Building Terms Glossary

Also: screed laitance, calcium sulphate laitance

Weak powdery surface layer that forms on anhydrite screeds during curing. Must be mechanically sanded off 5-7 days after pour before any adhesive or flooring is applied.

Also: thermal conductivity, lambda, W/mK value

Thermal conductivity of an insulation material measured in W/mK. Lower lambda means better insulation per mm. Standard PIR achieves 0.022 W/mK; mineral wool 0.035-0.044 W/mK; EPS 0.030-0.038 W/mK.

Also: laminate floor, laminate boards, click laminate, AC rating laminate

A budget floor covering with a printed wood/stone image over HDF. Not recommended for kitchens due to moisture sensitivity at joints. Also impedes UFH efficiency. Frequently confused with LVT or engineered wood by homeowners.

Also: laminate kitchen worktop, Formica worktop, compact laminate worktop, postform worktop

Most affordable worktop option (£80-200/lm supply-only). Chipboard core with decorative laminate surface. Huge design range, easy to fit, but not heat-resistant and joiners are visible. Compact laminate variant enables undermount sinks.

Also: HM Land Registry, gov.uk/land-registry, HMLR

Government organisation registering land and property ownership in England and Wales; used to verify adjoining ownership before serving party wall notices

Also: topographic surveyor, setting-out surveyor, site surveyor

Specialist who establishes benchmark pegs and datum marks on site. Can be hired to set levels at the start of groundworks for £250-540, a viable alternative for homeowners without a second person to operate an optical level.

Also: landfill levy

UK government levy on waste disposed of in landfill, currently over £130 per tonne, a major driver of skip hire pricing

Plans showing proposed planting, paving, and external works. Often required as a planning condition to be formally discharged before or during construction.

Also: landscape gardener, garden designer

Trade responsible for garden reinstatement after construction, including patio laying, planting, and aesthetic external finishes.

Also: larger home extension, neighbour consultation scheme for larger extensions

A permitted development provision allowing single-storey rear extensions beyond standard PD depth limits (up to 6m for semi-detached/terraced or 8m for detached) subject to a neighbour consultation (prior approval) process.

Also: laser receiver, laser line detector, laser sensor

An accessory that detects a laser beam electronically, extending the usable range of a cross-line laser level from 10-30m to 50m+ outdoors where the beam is invisible in daylight.

Also: cross-line laser level, self-levelling laser level, line laser level, 2-axis laser level

A device that projects visible laser lines (horizontal, vertical, or both) onto walls and floors. Invaluable for setting kitchen unit heights, aligning tiles, marking picture rails, and checking floor levels across a room. Self-levelling models are easiest to use.

Also: laser rangefinder, electronic tape measure, laser distance measurer

Laser distance measurer for quick, accurate room and site measurements

A document confirming that work or use is lawful under planning law

Also: lead grade, lead code number, Code 3 lead, Code 4 lead, Code 5 lead, lead colour code, BS EN 12588 lead code

Also: dresser tool, lead dressing tool, bossing stick

Also: code 3 lead, code 4 lead, lead sheet, flashing lead, rolled lead sheet, lead soakers

Sheet lead used to weatherproof junctions between the roof and walls, around chimneys, and at abutments. Code 3 (1.32mm) for simple flashings; Code 4 (1.80mm) for gutters, valleys and areas subject to more movement. Expensive but the only material that reliably lasts the lifetime of the roof.

Also: lead-based paint, lead paint in old houses, white lead paint

Paint containing lead pigment, widely used in UK domestic properties until the 1970s and in limited specialist uses until the early 1990s. Properties built before 1970 should be treated as likely to contain lead paint. Lead paint in good condition is best left sealed; removal by heat or sanding is the key exposure pathway. Governed by CLAW Regulations 2002. Properties 1970–1992 are moderate risk requiring a test; post-1992 are negligible risk.

