Home Renovation Glossary 

Think a hip is just at the top of your leg, or a gypsum lives in your garden? You’re not alone. The moment a renovation starts, you’re suddenly expected to know your joists from your jambs, your lintels from your listed building consent, and it can leave even the most organised homeowner feeling out of their depth.

This A to Z glossary breaks down the construction terms, building regulation language and architectural jargon we use every day, whether you’re planning an extension, reading through a survey report, or just trying to understand what your builder meant by “making good.” No jargon, no waffle, just plain explanations so you can follow the conversation confidently from day one.

A

Abutment: An intersection point where one building element meets another, typically where a roof joins a wall. This connection is crucial for understanding structural integrity and identifying potential areas susceptible to water ingress.

Access Rights: Legal entitlements that permit an individual to enter or pass over another’s land for a specific, defined purpose. These rights are fundamental in property law, particularly concerning shared access, utility easements, or boundary considerations within residential developments.

Airbrick: A perforated brick, terracotta, or plastic vent integrated into a wall to facilitate ventilation. These are commonly used to ventilate the void beneath timber ground floors, within fireplaces, or in roof spaces. Proper air circulation is vital for preventing damp, mould, and ensuring adequate airflow in both older and new residential properties.

Architrave: A moulded surround, typically decorative, applied to a door or window opening. Its primary function is to conceal the joint between the frame and the wall finish, hiding any shrinkage gaps. This is a common architectural detail that influences the aesthetic and finish of internal spaces.

Asbestos: A hazardous material once commonly used in building construction and insulation. Its presence in a residential property requires specific surveying and management, often needing specialist advice if suspected or found.

B

Balustrade: A collective term referring to a railing system composed of upright supports (balusters) that form a protective barrier. Commonly found along staircases, balconies, or parapets in multi-level residential properties, serving as a key safety feature and design element.

Batten: Thin strips of timber primarily used to support roof tiles or slates, or for fixing drylining to internal walls. Battens are a fundamental component in roof construction and internal wall finishes, affecting both structural integrity and insulation performance.

Building Control: The regulatory process that ensures building work complies with minimum standards for health, safety, fuel conservation, and accessibility, enforced by local authorities or approved inspectors. It’s a mandatory part of any new build, extension, or significant alteration in the UK, and operates distinctly from planning permission.

Building Regulations: Statutory requirements in the UK that establish minimum standards for the design and construction of most new buildings and many alterations to existing ones, focused on health, safety, and energy efficiency. These regulations form the overarching legal framework guiding construction practice, with detailed guidance provided in Approved Documents.

Buttress: A mass of masonry built against or projecting from a wall, used to stabilise the wall, often to resist the lateral thrust of an arch, roof, or vault, or to allow the wall to be thinner.

C

Casement Window: A window type where one or more sashes are hinged, typically at the side, to open outwards like a door. This is one of the oldest and most common window styles in the UK, adaptable to various property types and materials.

Cavity Wall: A prevalent external wall construction method consisting of two separate “leaves” (typically an outer brick skin and an inner block skin) with a continuous gap between them. In modern buildings, this cavity is often filled with insulation, making it central to understanding thermal and damp issues.

Cesspool (Cesspit): A sealed underground tank that collects sewage and wastewater without draining, requiring regular emptying by a waste carrier. During a building survey, surveyors assess a cesspit’s condition, leakage, and maintenance accessibility, since it’s a significant consideration when purchasing a property.

Cladding: A non-load-bearing external skin applied to a wall or roof, primarily for weather protection and aesthetic enhancement, used in various modern and traditional residential buildings.

Condensation: Water droplets forming on a surface when warm, moist air cools upon contact with a colder surface, often leading to dampness and mould growth. This is a common issue in properties with inadequate ventilation or insulation, directly affecting indoor air quality and the building fabric.

D

Damp-Proof Course (DPC): An impermeable layer of material, such as bitumen felt, PVC, or slate, installed in walls around 150mm above ground level, to prevent rising dampness from penetrating the building structure. This is a fundamental Building Regulations requirement for preventing moisture ingress.

