Home Improvement Glossary

Article 4 direction: An Article 4 direction is an order made by a council in England or Wales that removes specific permitted development rights in a defined area, so that work such as replacing windows, altering front walls or painting brickwork needs planning permission. Scotland and Northern Ireland have similar powers to restrict permitted development.
Building control: Building control is the service that checks building work complies with Building Regulations, through plan checks and site inspections. In England and Wales it can be the council or a registered private body; in Northern Ireland it is the council. In Scotland, the equivalent council service is called building standards.
Building Regulations: Building Regulations are legal minimum standards for how building work is designed and built, covering structure, fire safety, insulation, ventilation, drainage and more. They apply separately from planning permission. England, Wales and Northern Ireland each have their own Building Regulations, while Scotland has building standards enforced through building warrants.
Building warrant: A building warrant is the approval needed in Scotland before starting most building work, including extensions, loft conversions and structural alterations. It is granted by the council's building standards service after checking drawings against the Scottish building standards. Starting work that needs a warrant without one is an offence.
Competent person scheme: A competent person scheme is a government-authorised scheme in England and Wales that lets registered installers self-certify certain work, such as replacement windows, boilers and electrical work, as meeting Building Regulations without a separate building control application. The installer notifies the council, and you receive a certificate.
Completion certificate: A completion certificate is the document confirming that building work has been inspected and meets the Building Regulations. In England, Wales and Northern Ireland it is issued by building control when the work is finished. In Scotland, a completion certificate is submitted to the council, which accepts it once satisfied. Keep it for when you sell.
Conservation area: A conservation area is an area of special architectural or historic interest designated by the council to protect its character. Permitted development rights are reduced there, so work such as side extensions, cladding, roof changes and some demolition can need planning permission. Work to trees usually needs advance notice to the council.
Damp-proof course (DPC): A damp-proof course is a waterproof layer built into a wall, usually at least 150 mm above outside ground level, to stop moisture rising from the ground into the wall above. Modern damp-proof courses are plastic sheet; older houses may have slate, bitumen felt or none at all.
Damp-proof membrane (DPM): A damp-proof membrane is a sheet of heavy-duty polythene or a liquid coating laid under or within a ground floor to stop moisture rising from the ground. It should link with the damp-proof course in the walls to form a continuous barrier, and is needed in extensions and garage conversions.
Dormer: A dormer is a structure that projects from a sloping roof, with its own window, walls and roof, to create extra head height and floor space inside. Rear dormers are the most common type of loft conversion on terraced and semi-detached houses, and some fall within permitted development, depending on the nation and the property.
Dropped kerb: A dropped kerb, or vehicle crossover, is a lowered section of kerb and strengthened pavement that lets vehicles cross from the road to a driveway. It must be approved by the highway authority, usually the council, or the Department for Infrastructure in Northern Ireland, and is often built by the authority or its approved contractor.
EPDM: EPDM is a synthetic rubber membrane used to cover flat roofs. It is usually laid as a single large sheet with few joints, bonded to the roof deck, and stays flexible in hot and cold weather. EPDM suits simple roof shapes such as extensions, garages and dormers.
Fascia: A fascia is the long, straight board fixed along the lower edge of a roof, across the ends of the rafters. It supports the gutters and the bottom row of tiles. Fascias are usually uPVC or painted timber and are often replaced together with soffits and guttering.
First fix: First fix is the stage of a building job when hidden services and structure go in before walls and ceilings are plastered, including electrical cables, back boxes, water and waste pipes, heating pipes, ductwork and door linings. Changes cost least at this stage, before everything is covered up.
Flashing: Flashing is a strip of weatherproof material, traditionally lead, that seals the joint where a roof meets a wall, chimney, roof window or another roof. Lead flashing is tucked into a mortar joint and dressed over the roof covering. Failed or lifted flashing is a common cause of roof leaks.
GRP: GRP, or glass-reinforced plastic, is a flat roofing system often called fibreglass. Resin and glass-fibre matting are laid over a timber deck to form a seamless, hard-wearing surface, then finished with a coloured topcoat. It is often used on flat roofs over extensions, dormers and garages.
