permission: An application made for work that has already been carried out without the necessary permission. Not guaranteed to be granted, and can result in enforcement action if refused.
Site of Special Scientific Interest (SSSI): A land or water area protected for its wildlife, geology or habitat significance, where the Larger Home Extension permitted development route and some other rights don't apply.

Building Regulations

Approved Document: One of a series of official guidance documents (Part A structure, Part B fire safety, Part L conservation of fuel and power, and so on) explaining how to meet the Building Regulations in practice.
Building Control: The process of checking that building work complies with the Building Regulations, carried out either by the local authority or an approved private inspector.
Building Notice: A simpler Building Regulations submission for straightforward work, without detailed plans being checked in advance — inspections happen as the work progresses instead.
Building Regulations: The statutory minimum standards for the design and construction of buildings in England, covering structure, fire safety, insulation, ventilation, drainage and more — separate from planning permission.
Building Regulations Approval: Formal sign-off confirming that completed building work meets the Building Regulations, evidenced by a completion certificate.
Building Warranty: An insurance-backed guarantee (such as an NHBC or similar warranty) covering structural defects for a set period, common on new builds and sometimes obtained for major extensions.
Completion Certificate: The document confirming Building Regulations approval has been granted for finished work — worth keeping for any future sale of the property.
Full Plans Application: A Building Regulations submission with detailed drawings and specifications, checked before work starts, as opposed to a Building Notice.
Structural Calculations: The engineering calculations, produced by a structural engineer, showing that a proposed structural element (like a steel beam over a knocked-through wall) is adequate — usually required for Building Regulations approval.
Structural Engineer: A qualified professional who designs and calculates structural elements — beams, foundations, load paths — to ensure a building or alteration is safe and compliant.
U-value: A measure of how much heat passes through a building element (wall, roof, window). Lower U-values mean better insulation, and the Building Regulations set minimum standards for new and altered elements.

Construction

Cavity Wall: External wall construction with two masonry layers separated by a gap (cavity), often filled or fitted with insulation — standard in most UK homes built after the 1920s-30s.
Dormer Window: A structure projecting vertically from a sloped roof, creating extra headroom and floor space inside — the basis of a dormer loft conversion.
Eaves: The lower edge of a roof, overhanging the wall — the point permitted development height limits near a boundary are measured to.
Foundations: The structural base of a building, transferring its load safely into the ground. Type and depth depend on ground conditions and the load being carried.
Gable: The triangular section of wall at the end of a pitched roof, between the two roof slopes.
Hip Roof: A roof with sloped sides on all four sides, meeting at a ridge — as opposed to a gable roof, which has vertical wall sections at each end.
Lintel: A horizontal structural support placed above a door or window opening to carry the load of the wall above.
Load-Bearing Wall: A wall that carries structural weight from above, as opposed to a stud partition wall that doesn't. Removing one always needs a structural engineer and, typically, a steel beam.
Mansard Roof: A roof with a steep lower slope and a shallower upper slope, often created by significantly rebuilding the rear roof of a terrace to maximise loft space.
Purlin: A horizontal structural roof timber supporting the rafters, often needing to be strengthened or repositioned during a loft conversion.
Render: An external wall finish, typically cement- or lime-based, applied over masonry or blockwork for weatherproofing and appearance.
Ridge: The horizontal line at the top of a pitched roof, where two roof slopes meet.
Rooflight: A window fitted flush with the plane of the roof (a common brand name is Velux), used in the simplest, lowest-impact type of loft conversion.
Screed: A layer of material (often sand and cement, or a flowing self-levelling compound) laid over a floor structure to create a smooth, level surface for the final floor finish, and sometimes to contain underfloor heating pipework.
Steel Beam (RSJ): A steel joist used to support a structural opening, most commonly where a wall is removed to create an open-plan space. Sized by a structural engineer's calculations.
Trench Fill Foundation: A common foundation type for extensions, where a trench is dug and filled with concrete close to ground level, rather than built up in courses of brick or block.
Underpinning: Strengthening or extending existing foundations, usually to correct subsidence or to support a new structural load such as a basement or additional storey.

Party Wall

Adjoining Owner: The owner of a property next to the one where work covered by the Party Wall etc. Act 1996 is being carried out — the person a notice must be served on.
Party Wall: A wall (or, in some cases, a garden boundary wall or excavation near a boundary) shared between two properties, or standing on the boundary line between them, covered by the Party Wall etc. Act 1996.
Party Wall Award: The legal document produced by a party wall surveyor (or surveyors) setting out how the work will be carried out and protecting both parties' interests, once a notice has been served and not simply agreed without one.
Party Wall Notice: A formal written notice served on an adjoining owner before starting work covered by the Party Wall etc. Act 1996, giving them the required notice period to respond.
Party Wall Surveyor: A surveyor appointed under the Party Wall etc. Act 1996 to produce a party wall award — either a single 'agreed surveyor' for both parties, or one appointed by each side.
Schedule of Condition: A record (often photographic) of the condition of a neighbouring property before work starts, used to establish whether any damage occurred as a result of the works.

Process

First Fix: The stage of construction covering structural work, and the initial installation of electrical cabling, plumbing pipework and stud walls, before plastering.
Groundworks: Excavation, foundations, drainage and other below-ground work carried out at the start of a build, before the structure above ground begins.
Practical Completion: The point at which the works are complete enough for the client to take possession and use the space, even if minor snagging items remain outstanding.
Prime Cost Sum (PC Sum): An allowance in a quote for a specific item (like sanitaryware or kitchen units) where the exact product hasn't been chosen yet — the final cost is adjusted once it is.
Provisional Sum: An estimated allowance included in a quote for work that can't be priced precisely until more information is known (for example, the condition of something only visible once other work has started).
Retention: A percentage of the contract sum withheld until after practical completion (and sometimes until after a defects period), as a safeguard to ensure snagging and any defects are addressed.
Second Fix: The stage after plastering, covering the final installation of sockets, switches, taps, doors, skirting and other finishing items.
Snagging: The process of identifying and listing minor defects or unfinished details at the end of a project, for the contractor to put right before final completion.
Variation: A change to the agreed scope of work after a contract has started, whether requested by the client or required because of something discovered on site — normally priced and agreed before proceeding.