Damp-Proof Membrane (DPM): A thin, impervious sheet, usually polythene or bitumen, laid horizontally beneath a floor slab or finish to prevent rising dampness from the ground affecting the floor structure. It’s essential for solid ground floors to ensure a dry and healthy internal environment.

Demolition: The partial or complete dismantling or removal of a structure, which typically requires prior notification to the local council and may need specific planning permission.

Dormer (Window): A vertical window structure that projects from a sloping roof, often with its own roof, designed to provide natural light and increase head height within loft spaces. A common feature in loft conversions, subject to specific planning and building control rules.

Dry Rot: A highly destructive form of timber decay caused by the fungus Serpula lacrymans, which thrives in damp, unventilated conditions and can spread rapidly through masonry. It’s a serious structural defect requiring specialist treatment, often identified during the kind of drone and thermal imaging surveys we use to check a property before design work starts.

E

Eaves: The lower edge of a roof that typically overhangs the walls of a building, protecting the walls from rainwater and providing the location for gutters and fascia boards.

Energy Performance Certificate (EPC): A document providing information on a property’s energy efficiency and carbon emissions, mandatory when properties are constructed, sold, or let in the UK.

Engineering Brick: A particularly strong and dense type of brick, used in applications requiring high compressive strength or superior resistance to water, such as damp-proof courses in older buildings or retaining walls.

External Wall Insulation (EWI): A system of insulation fitted to the outside of a house, typically finished with a new render or cladding system, and a significant retrofit measure for improving energy efficiency in solid wall properties.

F

Fascia Board: A vertical board fixed along the roof eaves, to which rainwater gutters are often attached, contributing to both weather protection and the overall aesthetic finish of a building.

Fibreboard: A soft, porous building board used for insulation and lining. Modern versions offer improved fire safety compared with some older types.

Flashing: A strip of impervious material, such as lead or zinc, used to seal the junction between a roof and a wall, chimney, or other projection, critical for keeping a building weather-tight.

Fixed Window: A window that cannot be opened, used primarily for admitting light and for aesthetic purposes, often in areas where ventilation isn’t required or is provided by other means.

Spotlight: what is a “fabric-first” approach?

A “fabric first” approach to building design and renovation prioritises optimising the energy performance of a building’s physical components, its envelope, including walls, roof, floor, windows, and doors, before integrating mechanical or electrical systems like heating or ventilation. It uses high-performance materials with a strong focus on reducing thermal bridging, increasing airtightness, and achieving low U-values, and is a foundational strategy for sustainable construction.

This approach can significantly cut the energy needed for heating or cooling a space, leading to lower running costs, reduced maintenance, and a more comfortable home. It applies equally to new builds, where it can support standards like Passivhaus, and to existing renovations, where it’s usually the sensible first step in a wider retrofit. Improving the insulation of walls, lofts, and floors is the most common starting point.

By improving a building’s inherent thermal performance first, a fabric-first approach reduces reliance on active heating and cooling systems, making a home more resilient to future energy price changes and the shift from gas boilers to heat pumps. A well-insulated, airtight shell performs well whatever the heat source, which is why it’s worth getting right before investing in renewable technology.

G

Gable: The triangular upper part of an end wall, formed by the slopes of a pitched roof, a defining architectural feature that significantly influences roof design and external appearance.

Ground Heave: The upward movement of ground, typically clay soil, caused by expansion and swelling when it absorbs moisture. This can cause significant damage to building foundations and often requires careful foundation design or remedial action.

Gully: An opening at ground level into which rainwater and waste water are collected before entering the main underground drainage system, preventing surface water building up around a property.

Gutter: A channel along the eaves of a roof, designed to collect and convey rainwater away from the building, protecting the facade and foundations from moisture damage.

Gypsum: A common mineral widely used as a modern plaster material, notably in plasterboard and plaster skim finishes, extensively used in modern internal construction for walls and ceilings.

H

Hardcore: Broken bricks, stone, or other inert materials, consolidated to form a stable base under floors, patios, or foundations.