Also: LSA, LSTA, Lead Sheet Training Academy, leadsheet.co.uk

Also: soaker, soakers, lead soakers, tile soaker

Also: lead worker, lead plumber, lead roofing specialist, sheet lead specialist

Specialist trade for forming lead flashings around roof windows, chimneys, and abutments. Distinct from a roofer — roofers tile, lead specialists form flashings. LSTA (Lead Sheet Training Academy) certified. On Ian's build Craig Littlechild was engaged separately from roofer Aiden for all lead work.

Also: manufacturing lead time, delivery lead time, order lead time

Time between placing an order and delivery/installation. Standard aluminium windows: 8-12 weeks; premium systems: 10-16 weeks. The most common cause of project delays.

Also: lead alternative flashing, Wakaflex, Ubiflex, Ubiflex B3, Ubiflex Extreme, Alto Lead, Alcan flashing, lead substitute, flexible flashing strip

Also: recessed downlight, recessed LED fitting, ceiling downlight, fire-rated downlight, IP65 downlight

The dominant ceiling lighting fitting for kitchen extensions, recessed into plasterboard. Fire-rated versions required where the ceiling is beneath a bedroom or bathroom. Typical extensions specify 20-29 downlights.

Also: LED dimmer flicker, trailing edge dimmer, leading edge dimmer, dimmer minimum load

Not all dimmer switches work with all LED bulbs — mismatches cause flickering, buzzing, and premature failure. Must be specified at second fix by confirming trailing-edge dimmer type with LED lamp requirements.

Also: Legionella, legionellosis, Legionnaires disease risk, hot water Legionella

NHBC Standards require hot water temperature at any outlet to reach at least 50°C within 1 minute of running. Below this temperature Legionella bacteria can multiply. A commissioning hold point: the plumber must verify and document flow temperatures at handover.

Also: LBA, letter before claim, pre-action letter, letter of claim

A formal written letter sent before issuing court proceedings, setting out the nature of the claim, the remedy sought, and a deadline (typically 14 days) for the other party to respond. Courts expect a letter before action to have been sent before a claim is filed.

Also: surveying staff, levelling rod, staff rod, E-staff, telescopic staff

A graduated measuring rod held vertically on the point being measured while the observer reads the value through an optical level's eyepiece. The optical level cannot produce any readings without it.

Also: interior lighting designer

A specialist who produces a task-specific lighting layout plan that the electrician then executes. Distinct from an electrician. A professional concept plan costs around £1,500 but prevents the grid-based downlight layouts that electricians default to without guidance.

Also: lighting circuit zone, dimmer zone, lighting scene

The division of a room's lighting into separately switchable and dimmable circuits — e.g. ambient downlights, task lighting, under-cabinet LEDs, and island pendants as separate zones.

Also: limitation, time limit for claims, statute of limitations, six-year limitation

The legal time limit within which a civil claim must be brought. For breach of contract: 6 years. The Building Safety Act 2022 extended limitation periods for dwellings: 30 years retrospectively for pre-June 2022 completions, 15 years for post-June 2022.

Also: bricklayers line pins, steel line pins

Steel pins pushed into mortar joints to hold a builder's line taut between courses

Also: lintels, door lintel, window lintel

A horizontal structural element placed above openings (doors, windows) to transfer the load from above to the sides. Can be concrete, steel, or stone. Building control inspects that lintels are correctly sized and installed over every opening.

Also: tile lippage, tile height difference, tile edge height variation

The height difference between adjacent tile edges. The most common tiling quality complaint, especially with large-format rectified tiles. Controlled by substrate flatness and tile levelling systems.

Also: anhydrite screed, calcium sulphate screed, flow screed, liquid screed, Gyvlon, Gypsol, Cemfloor, Longfloor

Pumpable self-levelling calcium sulphate screed. Nearly twice the thermal conductivity of sand-cement. Preferred for UFH. Requires laitance removal. Not suitable for wet rooms.

Also: LADs, liquidated and ascertained damages, delay damages

A pre-agreed amount written into your contract that the builder pays you for each week they overrun, typically a fixed sum per day or week. It avoids arguments about how much a delay has actually cost you.

Also: winding up, compulsory liquidation, creditors voluntary liquidation, CVL, going into liquidation

The formal process of winding up a company and selling its assets to pay creditors. Once a builder enters liquidation, the company will cease to exist and recovering your money becomes very unlikely.

