For small builders and main contractors (England)
Last reviewed: March 2026
Here's what the jargon means, in one line each. Then you can get back to work.
AD (Approved Document) - Government guidance that shows one way to comply with a specific Part of the Building Regs; not law, but what BC usually work from.
Airtightness test - Pressure test on a new building to measure how leaky it is; the result feeds straight into SAP and Part L sign-off.
BR 211 - The radon guidance document that tells you when you need radon barriers/sumps and how to detail them.
BS 7671 - Wiring Regulations; the standard electricians follow for safe electrical installations (used to show Part P compliance).
Building notice - Quick-start Building Regs application with no formal plans approval; BC sort compliance on site as you go.
Cavity barrier - Fire-stopping piece in a cavity (wall/roof) that stops flames and smoke racing through gaps.
CE/UKCA marking - Manufacturer mark showing a product meets relevant EU/UK standards and is suitable for the claimed use.
CIS (Construction Industry Scheme) - HMRC system for taxing subcontractor payments at source; you verify subs and deduct/tax correctly.
Completion certificate - Letter from Building Control saying, as far as they're concerned, the finished work complies with the Building Regs.
Competent Person Scheme - Self-cert route where registered installers (Gas Safe, NICEIC, FENSA etc.) can notify certain work without a separate BC application.
Consumer unit - Modern fuse board with MCBs and RCD/RCBOs, normally at the heart of the domestic electrical installation.
CPD (Continuing Professional Development) - Ongoing training/learning to stay on top of regs, standards and best practice.
DPC (Damp-proof course) - Layer in walls (usually 150 mm above ground) that stops rising damp from the ground.
DPM (Damp-proof membrane) - Sheet under floors or in walls that stops moisture coming up through slabs or in from the ground.
EIC (Electrical Installation Certificate) - Formal test certificate for new circuits or full installs, proving it's been tested to BS 7671.
EPC (Energy Performance Certificate) - Band A-G energy rating for a dwelling, based on SAP; needed at sale/let and driven by Part L.
FD20/FD30 - Fire door that holds back fire for around 20 or 30 minutes in test conditions, including its frame, seals and hardware.
Fire stopping - Materials and methods used to seal gaps/penetrations in fire-resisting elements so fire and smoke can't bypass walls/floors.
Flue - The pipe/duct that carries combustion gases from an appliance to outside safely.
Free area (vent/opening) - Actual open area of a vent or open window (not frame size) used to prove ventilation and Part O cooling.
Full plans application - Building Regs route where you submit drawings/calcs, get formal plans approval, then build to that design.
Gas Safe - Official UK gas engineer register; if someone's fitting gas boilers/fires, they should be on it.
Going (stair) - The horizontal depth of one stair tread, measured nosing to nosing; used with rise to set stair pitch.
Guarding - Barrier/balustrade that stops people falling off the edge of stairs, landings, balconies and drops.
HETAS - Registration body for solid fuel/biomass stove installers who can self-certify many solid-fuel installs.
Intumescent strip - Heat-activated strip around fire doors/frames that swells in a fire to seal the gap and block smoke/flame.
LABC (Local Authority Building Control) - Collective banner for council Building Control teams, plus their central guidance body.
LACORS - Fire safety guidance used by councils for HMOs; often treated as the standard alongside Part B, even though it's "only" guidance.
Limiting U-value - Worst-case (highest) U-value you're allowed for a wall/roof/floor/window before you fail Part L.
MEV / dMEV - Mechanical extract ventilation: MEV = central fan with ducts, dMEV = individual continuous fans in rooms.
Minor Works certificate - Short electrical certificate for small jobs (like altering existing circuits) where a full EIC isn't needed.
MVHR (Mechanical Ventilation with Heat Recovery) - Whole-house system that extracts stale air, supplies fresh air, and recovers heat between the two.
Notifiable work (electrical) - Electrical jobs that must be notified under Part P (e.g. new circuits, consumer unit changes, most full rewires).
OFTEC - Registration body for oil-fired heating engineers and some oil tank installers.
PAS 24 - Security test standard for doors/windows; meeting it is the usual way to show compliance with Part Q on new dwellings.
Pitch (stair) - Angle of the stair; too steep and you'll fail Part K (domestic max around 42°).
Purge ventilation - Short-term high-rate ventilation (usually by opening windows/doors) used to clear heat/smells/fumes.
Radon - Naturally occurring radioactive gas from the ground; in higher-risk areas you need radon barriers/sumps under Part C.
RCD / RCBO - Safety devices that trip quickly on earth leakage; RCBO combines RCD and MCB in one unit.
Regularisation - Retrospective Building Control process to legalise past unauthorised work; usually involves higher fees and opening up.
Resilient bar - Thin steel channel fixed to framing so plasterboard "floats", reducing sound transmission.
Rise (stair) - The vertical height from one stair nosing to the next; must be consistent and within Part K limits.
Robust Details - Pre-approved separating wall/floor designs that, if built exactly, can avoid sound testing for Part E.
SAP (Standard Assessment Procedure) - The calculation method used to assess energy performance and produce EPCs for dwellings.
Separating wall/floor - Wall or floor between different dwellings (or rooms in an HMO) that must meet higher fire and sound standards.
Smoke seal - Flexible strip (often with intumescent) on door edges that stops smoke passing in a fire.
Soakaway - Underground construction (often rubble or crate system) that lets rainwater drain into the ground instead of a sewer.
Sound testing - On-site test of separating walls/floors to prove they meet Part E airborne/impact noise standards.
Thermal bridge - Part of the building where heat leaks faster (e.g. around junctions, steel) and can cause cold spots and condensation.
TMV (Thermostatic Mixing Valve) - Valve that mixes hot and cold to a safe outlet temperature to prevent scalding (e.g. baths).
TPR valve (Temperature/Pressure Relief valve) - Safety valve on cylinders that opens if temperature or pressure gets too high.
Trickle vent - Small controllable background vent, usually in a window frame, used to meet Part F background ventilation.
Tundish - Visible fitting on discharge pipes (usually from unvented cylinders) that lets you see if the valve is dripping or discharging.
U-value - Measure of heat loss through a building element (W/m²K); lower number = better insulation.
Unvented cylinder - Mains-pressure hot water cylinder with safety valves and expansion gear instead of a header tank; tightly controlled under Part G.
Here's what it means. Now get back to work.
This page is a general reference for small builders and main contractors working on dwellings in England. It doesn't cover every term or non-domestic scenario. Always check the latest Approved Documents, your drawings/spec, planning conditions and Building Control before you start cutting or pouring. SiteKiln does not provide legal, financial or tax advice. All content is for general information purposes only. Always seek professional advice for your specific situation.
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Working in Wales? The building rules are different. See our Working in Wales guides.
Working in Scotland? Building standards work differently. See our Working in Scotland guides.
Working in Northern Ireland? The system uses Technical Booklets. See our Working in Northern Ireland guides.
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