Heave: (See Ground Heave) The upward movement of foundations or floors, primarily due to the expansion of clay sub-soil when it absorbs moisture, distinct from settlement, which involves downward movement.

Hip: The sloping angle or external line formed at the junction of two roof planes that meet to form a ridge, typically occurring at the end of a roof that doesn’t terminate with a gable.

I

In Situ: A term describing construction work or materials cast, formed, or assembled directly in their final position on site, rather than being prefabricated elsewhere.

Infill: Material, often hardcore, laid beneath a solid floor or within a cavity to provide support or insulation, essential for a stable and insulated base.

Inspection Chamber: Commonly known as a “manhole,” this is an access point to an underground drain or sewer, allowing for inspection, maintenance, and clearing of blockages.

Internal Wall Insulation (IWI): Insulation fitted to the inside of external walls, typically behind drylining or plasterboard, used to improve thermal performance where external insulation isn’t feasible.

J

Jamb: The vertical side face of a doorway or window opening, forming the structural and aesthetic framing for openings in walls.

Japanese Knotweed: An invasive plant species (Fallopia japonica) that can cause significant damage to building foundations and structures. Its presence can severely impact property value and mortgageability, often requiring specialist eradication.

Joist: A horizontal timber or steel beam that directly supports a floor, ceiling, or flat roof, forming part of a building’s internal framework, and crucial for load distribution and stability.

Joist Hanger: A steel shoe or bracket designed to support the end of a joist, typically where joists connect to a beam or wall.

K

Kerb: A profile, often of shaped timber, fixed to a flat roof deck abutting an adjacent wall but not fixed to it, typically used for drainage or edge retention.

Key: The roughness or texture of a surface that provides a mechanical bond or grip for subsequent applications, essential for the adhesion and durability of paint, plaster, render, or tiles.

Kitchen Extract: A ventilation system, typically a fan or extractor hood, designed to remove odours, steam, and pollutants from a kitchen, often ducted to the outside and important for compliance with Building Regulations Part F.

L

Lath and Plaster: A traditional method of constructing internal walls and ceilings using thin timber strips fixed to a frame, over which wet plaster is applied. Common in older properties, known for breathable qualities but susceptible to cracking over time.

Lintel: A horizontal beam, often timber, concrete, or steel, positioned over a door or window opening to support the load of the wall above it, a critical structural element for the stability of openings in load-bearing walls.

Load-Bearing Wall: An active structural component of a building that supports the weight of elements above it, such as floors, roofs, or other walls. Their removal or alteration requires professional assessment and adequate structural support.

Loft Conversion: The process of transforming an unused attic or loft space into habitable living accommodation. This can often be undertaken under permitted development rights, though some projects need full planning permission, subject to specific height, volume, and window restrictions.

M

Macerator: An electrical device connected to a WC that grinds and pumps waste through small-diameter pipes, allowing WCs to be installed away from main soil pipes or in basements where gravity drainage isn’t feasible.

Mansard Roof: A pitched roof design with a shallower upper slope and a steeper lower slope on each side, often incorporating dormer windows to create usable attic space, popular in urban residential properties.

Mastic: A generic term for any permanently plastic, sticky, and waterproof material used for sealing exterior joints, such as around windows or in roofing applications.

Mechanical Extract Ventilation (MEV): A continuous ventilation system that uses a centrally located mechanical fan and ductwork to extract air from “wet rooms,” often combined with trickle vents for background ventilation, designed to maintain indoor air quality and control humidity.

Mortar: A mixture of sand, cement, water, and sometimes lime, used to bind bricks, blocks, or stones together in masonry construction, and also used for pointing joints.

N

Newel Post: A stout vertical post that supports a staircase handrail at the top, bottom, or a landing, a key structural and aesthetic component of staircases.

Noggins: Short horizontal timbers inserted between vertical studs in a framed partition wall, providing stiffness and secure fixing points for plasterboard or other finishes.

Nosing: The overhanging edge of a stair tread, which typically projects beyond the riser below it, a design and safety feature often incorporating anti-slip elements.

