Roof Defect Claims Against Contractors: Expert Witness Evidence

A roofing expert witness is an independent chartered building surveyor who inspects a defective roof and gives the court an opinion on three things: whether the contractor's work fell below a reasonable standard, whether that failure caused the leak or damage, and what it will cost to put right. In roof defect claims against contractors that evidence usually decides the outcome, because the roofer will say the work was sound and the owner cannot prove otherwise from photographs alone. This guide explains when expert evidence is needed, what the expert examines, the time limits and what the report costs.

When does a roof defect claim need expert evidence?

Most disputes start the same way: a new or re-covered roof leaks, tiles slip, a flat roof ponds or the ceiling below stains within months of the work. The contractor blames the weather, the old structure or another trade. Under section 49 of the Consumer Rights Act 2015 a trader must carry out a service with reasonable care and skill, and a homeowner can require the work to be done again or claim a price reduction; business customers have a similar term implied by the Supply of Goods and Services Act 1982. Whether the roofer met that standard is a technical question, which is why claims for poor workmanship turn on independent evidence rather than the owner's own view.

Expert evidence is normally needed where:

• the contractor denies the work is defective or says the leak has another cause;
• the remedy is disputed, typically a patch repair against stripping and re-covering the roof;
• a guarantee provider or insurer has rejected a claim on the ground of workmanship or maintenance;
• water has damaged ceilings, timbers, insulation or contents and the sums need to be justified.

The roof should be inspected before another contractor strips it. Once the covering is removed the evidence of how it was fixed is gone, so only emergency weatherproofing should be done first, as explained in when to hire an expert witness for construction defects.

What does a roofing expert witness examine?

The expert's starting point is the contract: the quotation, specification, drawings and any manufacturer's system the contractor agreed to install. The roof is then measured against that and against recognised standards. Those most often cited are:

• BS 5534, the code of practice for slating and tiling, covering battens, underlay, headlap and gauge, and the mechanical fixing of tiles, ridges and hips;
• BS 6229 for flat roofs, including the falls needed to shed water and avoid ponding;
• BS 5250 on moisture and condensation, relevant where a "leak" turns out to be condensation in a poorly ventilated or insulated roof;
• the Building Regulations, since substantial re-roofing is generally notifiable work and a missing completion or competent person scheme certificate is evidence in itself;
• manufacturers' fixing instructions and the terms of any product or insurance-backed guarantee.

On site the expert records the pitch, covering, laps, fixings, flashings, abutments, valleys, gutters and penetrations, opens up selected areas where the owner agrees, and checks the roof void for staining, daylight, wet insulation and decay. High or fragile roofs are often surveyed first by drone or pole camera, and moisture mapping or a leak detection test may be recommended for flat roofs. What happens on the day is covered in the guide to the expert witness site inspection.

Proving breach, causation and the cost of repair

A court needs more than a list of faults. The report has to answer three linked questions:

• Breach. Which items fall below the contract, the standards or reasonable practice, and which are merely untidy or within tolerance.
• Causation. Whether those defects caused the water ingress, or whether the real cause is condensation, storm damage, a blocked gutter, lack of maintenance or an existing fault in the structure that the roofer was not engaged to fix.
• Quantum. The reasonable remedial scheme and its cost, with reasons for preferring local repair or full replacement, plus scaffolding, internal making good and any allowance for betterment where the replacement roof would be better than the one contracted for.

Where several items are in dispute the expert usually sets them out in a Scott schedule so the judge can decide each in turn. The wider framework is explained in expert witness evidence in building defects claims. The expert's overriding duty under CPR 35.3 is to the court, so a credible report also records what the contractor did properly.

Time limits and the route to court

In England and Wales a claim for breach of contract must generally be issued within six years of the breach, or twelve years if the contract was signed as a deed. A claim in negligence, where one is available, can run for three years from the date a hidden defect could reasonably have been discovered if that is later, subject to a fifteen-year long stop under the Limitation Act 1980. Where defective work has left a dwelling unfit for habitation, the Defective Premises Act 1972 may give a further route. A solicitor should confirm the dates in each case; the practical point is that evidence deteriorates far faster than the limitation period runs.

Before proceedings the parties are expected to exchange a letter of claim, a response and the key documents, under the Practice Direction on Pre-Action Conduct or, for claims heading to the Technology and Construction Court, the Pre-Action Protocol for Construction and Engineering Disputes. Many roofing disputes settle at this stage once a reasoned report is disclosed. If not, the value sets the track: up to £10,000 on the small claims track, where expert evidence needs the court's permission and only £750 of each expert's fee is recoverable; up to £25,000 on the fast track; and up to £100,000 on the intermediate track. On the lower tracks the court often directs a single joint expert and written evidence only. The economics are set out in expert report costs in small claims builder disputes.

How much does a roofing expert witness report cost?

RICS chartered surveyors acting as expert witnesses generally charge £150 to £300 an hour. A CPR Part 35 report in a straightforward matter typically costs £5,000 to £15,000, complex or multi-property cases £20,000 to £50,000 or more, and court attendance £1,000 to £2,000 a day. Access equipment, opening up and laboratory testing are charged separately. For a lower-value dispute a proportionate first step is an advisory specific defect report or roof survey, which is often enough to support a letter of claim; the same surveyor can usually be instructed to prepare a Part 35 report if the dispute goes further. The guide to expert witness costs in the UK gives a fuller breakdown.

Instruct a roofing expert witness through Survey Merchant

Survey Merchant provides RICS chartered building surveyors as expert witnesses for roof defect claims across England and Wales, drawn from a national panel of more than 2,400 surveyors. The panel's experts inspect pitched and flat roofs, including by drone survey where access is difficult, prepare CPR Part 35-compliant reports in line with the RICS practice statement for surveyors acting as expert witnesses, accept single joint expert and party appointments and attend court when required. Homeowners, landlords, contractors and solicitors can all instruct, and fixed fees are quoted wherever the scope allows. Visit the construction expert witness page, see all expert witness services, call 0204 579 8270 or use the contact form to discuss the claim with the panel.