Hip-to-gable: A hip-to-gable loft conversion replaces the sloping hipped roof at the side of a house with a vertical gable wall, extending the ridge to create more usable loft space. It is common on semi-detached and detached houses with hipped roofs, and is often combined with a rear dormer.
Joist: A joist is one of the horizontal timber or steel members that support a floor or flat ceiling, spanning between walls or beams. Floorboards are fixed on top and ceilings below. Loft conversions usually need new, deeper floor joists, because existing ceiling joists are not designed to carry a room.
Lawful Development Certificate: A Lawful Development Certificate is a document from the council in England confirming that a proposed or existing use or building work is lawful, often because it is permitted development. Wales calls it a Certificate of Lawfulness; Scotland and Northern Ireland use a Certificate of Lawfulness of Proposed Use or Development.
Lintel: A lintel is a beam built into a wall above a window or door opening to carry the masonry above it. Modern lintels are usually galvanised steel or precast concrete, while older houses may have timber or stone lintels. A failing lintel often shows as cracking above the opening.
Listed building consent: Listed building consent is permission needed to demolish, alter or extend a listed building in any way that affects its character, inside or out. It applies across the UK, is separate from planning permission, and carrying out such work without consent is a criminal offence. Replacing windows or removing walls commonly needs it.
Load-bearing wall: A load-bearing wall is a wall that carries weight from above, such as floors, other walls or the roof, down to the foundations. Removing or altering one needs a structural engineer's design, temporary support during the work, and Building Regulations approval or, in Scotland, a building warrant.
LVT: LVT, or luxury vinyl tile, is a hard-wearing, water-resistant floor covering made in planks or tiles printed to look like wood or stone. It is warmer and quieter underfoot than ceramic tiles, suits kitchens and bathrooms, and needs a smooth, level subfloor, often prepared with plywood or levelling compound.
Mansard: A mansard is a roof, or a type of loft conversion, where the slope is rebuilt almost vertical, typically at around 70 degrees, with a flat or shallow top, creating a near full-height extra storey. Mansard loft conversions are common on city terraces and usually need planning permission.
Padstone: A padstone is a solid block of concrete, engineering brick or stone placed under each end of a beam to spread its load safely into the wall below. Its size and material are specified by the structural engineer, and building control usually inspects padstones before they are covered up.
Party wall: A party wall is a wall shared by two properties, such as the wall between semi-detached or terraced houses, or a wall standing across a boundary. In England and Wales, work to a party wall is covered by the Party Wall etc. Act 1996. Scotland and Northern Ireland have no equivalent Act.
Party wall award: A party wall award is a legal document drawn up by surveyors under the Party Wall etc. Act 1996, in England and Wales, when a neighbour does not consent to notifiable work. It sets out what work can be done, how and when, records the condition of the neighbour's property, and decides who pays the surveyors' costs.
Permeable paving: Permeable paving is a hard surface that lets rainwater soak through into the ground, such as permeable block paving, porous asphalt, resin-bound gravel on a permeable base or loose gravel. In England, front-garden surfaces over 5 square metres must be permeable or drain within the property, or they need planning permission.
Permitted development: Permitted development rights allow certain work to houses, such as some extensions, loft conversions and porches, without a planning application, provided the work meets set limits and conditions. Each UK nation sets its own rules. Rights are reduced for flats, listed buildings and conservation areas, and can be removed by planning conditions.
Planning permission: Planning permission is formal consent from your local planning authority, usually the council, to carry out building work or change how land or a building is used. Many smaller home improvements do not need it under permitted development rights, but the rules differ between England, Wales, Scotland and Northern Ireland.
Prior approval: Prior approval is a process in which the council checks specific matters, such as the effect on neighbours, before some types of permitted development go ahead. In England, it allows larger single-storey rear extensions, up to 6 m on semi-detached and terraced houses or 8 m on detached houses, without a full planning application.
Provisional sum: A provisional sum is an allowance in a quote for work that cannot be fully priced in advance, such as repairs that only show once a roof is stripped, or items you have not yet chosen. The final cost is adjusted up or down once the actual work or item is known.
Render beads: Render beads are metal or plastic profiles fixed to a wall before rendering to form straight, protected corners, edges and stop ends. A bellcast bead above the damp-proof course gives the render a neat drip edge and stops it bridging the DPC. Stop beads finish render cleanly against windows and other materials.
