Renovation conversations are full of terms that get used casually by architects, builders, and contractors — and rarely explained to the people paying for the work. This glossary covers the terms that come up most often, in plain English, organised by the stage of a project where you’re most likely to hear them.

Planning and Permission Terms

Planning permission — Formal approval from the local council required for certain building works, particularly those affecting a property’s external appearance, footprint, or use. Not all work needs it; internal renovations generally don’t.

Permitted development rights — A set of rules allowing certain building works to proceed without a full planning application, provided they meet specific size, height, and location conditions. These rights can be restricted or removed entirely on some properties (see Article 4 direction, below).

Article 4 direction — A local council order removing some or all permitted development rights in a specific area, usually a conservation area, meaning work that would normally need no application must now go through full planning permission.

Conservation area — A designated area where a council has additional powers to control changes to buildings’ external appearance, in order to preserve the area’s character. Properties within one face tighter restrictions on things like windows, extensions, and materials.

Listed building — A property of special architectural or historic interest, protected by law. Any change affecting its character, inside or out, typically requires listed building consent, which is separate from and in addition to standard planning permission.

Pre-application advice — An informal (usually paid) consultation with a council’s planning department before submitting a full application, used to surface likely objections early while a design can still be adjusted cheaply.

Building regulations — A separate approval process from planning permission, concerned with whether construction is structurally safe and meets standards for fire safety, insulation, ventilation, and accessibility, regardless of whether planning permission was needed.

Party wall agreement — A formal agreement required under the Party Wall Act 1996 when building work affects a shared wall or boundary with a neighbouring property — common in London terraces and semi-detached houses. It protects both parties and is a separate legal process from planning permission.

Design and Technical Terms

Feasibility study — An early-stage assessment of whether a proposed project is actually achievable on a given site, covering planning context, structural constraints, and ground conditions, before design work begins in earnest.

Structural engineer — A specialist who calculates and certifies that structural changes (removing a wall, adding a steel beam, digging a basement) are safe and adequately supported, typically required for building regulations sign-off on any structural work.

Load-bearing wall — A wall that supports the structural weight of the building above it. Removing or altering one requires a structural engineer’s calculations and, usually, a steel beam or equivalent support to replace its function.

RSJ / steel beam — A steel beam (Rolled Steel Joist) installed to support a structure’s weight where a load-bearing wall has been removed, most commonly seen where a kitchen or living space has been opened up into a single room.

Building envelope — The physical barrier between a building’s interior and the outside world: roof, external walls, windows, and doors. Getting this “weathertight” is a key milestone in any structural project or new build.

Design and Technical Terms

Construction Stage Terms

First fix — The stage of construction where electrical wiring, plumbing pipework, and ventilation ducting are installed within a structure’s walls and floors, before they’re closed up with plasterboard or flooring. Mistakes at this stage are expensive to correct once walls are closed.

Second fix — The stage following first fix, where visible elements are installed: sockets, switches, light fittings, kitchen and bathroom fixtures, skirting, doors, and flooring. This is where a project starts to look finished.

Snagging / snagging list — A formal inspection, typically near project completion, identifying defects or unfinished details (a poorly fitted door, a paint touch-up needed, a fixture not working correctly) that must be resolved before final sign-off and payment.

Retention — A percentage of the total contract value withheld by the client until after snagging is complete and any defects resolved, used as an incentive for the contractor to properly finish and correct any issues.

Contingency — A budget reserve, typically 10-20% of total project cost, set aside for unexpected issues discovered during construction — particularly common and important in older properties.

Variation / variation order — A formal, priced change to the agreed scope of work, requested by either the client or contractor once a project is underway. A well-run project documents every variation in writing before proceeding, to avoid disputes over cost later.

Materials and Finishes Terms

Wet room — A fully waterproofed bathroom space with a level, curbless floor, allowing water to drain without a shower tray or step, requiring more careful waterproofing (tanking) than a standard shower.

Tanking — The waterproofing membrane or treatment applied to floors and walls in a wet room or bathroom before tiling, critical to preventing water damage to the structure beneath.

Fabric-first (retrofit) — An approach to improving a building’s energy efficiency that prioritises the building’s physical structure — insulation, glazing, airtightness — before or instead of relying solely on new heating technology.

U-value — A measure of how effectively a material (wall, window, roof) prevents heat loss; a lower U-value means better insulation performance, relevant when discussing window or insulation upgrades.

Project Management and Contract Terms

Design and build — A procurement approach where a single team is responsible for both designing a project and constructing it, as opposed to hiring a designer and a separate contractor independently.

Fixed price contract — A contract where the agreed price doesn’t change unless a formal variation is agreed in writing, offering more budget certainty than a contract priced on time and materials.

JCT contract — A standard form building contract (from the Joint Contracts Tribunal), commonly used in the UK for construction projects of meaningful scale, setting out each party’s obligations, payment terms, and how disputes are handled.

Practical completion — The point at which a project is considered essentially finished and usable, even if minor snagging items remain outstanding — often the trigger for final payment stages and warranty periods to begin.

NHBC warranty (or equivalent structural warranty) — A ten-year structural warranty commonly required for new build homes, covering major structural defects discovered after completion, often required by mortgage lenders.

Come across a term during your own renovation that isn’t listed here? At Alborz Groups, we’re happy to explain anything in plain English before you sign off on a quote or a contract you don’t fully understand. Get in touch for an initial consultation.

Renovation Terms Explained: A Plain-English Glossary