Building Warranty and Latent Defects Insurance — A Homeowner's Guide

A structural warranty is an insurance policy — purchased by the developer or contractor at the time of build — that provides a transferable guarantee to successive owners of the property against structural defects discovered within the policy period (typically 10 years).

**The key distinction**: a structural warranty is not a contractor's guarantee. A contractor's guarantee is a contractual promise from a specific business that if something goes wrong, they will fix it. A structural warranty is an insurance policy issued by a regulated insurer — it remains valid even if the contractor goes out of business.

• **What is covered?**
• Structural warranties typically cover:
• •Defects in the structural elements of the building (foundations, structural walls, floor structure, roof structure)
• •Damage resulting from such defects (e.g., water ingress through a defective roof structure)
• •The cost of remediation

• **What is not covered?**
• •Cosmetic defects (cracks in plaster, paint finish)
• •Damage caused by normal wear and tear or lack of maintenance
• •Defects in systems the homeowner is responsible for maintaining (boilers, appliances)
• •Works carried out after handover without the insurer's approval

**The two phases**: Most structural warranty policies operate in two phases: 1. **Developer's period** (years 1–2): defects of any kind that are the contractor's responsibility 2. **Insurance period** (years 3–10): structural defects covered by the insurer directly

• **Who issues structural warranties in the UK?**
• The best-known provider is NHBC (National House Building Council) — their Buildmark warranty is the most widely recognised in the UK and is accepted by virtually all mortgage lenders. Other providers include:
• •Premier Guarantee
• •LABC Warranty
• •Build-Zone
• •Protek
• •Global Home Warranties

Each provider has its own product, coverage terms, and acceptance by lenders — check lender acceptance before committing to a provider.

**New-build properties**: a structural warranty is required by virtually all UK mortgage lenders for new-build properties. Without one, the property is unmortgageable for most lenders.

**Loft conversions**: most residential loft conversions do not require a structural warranty — they are a conversion within an existing structure, not a new build. However, if the loft conversion is part of a property being sold shortly after completion, some buyers' solicitors will request evidence of structural warranty or professional indemnity insurance from the contractor.

**Extensions**: similarly, residential extensions typically do not require a structural warranty. Building Regulations compliance (confirmed by a completion certificate) is the standard evidence of construction quality for extensions.

**New dwellings / conversions to create a new dwelling**: when an existing building (such as a barn, commercial building, or garage) is converted into a dwelling, or when a new house is built, a structural warranty is typically required by mortgage lenders.

**HMO or flat conversions**: where a house is converted to create new separate dwelling units (flats or HMO rooms), lenders funding buyers of those units will typically expect a structural warranty.

**Self-build**: a structural warranty is strongly recommended for self-build projects — most lenders require one to release funds at practical completion.

**The professional consultant's certificate (PCC) alternative**: where a structural warranty is not available, some lenders accept a Professional Consultant's Certificate — a certificate issued by an architect, structural engineer, or other professional confirming that they have inspected the works at key stages and that the building has been built to an acceptable standard. PCCs have limitations and are not accepted by all lenders — check lender requirements before relying on a PCC.

• Structural warranty costs vary by provider and depend on:
• •The type of project (new build, conversion, loft conversion)
• •The floor area of the dwelling
• •The number of dwellings (development of several units)
• •The building method (standard masonry, timber frame, SIPs)

**Approximate costs (2025)**:

**New-build house (3-bed, standard construction)**: £1,500–£4,000 for a 10-year structural warranty

**Single new-build flat**: £800–£2,500

**HMO conversion (5-bedroom house to 5 individual units)**: £2,500–£6,000

**Development of 5 new houses**: £5,000–£15,000 (premium per unit decreases at scale)

**Self-build (4-bedroom house)**: £2,000–£5,000

**Key point**: the warranty cost is typically 0.3–0.8% of the construction cost. For a £500,000 build, this represents £1,500–£4,000 — modest in the context of the overall investment.

**Timing**: the warranty application should be submitted before works start (or as early in the programme as possible). Providers carry out site inspections at key stages — foundations, structural frame, weathertight shell, and practical completion — and will not issue the certificate until all stage inspections are complete.