Structural Warranties for London Building Works: What They Cover and When You Need One

A structural warranty (more formally a 'latent defects insurance' policy) provides cover for physical damage to the load-bearing elements of a building caused by defects in design, workmanship, or materials. The warranty typically covers:

• •Foundations, substructure, and ground-bearing elements
• •Load-bearing walls, beams, and structural frame
• •Roof structure (rafters, purlins, ridge, hip members)
• •Floors and floor structures
• •External envelope integrity where structural in nature

• **What it does NOT cover:**
• •Normal wear and tear
• •Cosmetic defects (cracked plaster, paint, minor settlement cracks)
• •Non-structural elements (windows, doors, kitchen units, floor finishes)
• •Damage caused by the owner's misuse or lack of maintenance
• •Consequential losses beyond repair of the structural damage itself

**Cover period:** Most structural warranties run for 10 years from the date of practical completion. Some providers offer 12 or 15-year policies at higher cost. The first two years typically also include a 'developer's defects' period in which the builder is responsible for making good broader defects — but this period is between the client and the builder, not the insurer.

**Who benefits:** The warranty is primarily valuable in two scenarios: 1. The original client — protection against the contractor becoming insolvent or unavailable to resolve a structural defect after completion 2. Future buyers — mortgage lenders often require a structural warranty (or satisfactory equivalent) on properties less than 10 years old before they will lend against them

**New-build dwellings:** For a newly constructed dwelling (including a new house or flat built by a developer or self-builder), most mortgage lenders require evidence of structural warranty cover before they will lend. The most commonly accepted warranties are NHBC Buildmark and Premier Guarantee, among others. Without a warranty, the property may be difficult to mortgage and therefore difficult to sell.

**Conversions creating new dwellings:** Where a building (a commercial property, a large house) is converted into multiple new flats or dwellings, the same mortgage lender requirements typically apply. A structural warranty or professional consultant's certificate (PCC — a surveyor's report confirming the building was properly constructed) is commonly required.

**Extensions and loft conversions:** Here the picture is different and frequently misunderstood. Extensions and loft conversions to an existing dwelling generally do NOT require a structural warranty as a legal or mortgage condition. The building already exists; the extension is an addition to it. Building Regulations approval and a Completion Certificate from the local authority (or a private approved inspector) satisfy the legal compliance requirement.

• However, a warranty may still be advisable where:
• •The extension is large and structural in nature (basement, major rear extension over two storeys)
• •The client intends to sell the property within 10 years and wants to be able to provide documentary assurance to a future buyer's surveyor
• •The project involves a self-builder or less-established contractor where the risk of insolvency is higher

**Refurbishments:** For refurbishments (even comprehensive strip-back refurbishments), structural warranties are not generally applicable unless the work involves significant structural intervention creating what is in effect a new structural frame.

**The practical rule:** If the work creates a new dwelling that will be sold or mortgaged, a structural warranty is almost certainly required. If the work extends or improves an existing owner-occupied dwelling, a structural warranty is optional and is most valuable as protection against contractor insolvency or for reassurance to a future buyer.

**NHBC Buildmark:** The market-leading structural warranty for new-build residential in the UK. Available to NHBC-registered developers and builders. Not available to individual clients commissioning a contractor who is not NHBC-registered. 10-year cover. Required by most mortgage lenders as an acceptable warranty.

**Premier Guarantee:** A privately underwritten structural warranty accepted by most mortgage lenders as equivalent to NHBC Buildmark. Available to self-builders and developer projects through registered builders or professional oversight routes.

**LABC Warranty:** Offered in association with Local Authority Building Control. Available to self-builders and developer schemes.

**NHBC Self-Build:** NHBC offers a separate product for self-builders (Solo policy) allowing individual self-builders to obtain NHBC cover even if their contractor is not NHBC-registered, subject to NHBC inspection during construction.

**Professional Consultant's Certificate (PCC):** An alternative to a structural warranty accepted by many (but not all) mortgage lenders. A qualified professional (typically an architect, structural engineer, or building surveyor) provides a signed certificate confirming they inspected the works at appropriate stages and that the building was properly constructed. PCCs do not provide the same insurance coverage as a warranty but they may satisfy a lender's requirement and are often significantly cheaper.

• **Typical costs:**
• •NHBC or Premier Guarantee on a new dwelling: typically £1,200–£4,000 depending on size (structured as a percentage of build cost, often 0.3–0.8%)
• •Professional Consultant's Certificate: £800–£2,500 depending on size and inspection frequency
• •Extension or loft conversion warranty (where one is sought): £400–£1,500

**Timing:** A structural warranty must be arranged before construction starts — the inspections that support the warranty cover must take place at key stages during the build. Attempting to obtain a warranty after practical completion is not possible with most providers.