New build properties in Kent — including the significant volume of housing development in the Tonbridge, Paddock Wood and Maidstone corridors over the last 15 years — are covered by the NHBC Buildmark warranty for 10 years. But NHBC cover is more limited than many homeowners realise, and many roofing defects that manifest in years 3-10 go unclaimed because the owner doesn't know their rights or leaves it too late. This guide explains what to look for and what to do.
What NHBC Buildmark Covers for Roofing
| Period | Coverage | Notes |
|---|---|---|
| Years 1-2 | Builder's obligation to fix defects | Report to builder directly |
| Years 3-10 | Major structural defects via NHBC | NHBC handles claims direct |
| Years 1-10 | Contaminated land and certain water ingress | See policy schedule |
| Any time | Roof defects causing major structural damage | Requires NHBC assessment |
What NHBC does not cover: cosmetic defects after year 2, normal wear and tear, damage from external events, maintenance-related deterioration, or defects that don't meet the 'major damage' threshold.
The critical window: most roofing defects on new build Kent properties manifest between years 2 and 8 as mortar dries and settles, tile fixings bed in, and flat roof membranes experience their first thermal cycling. An inspection in year 3-4 and again in year 7-8 catches most of these while NHBC cover still applies.
NHBC warranty periods: The NHBC Buildmark warranty (10th edition, 2023) divides cover into: years 1–2 (builder's obligation to fix defects), years 3–10 (NHBC insurance against major structural damage). Roofing defects that cause water ingress and damage to the building structure may be claimable in years 3–10 subject to NHBC assessment. Source: NHBC Buildmark Warranty 10th Edition, 2023
Common Roofing Defects on New Build Kent Properties
1. Ridge and Verge Mortar Failure
The most common roofing defect reported on new build Kent properties. OPC cement ridge bedding laid in cold or wet conditions during construction dries improperly, develops surface cracks within 2-5 years, and allows water entry. By year 6-8 the affected tiles may be loose. This is a builder's defect in years 1-2 and potentially a structural defect claim under NHBC in years 3-10.
2. Flat Roof Membrane Defects on Extensions
New build Kent properties with flat-roofed garages and kitchen extensions increasingly use GRP or EPDM. Installation defects — inadequate deck preparation, voids in the laminate, poorly bonded upstands — are not immediately visible but create failures within 5-10 years. A GRP flat roof that fails at year 4 on a new build is almost certainly an installation defect.
3. Incorrect Tile Fixing
Tile fixing on new builds is frequently carried out under time pressure. Nails missed, wrong length nail for tile thickness, tiles not fully engaged on the batten — all create movement that becomes visible by year 3-5. Any tile displacement on a property under 10 years old should be treated as a potential defect claim.
4. Lead Flashing Specification
Code 3 lead on new build chimney flashings is a recurring defect. It meets a minimal specification threshold but fails within 10-15 years on exposed Kent positions. A chimney flashing failure on a property under 10 years old is a potential defect — inspect and document before the warranty expires.
5. Inadequate Ventilation
Cold roof construction without adequate ventilation causes interstitial condensation — moisture accumulating in the batten space, wetting the underside of tiles and eventually the timber. This is an invisible defect that manifests as damp in the loft space 3-8 years after construction. New Building Regulations require ventilation at eaves and ridge — if your new build Kent roof lacks this, it is a building regulation defect.
Inspection and NHBC evidence report for new build defects — call 0173 224 1138
📞 0173 224 1138What to Do If You Find a Defect
- Photograph immediately — document the defect before any weather changes the visible condition.
- Year 1-2: contact the builder — they are obliged to remedy defects under the Buildmark warranty.
- Year 3-10: contact NHBC directly — if the builder disputes or is unresponsive, NHBC handles the claim.
- Get an independent inspection report — NHBC requires evidence. A written report from an NFRC-registered contractor carries weight.
- Don't delay — the 10-year warranty is a hard cutoff. A defect reported at year 11 receives no NHBC cover.
The Pre-Expiry Inspection
An inspection in year 7-9 — before the NHBC warranty expires — is the most cost-effective action a new build Kent homeowner can take. We carry out pre-expiry NHBC inspections in Tonbridge and across Kent: on-roof survey, written report with photographs, and advice on which findings warrant a formal NHBC claim before the warranty closes.