New Build Defects Claims: Expert Witness Evidence Against Developers

A new build defects expert witness is a chartered building surveyor or structural engineer who gives independent opinion evidence on whether a new home was built to the required standard, what caused the defects, who is responsible and what it will reasonably cost to put right. When a developer disputes liability, a warranty provider rejects a claim or the defects are serious enough for court, the outcome turns on that evidence. This guide explains the claim routes against developers and warranty providers in England and Wales, what the expert must establish on each, and what the evidence costs.

Snag or defect: why the distinction decides the claim

Every new home has snags: paint runs, sticking doors and grout gaps that the developer is expected to correct in the first weeks and that are judged against published tolerances for finishes. A defect is work that fails a technical standard that applied when the home was built: missing cavity barriers, inadequate roof ventilation, undersized lintels, poor drainage falls or a damp-proof course bridged by external ground levels. Developers often describe a genuine defect as a snag or "normal shrinkage", because that limits their obligation.

The first job of the panel's experts is therefore classification. Each item is tested against the Building Regulations in force at the time, the NHBC Standards or the warranty provider's equivalent technical manual, British Standards for workmanship, the manufacturer's instructions and the specification the home was sold against. The new-build defects statistics guide sets out how common serious items are and how often complaints succeed.

Claims against the developer: contract, the codes and the Defective Premises Act

• Contract. The sale contract and building agreement will usually require the home to be built in a good and workmanlike manner, to the specification and in compliance with the Building Regulations, and the warranty obliges the developer to repair defects reported in the first two years. Where the developer refuses, or a repair fails, the expert's report identifies the breach, the remedial scope and the cost.
• The consumer codes. Developers registered with the New Homes Quality Code answer to the New Homes Ombudsman Service; those still under the Consumer Code for Home Builders use its adjudication scheme. These routes are cheaper and faster than court, but the usual remedy is a direction to repair and compensation limits are modest, so they suit outstanding snag lists rather than structural failures.
• The Defective Premises Act 1972. Section 1 requires anyone taking on work in connection with the provision of a dwelling to do it in a workmanlike or professional manner, with proper materials, so that the dwelling is fit for habitation when completed. The duty is owed to the first buyer and every later owner. The Building Safety Act 2022 extended the limitation period to 15 years for homes completed after June 2022 and 30 years for homes completed before it, reviving claims that were previously time-barred; the Building Safety Act claims guide covers this in more detail.

The Defective Premises Act route has a higher threshold than a contractual claim. The expert must show not just that the work was defective but that the defects, taken together, made the dwelling unfit for habitation when completed: structural instability, serious damp, dangerous electrics, a fire-safety failure or similar. A long list of cosmetic snags will not meet it.

Claims against the warranty provider in years three to ten

After the two-year defects period, the structural section of a ten-year warranty responds only to physical damage caused by a defect in specified elements, usually foundations, load-bearing walls, roof structure, chimneys and some cladding and retaining elements. Minimum claim values apply, and exclusions for condensation, wear and tear and anything that should have been reported in the first two years are routinely cited when a claim is rejected. The NHBC warranty guide explains the three stages of cover and the claims process.

In a disputed warranty claim the expert's evidence addresses the four questions the policy wording turns on: whether the element is one the policy covers, whether the damage results from a defect rather than wear, neglect or alteration, whether it is physical damage of the kind the policy responds to, and whether the provider's proposed repair is a proper and permanent remedy. The last point matters where a localised repair is offered for a systemic defect, such as missing wall ties across a whole elevation. Because the insured years are an insurance policy, an unresolved complaint can usually go to the Financial Ombudsman Service, and the same report serves that process.

What must a new build defects expert witness establish?

Whatever the route, the report follows the structure expected from a building defects expert witness.

• Condition. A photographed record of each item, with opening up, a drainage CCTV survey or thermal imaging where the cause is hidden. A snagging report from completion is valuable as a contemporaneous record of what was reported and when.
• Standard and breach. The requirement each item had to meet, cited by document and clause as it stood at the date of construction, and the respect in which the work fails it.
• Cause. Whether the failure is one of design, workmanship or materials, and whether it was present at completion or arose from later use or alteration.
• Consequence. Unfitness for habitation for a Defective Premises Act claim, physical damage for a warranty claim, or the loss flowing from the breach for a contract claim.
• Remedy and cost. A remedial specification, priced by a quantity surveyor where the sums justify it, with any betterment identified so the figure survives cross-examination.

Reports for litigation comply with CPR Part 35 and Practice Direction 35, and the expert's duty is to the court rather than to the paying party, which is why a developer or insurer finds a compliant report difficult to dismiss.

Court tracks, limitation and the pre-action stage

Claims of up to £10,000 go on the small claims track, where expert fees are capped at £750 and a single joint expert is the usual route. Claims up to £25,000 go on the fast track, up to £100,000 on the intermediate track, and larger or more complex claims on the multi-track, often in the Technology and Construction Court. The Pre-Action Protocol for Construction and Engineering Disputes requires a letter of claim and a meeting first, and most new-build disputes settle at that stage once the developer's adviser has read a properly referenced report. Contract claims carry six years from completion, or twelve under a deed, separate from the extended Defective Premises Act period; a solicitor should confirm the dates.

How much does new build defects expert evidence cost?

Expert witness surveyors on the panel charge £150 to £300 an hour. A CPR Part 35 report on a straightforward matter, such as a single dwelling with a defined list of defects and no intrusive investigation, generally falls within £5,000 to £15,000 and takes four to eight weeks from instruction where access is available. Complex matters, including estate-wide defects, multi-party claims or extensive opening up, run to £20,000 to £50,000 or more, and attendance at a hearing is charged at £1,000 to £2,000 a day. Investigation costs are additional. By contrast, a professional snagging inspection within the defects period costs a few hundred pounds and often avoids litigation altogether, because the developer remains obliged to fix what it records.

Instruct a new build defects expert witness through Survey Merchant

Survey Merchant provides RICS chartered building surveyors and structural engineers as expert witnesses in new-build defect claims against developers, contractors and warranty providers across England and Wales. The panel's experts prepare CPR Part 35 compliant reports, support New Homes Ombudsman, consumer code and Financial Ombudsman processes, take part in experts' meetings and attend court where required. Single joint expert and party appointments are accepted, and fixed fees are quoted wherever the scope is clear. To discuss a claim, see the construction expert witness service, the wider expert witness services, or contact Survey Merchant on 0204 579 8270.