Repointing: Repointing is the process of raking out old, crumbling or loose mortar from the joints between bricks or stones and refilling them with fresh mortar. The new mortar should suit the wall: older solid walls usually need a softer lime mortar, as hard cement mortar can damage soft bricks.
Retention: A retention is part of the contract price held back from payment until a set point after completion, so that any defects found can be put right before it is released. Retentions are common on larger contracts; whether one applies, and how much it is, is agreed in the written contract.
Screed: A screed is a smooth, level layer of sand and cement or a flowing anhydrite mix laid over a concrete floor slab or insulation, ready for the final floor finish. Screeds often contain underfloor heating pipes, and they need time to dry before tiles, LVT or timber flooring can be laid.
Second fix: Second fix is the stage after plastering when visible fittings are installed and connected, such as sockets, switches, light fittings, radiators, sanitaryware, internal doors, skirting boards and architraves. Electrical and plumbing systems are then tested, and certificates are issued where required.
Skim coat: A skim coat is a thin layer of finishing plaster, typically 2 to 3 mm thick, trowelled over plasterboard or existing plaster to give a smooth surface ready for decoration. New skim usually needs several days or more to dry, followed by a diluted mist coat of paint before the main coats.
Snagging: Snagging is the process of checking finished work for small defects or incomplete items, such as paint marks, sticking doors, gaps in sealant or missing fittings, and listing them so they are put right. A snagging list is usually agreed near the end of a job, before final sign-off.
Soakaway: A soakaway is a pit or buried crate system, filled with rubble or plastic cells, that collects surface water from roofs or driveways and lets it soak gradually into the surrounding ground. It must sit far enough from buildings, usually at least 5 m, and suits ground that drains freely.
Soffit: A soffit is the board fixed underneath the overhang of a roof, between the fascia and the wall of the house, closing off the rafter ends. Soffits are usually uPVC or timber and may include vents that let air into the roof space to help reduce condensation.
Steel beam (RSJ): A steel beam, often called an RSJ (rolled steel joist), is a beam that carries the weight of walls, floors or roof above a new opening, such as where a load-bearing wall is removed. Its size is set by a structural engineer, it sits on padstones at each end, and it usually needs fire protection.
Structural engineer: A structural engineer is a qualified professional who works out the loads on a building and designs the beams, foundations and other elements needed to carry them safely. Their calculations and drawings are usually required by building control for wall removal, extensions, loft conversions and underpinning.
SuDS: SuDS, or sustainable drainage systems, are ways of managing rainwater close to where it falls, such as permeable paving, soakaways, rain gardens and green roofs, instead of piping it straight into sewers. They help reduce flooding and pollution. In Wales, larger new construction needs SuDS approval from the council.
Tanking: Tanking is waterproofing applied to walls and floors so water cannot pass through, used in showers, wet rooms and below-ground rooms such as basements. In bathrooms it is usually a liquid membrane or waterproof board system applied before tiling, with tapes sealing the joints and internal corners.
Trickle vent: A trickle vent is a small, adjustable vent, usually in the top of a window frame, that lets a steady, low level of fresh air into a room while the window is closed. Trickle vents help control condensation and are often required in new and replacement windows under Building Regulations.
U-value: A U-value measures how quickly heat passes through part of a building, such as a wall, roof, floor or window, in watts per square metre per degree of temperature difference (W/m²K). The lower the U-value, the better the insulation. Building Regulations set maximum U-values for new and replacement elements.
Underpinning: Underpinning is work to deepen or strengthen the foundations of an existing building, usually because of subsidence, poor ground or excavation nearby. It is carried out in short sections to a structural engineer's design and needs Building Regulations approval, or a building warrant in Scotland. In England and Wales, a party wall notice may be needed.
Variation: A variation is a change to the agreed work after a contract is signed, such as adding sockets, changing tiles or moving a wall. A variation should be agreed in writing before the work is done, with its effect on price and timescale, so both sides have a clear record.
Warm roof: A warm roof is a roof construction where the insulation sits above the roof deck or rafters, keeping the structure at roughly room temperature. It lowers the risk of condensation compared with a cold roof, where insulation sits between or below the joists with a ventilated gap above, and is common on new flat roofs.

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