Summary
New roofs can have defects. The quality of a roof installation depends on the skill and care of the installer, the quality of materials specified, and the specification of the works. An independent post-installation survey is the only way to verify that the work meets acceptable standards without relying on the contractor's own assessment. See also: Common Defects Found on Newly Installed Roofs.
Why New Roofs Are Not Always Defect-Free
The roofing industry, like all trades, contains a wide range of skill levels and standards. A newly installed roof may look attractive from street level whilst concealing a range of problems that will only become apparent during heavy rain, frost, or over time.
The absence of visible defects does not indicate the absence of actual defects. Many of the most significant roofing failures originate at details that are concealed within the construction — flashings tucked behind cladding, underlay laps hidden beneath tiles, fixings obscured by the covering material itself.
The Role of Workmanship
Roofing is a skilled trade. Correctly installing a pitched tile or slate roof requires knowledge of gauge, lap lengths, fixing patterns, valley details, verge treatment, ridge construction and flashing installation. Each element must be correct and compatible with the others.
An experienced roofer working carefully can produce an excellent result. A less experienced operative, a rushed crew, or a contractor cutting costs through substandard materials can produce a roof that appears complete but fails to perform.
Workmanship defects include:
- Tiles or slates laid to an incorrect gauge — affecting lap length and therefore weather resistance
- Insufficient nail fixings — allowing tiles to lift in wind
- Flashings dressed inadequately into masonry — creating a path for water ingress
- Ridge tiles bedded in mortar without mechanical fixings — a common failure under BS 5534
- Valleys formed incorrectly — directing water behind coverings rather than into the drainage channel
Material Quality and Specification
Not all roofing materials are equal. Substandard or inappropriate materials can perform acceptably in the short term but fail prematurely. Issues include:
- Underlay specified below the required standard for the pitch and exposure of the roof
- Low-quality mortar used for ridge bedding — prone to cracking in frost
- Substandard lead or alternative flashing materials at inadequate thickness
- Reclaimed or second-hand slates of unknown age and condition mixed into a new installation
- Concrete tiles used on a pitch below the manufacturer's minimum recommendation
Ventilation Deficiencies
Many new roof installations are deficient in ventilation. This is one of the most common findings on post-installation surveys. Inadequate ventilation causes condensation to accumulate in the loft space, which over time leads to:
- Mould growth on rafters and joists
- Wet rot in structural timbers
- Deterioration of insulation
- Damp and water staining visible on ceiling linings
For more on this topic, see: Do Roofs Always Need Ventilation?
Expert Commentary
"Post-installation surveys are among the most valuable work we undertake. In the majority of cases, we find at least one element that has not been installed correctly — often at a flashing or a ridge detail. Most issues are straightforward to rectify when identified early. Left unaddressed, the same defects can cause structural timber damage, ceiling collapse or extensive damp spread within a few years. The cost of remediation rises dramatically the longer a defect remains undetected."
Common Post-Installation Defects by Category
Flashings
Flashings seal the junction between the roof covering and adjacent structures — chimneys, dormer walls, parapet walls and roof penetrations. Poorly installed flashings are the single most common cause of water ingress in buildings with recently re-roofed properties.
Common flashing defects include insufficient step flashing at chimney sides, counter flashings not properly chased into masonry, and the use of oversized pieces of lead that are prone to fatigue cracking through thermal movement.
Ridge and Hip Tiles
Since the introduction of BS 5534:2014, mechanically fixed ridge tiles have been the standard requirement. Mortar-only bedding of ridge tiles is no longer acceptable practice. Many installations continue to use mortar bedding without mechanical fixings, creating a significant wind uplift risk and potential safety hazard.
Gutters and Rainwater Goods
Fascias, soffits and gutters are often replaced as part of a re-roofing contract. Common installation defects include incorrect fall on gutters (causing standing water and overflow), inadequate outlet sizing, and poorly sealed joints that allow persistent dripping onto exterior walls.
Underlay and Breathability
The underlay is a critical secondary weathering line beneath the tile or slate covering. Low permeability underlays on pitched roofs that rely on them for ventilation are a common specification error, leading to the condensation issues described above.
The Warranty Consideration
Many roofing contractors offer workmanship guarantees of varying terms. The value of any guarantee depends entirely on the continued trading of the contractor offering it — and many smaller roofing firms do not survive for the duration of their guarantee period.
An independent survey provides objective evidence of condition at a defined point in time. Where defects are identified during the contractor's defects liability period, the survey report provides the documentary evidence needed to require rectification.
See also: Can a Roofer Inspect Their Own Work?
What Does a Post-Installation Survey Cover?
An independent post-installation roof survey from UK Roof Surveys includes:
- Visual inspection of all accessible roof surfaces and elements
- Assessment of flashings, valleys and junctions
- Inspection of ridge and hip tile fixings
- Evaluation of gutters, fascias and soffits
- Loft space inspection for ventilation adequacy and moisture
- Drone photography where required for high or inaccessible areas
- Written report with photographs and condition ratings
- Remedial recommendations with estimated costs where applicable
Frequently Asked Questions
Should I get a survey before the contractor leaves?
It is preferable to arrange a post-installation survey within the defects liability period — typically 12 months — whilst the contractor still has an obligation to rectify defective work. However, a survey at any point provides useful evidence of current condition.
Can I commission a survey if the contractor disputes the defects?
Yes. An independent survey report from a qualified specialist provides objective evidence. Because UK Roof Surveys has no commercial interest in the outcome, our reports carry weight in disputes. We do not carry out repairs and have no incentive to exaggerate findings.
What if the survey finds the roof is fine?
A clean survey result is a valuable outcome. It provides documented evidence that the roof was inspected and found to be in acceptable condition at a defined date. This protects you in any future dispute about when a defect originated.
How much does a post-installation survey cost?
Costs vary by property size and complexity. See our guide: What Does a Roof Survey Cost?
Not sure whether you need a specialist roof survey? Our roof survey checker helps you assess whether further investigation may be worthwhile for your situation.