MEP Snagging Checklist: Mechanical, Electrical and Plumbing

This checklist covers the mechanical, electrical and plumbing (MEP) items most likely to fail snagging on a UK new build: sockets, consumer units, extractor fans, boilers, hot water safety and drainage. For a single plot, allow 45 to 60 minutes to work through it properly, longer if you're testing every socket and tap.

MEP items hide the most expensive defects on any plot. A cracked tile is a five-minute fix. A miswired consumer unit, an unlimited bath temperature, or an unducted kitchen extractor is a compliance issue that can hold up completion or cause harm after handover. This checklist is built around the areas that UK Building Regulations and NHBC Standards specifically call out, so you're checking against a known standard, not just a gut feel.

If you're snagging a whole plot, pair this with our new-build snagging checklist, room by room for finishes, joinery and decoration, which this page deliberately leaves out.

Electrical: consumer unit and circuits

• Consumer unit is made from non-combustible material (metal, not plastic) and every circuit is labelled clearly, matching the circuit schedule.
• MCBs and RCDs trip and reset cleanly when tested (this is a visual and function check, not a substitute for the electrician's test certificate).
• Electrical Installation Certificate (EIC) is on site or referenced in the handover pack for any new circuit work. For notifiable work, keep the Building Regulations compliance certificate too.
• Main bonding is visible and connected to gas, water and any other services entering the building where required.

Electrical: sockets, switches and lighting

• Kitchens and living rooms have at least eight socket outlets; main bedrooms have at least six, matching the NHBC guidance for new homes. The standards set out minimum numbers of socket outlets for each room, for instance, at least eight in kitchens and living rooms, and six in the main bedroom.
• Sockets and switches sit between 450mm and 1200mm from floor level, with none inside bathroom splash zones. The position of sockets and switches must also be considered and outlets should typically be 450 - 1200mm above floor level in new dwellings, and kept clear of splash zones and heat sources.
• Cable routes follow safe zones (vertical or horizontal from an outlet, at least 50mm from the wall face or joist edge) so a future screw or drill bit won't hit a live cable. Cables without special protection should be positioned vertically or horizontally from the outlet or switch they serve. They should be at least 50mm from the surface of a wall, or 50mm from the top or bottom of joists in floors or ceilings.
• The cooking area has a dedicated supply of at least 30A, properly switched and terminated. Areas designed for cooking need a minimum 30A supply that's suitably switched and terminated.
• No sockets, fittings or cables sit within 600mm of a bath or shower unless they're rated for that zone. Anything else mounted within 600 mm of the bath or shower is notifiable.
• Every switch operates the correct light, every socket is live (test with a plug-in tester), and no reversed polarity is found.
• Smoke and heat alarms are mains-powered and interlinked throughout the property. Mains-powered, interconnected smoke and heat alarms are required throughout.
• External lights, PIR sensors and any garage or outbuilding circuits are tested and switch correctly.

Heating and hot water

• Boiler has a visible commissioning record or benchmark log filled in by the installer, not left blank.
• Hot water at bath taps does not exceed 48°C (check with a thermometer or ask for the TMV commissioning record). Part G requires that the hot water temperature at bath outlets is limited to a maximum of 48°C.
• Unvented cylinders have a temperature and pressure relief valve, expansion vessel and a discharge pipe routed safely to outside. Unvented systems must include temperature and pressure relief valves, expansion vessels, and discharge pipes for safe pressure release.
• Hot taps are fitted on the left, cold on the right, in every room.
• Radiators heat evenly across the whole panel, with no cold spots that suggest trapped air or an unbalanced system.
• Thermostatic radiator valves (TRVs) turn smoothly and the room thermostat and programmer are labelled and functioning.
• No visible leaks, drips or staining around the boiler, cylinder, radiator valves or pipe joints.

Plumbing and sanitary

• Every dwelling has at least one WC, one washbasin next to it, and a bath or shower with both hot and cold supply. Every dwelling must have access to a WC with adequate flushing mechanism, a washbasin adjacent to the WC, and either a bath or shower with hot and cold water supply.
• WCs use a dual-flush cistern (typically 6/4 litre) as part of the water efficiency target for new homes. A WC with adequate flushing mechanism, dual flush (6L/4L or 4L/2.6L) is the water efficiency standard for new build.
• Taps run clear within a few seconds, with no spluttering that suggests trapped air in the system.
• Waste pipes under sinks, baths and showers are solvent-welded or push-fit correctly, with no gaps or weeping joints.
• Shower trays and baths are sealed to the wall with a continuous bead, no gaps where water could track behind.
• Washing machine and dishwasher connection points are capped, in place and leak-free.
• External gullies and manhole covers are clear, correctly seated and not cracked.
• Stopcock is accessible, clearly labelled, and actually shuts off the water supply when tested.

Ventilation

• Kitchen extractor achieves the required rate: 30 l/s if mounted above the hob as a cooker hood, or 60 l/s if positioned elsewhere in the room. Building Regulations Approved Document F requires kitchen extract fans to achieve minimum 30 l/s adjacent to a hob. Cooker hoods must be capable of achieving a minimum of 60 l/s for intermittent operation.
• Bathroom and en-suite extractors achieve at least 15 l/s intermittent, positioned high in the room, away from the door. Bathrooms with toilets require 15 litres per second intermittent extract. Part F requires extract fans to be positioned as high as practicable in the room and as far as possible from the main source of replacement air.
• Separate WCs extract at least 6 l/s, and utility rooms at least 30 l/s intermittent. Separate WCs require 6 litres per second intermittent or 6 l/s continuous. Utility rooms require 30 litres per second intermittent extract or 8 l/s continuous with boost to 30 l/s.
• Kitchen and cooker hood ducting terminates outside through a weatherproof grille, never recirculating back into the room where ducting to outside is required. All extraction must either duct to outside or use a recirculation filter, but recirculation does not comply with Part F's ventilation requirements for moisture removal.
• Extract fans have a commissioning record confirming they meet their rated airflow, as this is now a legal requirement for the installer. The 2022 updates to ADF made it a legal requirement for the installer to test and commission the installed fan to prove that it is meeting the required airflow rates.
• Trickle vents are fitted in window frames where specified and open and close freely.
• MVHR units (where fitted) have a handover record confirming filters are clean and airflow has been balanced.

What to do with the findings

Group everything by trade before you send a report out. A single list mixing electrical, plumbing and ventilation issues is harder for a site manager to action than three short lists, one per trade.

Flag anything safety-related (bath temperature over 48°C, exposed live cable, unlimited extract rate) separately and ask for it to be closed out before handover, not left on a snag list for later. These aren't cosmetic items and most won't be covered once the NHBC builder warranty period ends. During the builder warranty period, the builder must put right, at their own expense, any defect or damage caused by the builder's failure to meet the NHBC's technical requirements.

Photograph each defect in place, including the room and any relevant label or meter reading (consumer unit circuit label, airflow meter if you have one, thermometer reading on the bath tap). If you're using Snag.ai, photographing the defect is enough: it logs the snag, writes a description, tags the trade and severity, and picks up any other snags visible in the same shot. You can then export the whole list as a client-ready Word report at the end of the visit, grouped and ready to send.

If you're deciding between a checklist on paper and an app for this kind of work, our guide on snagging app vs spreadsheet covers what actually changes on site when you switch.