Also: Grade I listed, Grade II listed, Grade II* listed

A building of special architectural or historic interest, designated at Grade I, Grade II*, or Grade II. Any external alteration requires both planning permission and listed building consent, removing permitted development rights.

Also: LBC

A separate consent required (in addition to planning permission) for any works to a listed building that affect its character as a building of special architectural or historic interest. Applies to all listed grades (I, II*, II).

A wall that supports weight from floors, roofs, or other walls above

Also: LGO, LGSCO, Planning Ombudsman

The body that investigates complaints about how a council handled a planning application, but cannot overturn planning decisions.

Also: appliance isolation, means of isolation, local isolator

BS 7671 Reg 462.2 requires every fixed appliance to have a means of local isolation operable without reaching over or around the appliance, affecting socket layout for under-worktop appliances.

Also: local development plan, development plan

The council's statutory development plan document that sets out local planning policies. Planning decisions and appeals must be determined in accordance with the local plan unless material considerations indicate otherwise.

Also: LPA, council planning department

The council department responsible for determining planning applications, enforcing planning law, and maintaining the public planning register. Every local authority in England has one.

Also: loft stilts, insulation spacer legs, loft storage legs

Plastic or metal stilts enabling loft storage boards to sit above mineral wool insulation without compressing it. Standard solution to the compression problem in lofts.

Also: right to light, daylight impact

A material planning consideration where a proposed development reduces the natural light reaching a neighbouring property's windows or rooms.

Also: view obstruction, blocked view

Explicitly a non-material planning consideration — loss of view cannot be used as grounds to refuse planning permission.

Also: finishing nails, lost head pins

Finishing nails (38-50mm) with a small head designed to be punched below the timber surface and filled. Standard mechanical fixing for skirting board and architrave.

Also: gap-filling foam, minimal expansion foam

Foam sealant for filling gaps between PIR insulation boards. Must be low-expansion type — standard expanding foam displaces adjacent boards and creates thermal bridges.

Also: low-tack tape, snagging tape, delicate surface tape, yellow frog tape

Adhesive tape with reduced tack that can be applied to freshly painted surfaces and delicate finishes without damage. Used during snagging inspections to mark the location of each defect so the builder can find it easily during remediation, and for two-tone paint lines where a sharper edge is needed than standard masking tape can deliver.

Also: Type LR underlay, Type HR underlay, high resistance underlay, low resistance underlay, HR felt, LR felt, vapour permeable classification, vapour impermeable underlay

Also: Lines Search Before You Dig, lsbud.co.uk, utility search before digging, line search

Free service for domestic users to identify underground utility assets before any groundworks or trench digging. Covers 160+ asset owners and 2 million km of assets.

Also: Linesearch Before U Dig, lsbud.co.uk

Free online service for identifying underground gas, electricity, water, and telecoms assets before excavation. Covers 160+ asset owners.

Also: LSOH cable, low smoke zero halogen, low smoke halogen free, 6242B cable, LSZH twin and earth

Low Smoke Zero Halogen cable (product code 6242B, white sheath) that emits minimal smoke and no halogen acids in fire. Not legally required for standard domestic extensions but may be specified for HMOs, escape routes, or multi-occupancy buildings.

Also: LVT, luxury vinyl plank, LVP, click LVT, glue-down LVT, looselay LVT, rigid core LVT, SPC flooring, vinyl plank flooring

A tile or plank format floor covering with a durable wear layer. Three installation formats: click, glue-down, and looselay. Increasingly popular for kitchen extensions — warm underfoot, water-resistant, and compatible with UFH. Glue-down format preferred in south-facing extensions with large glazing for thermal stability.

Also: vinyl floor adhesive, glue-down LVT adhesive, wet-set adhesive, pressure-sensitive adhesive, hard-set adhesive

Specialist adhesive for glue-down LVT. Two types: wet-set (hard-set, permanent bond) and pressure-sensitive (PS, allows repositioning). In south-facing extensions with large glazing, wet-set adhesive is required to prevent LVT shrinkage from direct sunlight. Not interchangeable with tile adhesive.