O

Ogee: An architectural moulding profile characterised by a double curve, where a concave arc flows into a convex arc, often seen in gutters or cornices and particularly common in Victorian architecture.

Oriel (Window): A projecting window bay, often supported by corbels or brackets, that doesn’t extend to the ground level, adding architectural interest and increasing internal light and space.

Oversite Concrete: A concrete slab laid over the earth beneath the ground floor of a house, forming a stable, often damp-proof base for solid ground floors.

Oversailing: A projecting course of brickwork or masonry that extends beyond the face of the wall below, either an intentional decorative feature or, if unintended, an indication of structural movement.

P

Panelled Door: A door constructed with a framed surround, where the spaces within the frame are filled with thinner panels, typically timber. A traditional door style, common in period residential properties.

Parapet: A low wall built along the edge of a roof, balcony, or terrace, often extending above the roofline, providing a safety barrier and influencing a building’s silhouette.

Party Wall: A wall that stands on the boundary of land belonging to two or more different owners, or that separates buildings belonging to different owners. Party walls are subject to the Party Wall etc. Act 1996, which governs alterations and works affecting them; if you’re planning works that affect a shared wall, you’ll usually need a party wall agreement, something we’ve written about in more detail in our guide to telling neighbours about building work. For the full legal detail, the Party Wall Act guidance on gov.uk sets out exactly what’s required.

Permitted Development: A nationwide planning permission granted by the UK Government (via the Town and Country Planning (General Permitted Development) (England) Order 2015), allowing certain limited forms of development, such as extensions or outbuildings, without a specific planning application. It offers homeowners flexibility for minor works but is subject to strict conditions, limitations, and potential Article 4 Directions. For the full legal detail, the Planning Portal is the clearest official source.

Purlin: A horizontal beam within a roof structure that provides intermediate support to the rafters, typically spanning between gables or main trusses.

Q

Quantity Surveying: A professional service within the construction industry focused on managing construction costs, from initial feasibility studies to final accounts, essential for budget control in residential development and renovation.

Quoin: The external corner of a wall, often emphasised by distinctively cut or contrasting bricks or stone blocks, serving both decorative and structural purposes.

R

Rafter: A sloping timber or steel beam that forms part of the internal framework of a pitched roof, extending from the ridge to the eaves, and the primary structural element supporting the roof covering.

Radon Gas: A naturally occurring, colourless, odourless radioactive gas found in some geological areas of the UK, which can accumulate in buildings. Specific mitigation measures are required in affected areas to comply with Building Regulations Part C.

Render: A coat of mortar (cement or lime-based) applied to the external or internal face of a wall for a smooth, textured, or weather-resistant finish, affecting aesthetics, weather protection, and thermal performance.

Retrofit: The process of adding new or upgraded features and technologies to an existing home to improve its energy efficiency and overall performance, a critical strategy for decarbonising the existing UK housing stock.

Rising Damp: Moisture that soaks up a wall from the ground by capillary action, often causing timber rot, plaster decay, and damage to decorations, requiring an effective damp-proof course for mitigation.

S

SAP Calculation (Standard Assessment Procedure): The UK Government’s mandatory methodology for calculating and assessing the energy performance of new and existing residential dwellings, forming the basis for regulatory compliance and Energy Performance Certificates.

Sash Window: A window type typically featuring two framed panels that slide vertically past each other within a cased frame, often counterbalanced by weights. A classic style particularly prevalent in Georgian, Victorian, and Edwardian properties.

Screed: A layer of mortar, typically 50 to 75mm thick, laid over a concrete floor to provide a smooth, level finish for subsequent floor coverings.

Septic Tank: A private drainage installation where sewage decomposes through bacterial action, with treated liquids dispersing into the ground or a soakaway, an alternative to mains drainage requiring regular maintenance.

Subsidence: The downward movement of a building’s foundations due to shrinkage or failure of the underlying ground, often caused by clay shrinkage from trees or leaking drains. A serious structural defect requiring expert investigation and often costly remedial works like underpinning.

T

Tanking: The application of a waterproof membrane to the internal surfaces of a basement or cellar to prevent water penetration, essential for converting basements into habitable spaces.

