New Build Snagging: Plumbing and Heating Checklist for London New Build Buyers
Plumbing and heating defects are among the most common snagging issues in London new build properties. This checklist tells new build buyers exactly what to inspect before legal completion and during the defects liability period.
Why Plumbing Snagging Matters in London New Builds
New build properties in London are covered by a 10-year structural warranty — typically provided by NHBC Buildmark or a similar scheme — and a two-year builder defects liability period during which the developer is obliged to rectify defects that arise from poor workmanship or materials. However, the defects liability period only covers defects that are reported to the developer. Any plumbing or heating issue that goes undetected and unreported within the two-year window will fall outside the developer liability, and the cost of repair will fall on the homeowner.
Identifying plumbing defects at snagging — the inspection process before or shortly after legal completion — ensures that issues are recorded and reported while the developer is legally obligated to fix them. A professional snagging survey by an independent inspector will typically identify 30 to 150 defects in a London new build, of which a significant proportion will be plumbing and heating related.
Before Legal Completion: What to Check
Before exchanging contracts or completing on a new build, request a pre-completion snagging inspection. The developer has the right to refuse access before exchange, but many developers will allow an inspection once contracts are exchanged. At the pre-completion inspection, check every tap and shower for correct flow, test the heating by running it for at least 30 minutes and checking that all radiators reach temperature, run water in the kitchen and bathrooms and check under all sink cabinets and vanity units for leaks at the trap and supply connections, and flush every toilet at least twice to check that the cistern fills and flushes correctly.
Check that the boiler fires and that the pressure gauge is within the correct operating range. Ask the developer for the boiler user manual, the boiler registration documentation confirming the Benchmark commissioning record has been completed, and the warranty documents. A boiler that has not been Benchmark-commissioned will not have a valid manufacturer warranty — this is a defect that must be addressed before completion.
Plumbing Defects Commonly Found in London New Builds
The most frequently reported plumbing defects in London new builds include: inadequate water pressure at upper floor taps and showers; leaking push-fit or compression fittings under kitchen and bathroom units concealed by cabinetry; incorrect gradient on waste pipes causing slow drainage or gurgling; missing or incorrectly fitted access panels to concealed pipework; boiler flue terminating too close to windows or ventilation openings; and hot water cylinders where the thermostat is set incorrectly, producing water that is not hot enough to prevent Legionella.
Shower trays that retain standing water indicate incorrect fall towards the drain — a builder defect that is straightforward to fix during the snagging period but requires removing and resetting the tray if left until later. Extractor fans in bathrooms that are not connected to the ductwork — a common London new build defect — allow moisture to accumulate and cause mould in the ceiling void rather than venting outside.
The Heating System Commissioning Record
Every new build heating system in the UK must be commissioned and the Benchmark commissioning record completed by a Gas Safe registered engineer before the property is occupied. The Benchmark document records the boiler settings, system pressure, expansion vessel pre-charge pressure, inhibitor concentration, and the results of flue gas analysis at commissioning. Ask the developer to produce the completed Benchmark document at snagging. If it has not been completed, the manufacturer warranty on the boiler is void from day one, and the developer must arrange for the commissioning to be completed and the record provided.
During the Two-Year Defects Liability Period
During the first two years in a London new build, report every plumbing defect to the developer in writing and keep a record of all reports and responses. Defects that are intermittent — a radiator that occasionally fails to heat, a tap that occasionally drips — should be documented with photographs and logged in writing even if the problem is not immediately apparent at the time the developer attends. Prestige Engineers carry out independent plumbing and heating snagging surveys for London new build buyers, providing written reports that can be submitted to developers as formal defect records.