Building Terms Glossary

Also: galleys.co.uk

UK temporary kitchen pod hire company offering self-contained kitchen units for delivery during renovations

Also: Gantt, bar chart schedule, programme bar chart

A visual project schedule showing tasks as horizontal bars plotted against a calendar timeline. The standard format for a construction programme — recommended by architects and builders for tracking extension builds.

Also: integral garage, attached garage, detached garage

A building for vehicle storage, either attached to or separate from the main house. Garages with foundations can trigger party wall obligations and count as neighbouring structures under Section 6.

Also: turf, lawn turf, rolls of turf, turf rolls

Rolled lawn grass supplied in sections for laying on prepared topsoil. Used for reinstating lawns destroyed by construction traffic. Cost: £2-7/m² material only, £10-20/m² supply and lay. Requires 100-150mm of prepared topsoil beneath.

Also: gas burner hob, gas cooktop

A hob that uses natural gas burners. Requires a Gas Safe registered engineer for connection and dedicated gas pipework to the hob position. Running cost approximately £74/year vs £190/year for induction at 2025 energy prices.

Also: Gas Safe certificate, gas work certificate, gas commissioning certificate, BS 6891 certificate

Compliance certificate issued by a Gas Safe registered engineer on completion of gas installation work (boiler, hob, gas connections). One of the regulated trade certificates building control requires before issuing the completion certificate.

Also: gas transporter, GDN, GNO, gas distribution network, Cadent, National Gas, SGN, Northern Gas Networks, Wales and West Utilities

The regional monopoly operator responsible for the gas supply pipe from the main to the meter. The only party legally permitted to move the supply pipe.

Also: Gas Safe compliance certificate, gas building regs notification

The compliance certificate issued via the Gas Safe Register when a registered gas engineer notifies a gas appliance installation, replacement, or disconnection. Gas Safe posts the certificate (Part L / Building Regulations notification) to the homeowner within ~14 days of the work being notified; it proves the installer was registered at the time and that the work was notified under the competent person scheme.

Also: gas fitter

Installs and services gas appliances including boilers, hobs, and gas fires

Also: gassaferegister.co.uk, Gas Safe

The official list of gas engineers legally permitted to carry out gas work in Great Britain. Homeowners must verify any gas engineer is registered before allowing gas work.

Legal requirements for gas work

Also: gas appliance certificate, Gas Safe commissioning certificate, boiler commissioning certificate

The certificate issued by a Gas Safe registered engineer confirming that gas appliances have been safely installed and commissioned. Required by building control where gas work forms part of the extension.

Also: 22mm gas pipe, steel gas pipe, copper gas pipe 22mm, domestic gas pipework

22mm copper or steel gas supply pipework for domestic boiler and hob connections. Push-fit plastic is prohibited for gas. A 1m copper run is mandatory at the boiler connection.

Also: geotextile, filter membrane, drainage membrane, nonwoven geotextile, filter fabric

A permeable fabric material that filters water while blocking soil particles. In soakaway construction, geotextile wraps around soakaway crates to allow water to permeate out while preventing soil fines from entering and gradually clogging the void space. Also used in French drains and as a separation layer under hardcore. Without geotextile, a soakaway will progressively lose capacity as soil infiltrates the crates.

Specialist drill bits with spear-point carbide tips designed for drilling through ceramic tiles, porcelain, and glass without cracking. Used for fixing towel rails, shelves, and accessories to tiled walls. Always drill at low speed with water cooling.

Also: roof glazing, rooflights, roof windows, glazed roof units

Roof glazing materials — off-the-shelf Velux-style pitched roof windows and bespoke large-format aluminium rooflights. The choice has major cost, lead-time, and installation implications that shape the roofing sequence.

Also: oil-based gloss, water-based gloss, satinwood paint, eggshell paint, wood finish paint

Woodwork paint used for skirting boards, architrave, door frames, and window boards in a UK extension. Available in high-sheen (gloss) and mid-sheen (satinwood/eggshell) finishes. Typically applied over a primer coat with two topcoats for a durable, cleanable finish on painted timber.

Also: Gripfill, panel adhesive, No More Nails

High-tack construction adhesive for fixing skirting, architrave, and trim to walls. Common brands include Gripfill and No More Nails. Always combine with mechanical fixings for a secure bond.

Also: grab hire, grab truck, grab lorry hire, 8-wheel grab lorry

A tipper lorry fitted with a hydraulic grab arm that scoops bulk waste (earth, rubble, hardcore) without manual loading, carrying 16-18 tonnes per load

Also: grab hire company, grab lorry contractor

Specialist waste removal service using 8-wheeled tipper lorries with hydraulic grab arms for bulk removal of earth, rubble, and hardcore

Also: wood grain direction, planing direction, with the grain, against the grain

The orientation of wood fibres in timber, which governs planer and hand plane technique. Planing against the grain causes tearout — lifted and torn wood fibres — regardless of blade sharpness or depth setting. Planing with the grain produces a clean surface. A fundamental woodworking concept that homeowners must understand before using a planer on doors or timber surfaces.

Also: natural stone worktop, granite slab worktop, natural granite worktop, granite stone worktop

Natural stone worktop with unique patterns. £250-600/lm installed. Requires professional templating after units are fitted. Needs annual sealing. Each slab is unique in colour and veining.

Also: graphite EPS, grey polystyrene, enhanced EPS

Graphite-enhanced expanded polystyrene achieving lambda 0.030 W/mK vs 0.038 W/mK for standard white EPS. Provides 20-25% thickness saving at a small cost premium.

Also: grid module switch, grid switching plate, modular grid switch

A modular wiring system where individual switch modules can be combined into a single plate using a carrier frame. Preferred for kitchen islands where multiple appliances require accessible local isolation on a single splashback plate.

Excavates foundations, lays drainage, and prepares the site for building

Also: tile grout, wall grout, floor grout

Cement-based filler applied between tiles after the adhesive has set. Available in various colours to complement tile choice. Floor grout should be a flexible formulation. Epoxy grout is more expensive but stain-resistant, best suited for tiled worktops. Use silicone (not grout) at internal corners and perimeter junctions.

Also: rubber grout float, tile grout float, grouting float

A rubber-faced flat tool used to press grout into tile joints and wipe off the excess. Essential finishing tool for every tiling job.

Also: fibreglass edge trim, GRP drip trim, aluminium GRP trim, flat roof edge trim, starter trim

Also: fibreglass roof, GRP roof, glass reinforced polyester, fibreglass flat roof, GRP flat roof system, Cure It, CrysticROOF

Glass-reinforced polyester flat roof system applied as a liquid resin and glass fibre matting that cures to form a seamless, rigid, waterproof surface. Very durable (25+ years) but more skill-intensive to apply than EPDM. Best installed by a specialist.

Also: fibreglass resin, roofing resin, GRP laminating resin, LSE resin, low-styrene resin

Also: fibreglass roofer, GRP installer, approved GRP installer, flat roof GRP contractor

Also: fibreglass topcoat, GRP gelcoat, roofing topcoat, GRP finishing coat

Also: router guide bush, template guide, guide collar, template bush

A collar fitted to the router base that runs along a template or jig to constrain the cut path. Understanding guide bushes is essential for using the Trend hinge jig (requires 30mm OD guide bush) and worktop jigs (typically requires 30mm guide bush) — using the wrong size creates a dimensional offset that compounds across the joint. Appears in 4 of 11 community threads as a source of real errors.