Tell-tale: A small gauge or strip fixed across a crack in a wall to monitor and measure any subsequent movement, a simple but effective tool used by surveyors to assess structural cracking.

Tie Bar: A metal bar passing through a wall or walls, often with external plates, used to brace and restrain a structure suffering from lateral movement or bulging.

Trickle Vent: A small, controllable opening, typically integrated into a window frame, that allows continuous background ventilation, helping maintain air quality and prevent condensation.

Truss: A prefabricated triangular framework of timbers or steel, commonly used in modern roof construction to replace traditional rafter and purlin systems.

U

Underpinning: The process of strengthening or extending existing foundations by excavating beneath them and inserting new, stronger foundations, a common remedial measure for properties affected by subsidence.

uPVC (Unplasticised Polyvinyl Chloride): A rigid plastic material widely used in the UK for window frames, doors, rainwater gutters, and other building components, popular for its durability and low maintenance.

Spotlight: U-values

A U-value, also called a heat transfer coefficient or thermal transmittance, measures how effective a building element, such as a wall, roof, floor, or window, is as an insulator, and how quickly heat passes through it from inside to outside. A lower U-value means better insulation, so less energy is needed to keep a home comfortable. This is fundamental to assessing and improving the energy efficiency of a property, and directly affects heating costs and carbon emissions.

U-values were first written into UK legislation in 1965, with requirements becoming steadily more stringent in 2002 and again in 2013. The Future Homes Standard, due in 2025, aims to cut carbon emissions and energy loss from new homes by 75 to 80% compared with current standards, part of a clear direction of travel towards highly energy-efficient, low-carbon homes.

Even with rigorous calculations and strict targets, there’s often a gap between the U-value predicted on paper and the thermal performance a building actually achieves. This “performance gap” tends to come down to workmanship, poor detailing, or moisture trapped in insulation materials, which is why good on-site quality control matters just as much as good design.

V

Valley: The internal intersection or channel formed where two sloping roof surfaces meet, designed to collect and drain rainwater. A vulnerable point in roof design requiring careful detailing and flashing to prevent leaks.

Vapour Barrier (Vapour Control Layer): An airtight membrane used within a building’s construction to prevent moisture vapour passing from the warm side to the cold side of insulation, where it could condense, protecting insulation and structural timbers.

Ventilation: The process of supplying and removing air from indoor spaces to maintain air quality, control temperature, and manage humidity and condensation, essential for healthy living environments and compliance with Building Regulations Part F.

Verge: The edge of a sloping roof that overhangs a gable wall, often protected by an undercloak and verge tiles, a key detail in protecting the gable end from weather.

W

Wall Plate: A horizontal timber beam laid along the top of a wall, distributing the load from and providing a secure fixing point for roof rafters or floor joists.

Wall Tie: Metal fixings embedded into the inner and outer leaves of a cavity wall to connect and strengthen the two skins, preventing them from bowing or collapsing.

Weatherboard: Overlapping timber or uPVC boarding used as external wall cladding, providing weather protection and a distinctive aesthetic.

Weep Holes: Small drainage holes or gaps intentionally left in brickwork, particularly at the base of cavity walls or behind retaining walls, allowing trapped water to escape.

Wet Rot: A form of timber decay caused by various fungi thriving in consistently damp conditions, generally less difficult to eradicate than dry rot, but still requiring identification and rectification of the moisture source.

Z

Zero Carbon Home: A dwelling designed and constructed to achieve net-zero carbon emissions over its lifecycle, typically through a combination of high energy efficiency and on-site renewable energy generation.

Zone (Conservation Area): A designated area recognised for its special architectural or historic interest, where stricter planning controls apply to preserve its character. This often restricts permitted development rights, and comes up frequently in the Victorian renovations we work on across London. For guidance on what applies to a listed building or a property within a conservation area, Historic England is the best place to check.

Still not sure what applies to your project? Our what we do page explains the different ways we can get involved, from architectural design through to full design and build, and our process page walks through how a project actually unfolds once you’ve decided to go ahead.

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