Does NHBC Warranty Cover Plumbing? Years, Exclusions, Claims

The NHBC Buildmark warranty does cover plumbing, but only during the first two years after completion, and only when the problem stems from the builder failing to meet NHBC’s standards. From year three onward, internal plumbing and heating pipework fall outside the policy entirely. Underground drainage is the one plumbing-adjacent element that stays covered for the full ten years.¹

Why the Answer Depends on the Year

Buildmark is structured in sections that cover different periods and different kinds of problem. Section 2 runs for the first two years and is a builder warranty: the builder must fix any defect caused by a failure to meet NHBC requirements, and NHBC guarantees that obligation. Section 3 runs from year three to year ten and is an insurance policy, but it only pays out for damage caused by defects in specific structural parts of the home.² Plumbing sits comfortably inside Section 2 and sits outside Section 3. That single split explains most of the confusion homeowners run into.

The premium is paid by the builder, so there is no cost to you for the cover itself.³

Plumbing Cover in Years One and Two

During the builder warranty period, plumbing and drainage defects are covered when they result from the builder failing to meet NHBC requirements.⁴ In practical terms, that means the builder must have complied with Building Regulations and used workmanship and materials fit for purpose.⁵

The policy definition of the “home” during this period takes in the heating system, electrical wiring, and any other mechanical and electrical equipment needed to meet Building Regulations, as long as it was newly installed by the builder and serves your home only.⁵ A leaking pipe joint, a faulty radiator connection, water pressure problems caused by poor installation, or a drainage defect from substandard workmanship are all the builder’s responsibility.

NHBC’s technical standards, set out in Chapter 8.1, give concrete numbers for what counts as acceptable. Cold water needs a minimum dynamic pressure of 1.5 bar at the internal stop valve and a flow rate of at least 20 litres per minute. Hot water must reach 50°C within one minute at any outlet. Pipework must be corrosion-resistant, insulated in unheated spaces, and capable of being fully drained.⁶ Fall short of any of these, and it’s a defect the builder must put right.

What Happens From Year Three Onward

Once Section 3 takes over, cover is limited to damage caused by defects in listed structural parts: foundations, load-bearing walls, roof structures, floors, staircases, and retaining walls. Internal plumbing, heating pipework, and boilers are mechanical components, not structural ones, and they are not covered.⁴ The Financial Ombudsman Service has upheld that reading, finding NHBC acted fairly when it declined a water-leak claim under Section 3 because internal plumbing is not among the listed structural parts.⁷

Underground drainage is the exception. The 2025 policy booklet confirms that newly constructed underground drainage systems serving the home, including associated pipes, channels, gullies, and inspection chambers, remain covered under Section 3 where the builder installed them and you are legally responsible for them.⁸ A separate FOS decision found NHBC was wrong to deny an underground drainage claim on the basis that the pipes were still functional, ruling that bellied pipework and damaged benching counted as physical damage.⁹ All Section 3 claims also have to meet a minimum claim value set out in the policy documents.

Exclusions That Apply Even in the First Two Years

Being inside Section 2 is not an automatic yes. The policy carves out several things:

The incoming mains water supply pipe is not part of the covered “home.”⁵
Problems caused by wear and tear, neglect, or lack of maintenance are excluded.¹
Heating or hot water systems shared with other homes are excluded.⁸
Boilers and domestic goods sit under the manufacturer’s own warranty, not Buildmark.¹
Damage caused by drainage systems or sprinklers operating as designed is excluded.¹⁰
Anything altered after NHBC’s final inspection, and defects arising from that work, falls outside cover.³

Warranty or Buildings Insurance?

The warranty covers construction defects; buildings insurance covers events. If a pipe leaks because it was installed badly or the materials did not meet Building Regulations, that is a Buildmark matter during years one and two. If a pipe bursts because it froze, or someone drilled through it, the resulting water damage is a buildings insurance question. The NHBC policy specifically excludes accidental damage and anything covered by other insurance.¹

Sometimes the two overlap. A construction defect causes a pipe to fail, which then floods the kitchen. In that case, notify both your warranty provider and your buildings insurer and let them sort out the split.¹¹

Reporting a Plumbing Defect

Years One and Two

Report the defect to the builder in writing, by email or letter. Give the location, the date you noticed it, and a clear description. Keep every piece of correspondence.¹² Give the builder a reasonable period to respond and repair. If they don’t act, or their response is inadequate, run their internal complaints procedure.

Once you have a final written response, or 30 days have passed without one, you can ask NHBC to use its resolution service.¹³ NHBC assesses the problem and, where the builder has failed its requirements, issues a resolution report telling the builder what to do. If the builder still does not comply, NHBC steps in under its guarantee.

Years Three to Ten

Claims go straight to NHBC. Call the claims team on 0800 035 6422 or submit through the NHBC website.¹⁴ Internal plumbing won’t qualify, but an underground drainage defect may.

Evidence to Gather

Take photographs of the defect, log when you first noticed it and how it has changed, and keep every email and letter. For more serious Section 3 claims, NHBC may expect a report from a structural engineer or building surveyor rather than photographs alone.¹² Don’t repair the defect yourself before the claim is assessed; doing so can destroy the evidence the inspector needs.

If NHBC Turns the Claim Down

A rejection is not final. The Financial Ombudsman Service can review complaints about NHBC, but usually only once the matter touches regulated insurance activity, which in practice tends to mean after a resolution report has been issued and the builder has failed to carry out the required work.¹⁵ The FOS can order NHBC to pay for repairs or settle in cash at commercial rates rather than NHBC’s own contractor rates.⁹

The New Homes Ombudsman can look at complaints about breaches of the New Homes Quality Code, including failures to resolve defects within agreed timescales. Developers that don’t comply with its decisions can face fines, mandatory retraining, or removal from the Register of Developers.¹⁶

You also keep legal rights against the builder separately from the warranty. The Consumer Rights Act 2015 requires work to be carried out with reasonable care and skill. The Defective Premises Act 1972 requires a dwelling to be fit for habitation; following the Building Safety Act 2022, the limitation period for prospective claims under that Act is 15 years.¹⁷ Standard breach-of-contract claims carry a six-year limitation period from completion.¹⁸

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