Building Warranties and Structural Warranties: What They Are and Do You Need One?

**What a building warranty is**:

A building warranty (the generic term) is a form of latent defects insurance. It provides the owner and future owners of the property with protection against structural defects that were present at the time of construction but were not discovered immediately — 'latent' meaning hidden. The policy typically runs for 10 years from the date the building is certified as complete.

*What a building warranty typically covers*:

• •Major structural defects in foundations, load-bearing elements, roof structure, and external envelope
• •Defects that arise from inadequate design, workmanship, or materials in the structural elements
• •Consequential damage arising from a warranted structural defect (e.g., internal damage caused by a structural failure)

*What a building warranty does NOT typically cover*:

• •General wear and tear and deterioration
• •Condensation or dampness not resulting from a structural defect
• •Routine maintenance items (gutters, sealants, decoration)
• •Defects caused by the owner's negligence or alterations after completion
• •Non-structural items (kitchen appliances, internal finishes, M&E equipment)
• •Consequential losses (cost of alternative accommodation, relocation)

*How the coverage period is structured*:

• Most warranties have a two-period structure:
• •Years 1–2 (Builder's Period): The contractor who built the property is primarily responsible for defects. The warranty insurer backs this responsibility.
• •Years 3–10 (Structural Insurance Period): The contractor's primary responsibility for defects diminishes; the insurer provides structural coverage directly.

This means that in the first 2 years, the homeowner should be pursuing the contractor for defects (backed by the retention mechanism in the contract); from year 3, the insurer provides the primary remedy.

**The major building warranty providers in the UK**:

*NHBC (National House Building Council)*:

The most widely recognised warranty provider for new build residential properties. NHBC's 'Buildmark' warranty is standard for new homes from volume housebuilders. NHBC inspectors visit the site at key stages and must certify completion before the Buildmark policy is issued.

*LABC Warranty*:

The Local Authority Building Control (LABC) structural warranty product. Combines Building Control inspection with warranty provision — available to projects using Local Authority Building Control rather than an Approved Inspector. Available for extensions over a threshold value.

*Premier Guarantee / LABC New Homes*:

An insurance-backed structural warranty provider used by self-builders, custom-builders, and major extensions/conversions.

*CABE / Checkmate / ABC+ Warranty*:

Specialist warranty providers for conversions, barn conversions, HMO conversions, and non-standard construction. Used where NHBC and LABC warranties are not available or appropriate.

*Build Assure / ProBuild Warranty*:

Used for major extensions and conversion projects, particularly where the contractor is not registered with NHBC.

**The difference between a building warranty and Building Control certification**:

• Building Control (Part B through Part L compliance) and a building warranty are separate:
• •A Building Control completion certificate confirms the building meets the Building Regulations at the point of completion — it is not a warranty against future defects
• •A building warranty is an insurance policy providing 10-year cover — it is not a regulatory compliance certificate

Some mortgage lenders accept a Professional Consultant's Certificate (PCC) from a qualified professional (architect or engineer) as an alternative to a structural warranty for conversions and major extensions — see below.

**The mortgage lender's perspective**:

Mortgage lenders typically require evidence that a newly built or significantly converted property has been built to an acceptable standard and is protected against major structural defects. Their primary concern is the security of the property (the collateral for the loan) — if the building has significant structural defects, the lender's security is impaired.

**When mortgage lenders require a warranty**:

*New build properties*:

• For a newly built house or flat (including self-build), most mortgage lenders require either:
• •An NHBC Buildmark warranty, or
• •An equivalent warranty from an NHBC-approved provider, or
• •A Professional Consultant's Certificate (PCC) signed by a qualified architect, engineer, or surveyor who inspected the build at key stages

*Conversions (loft to dwelling, barn, commercial to residential)*:

For a property that has been converted from one use to residential, many mortgage lenders require a warranty or PCC if the conversion was completed within the last 10 years.

*Major extensions*:

For domestic extensions, most mortgage lenders do not require a structural warranty for the extension itself — particularly if the works have Building Control approval and a completion certificate. However, if the extension significantly changes the character of the property (e.g., the extension roughly doubles the floor area), or if a mortgage is being applied for on the extended property shortly after completion, the lender may ask for additional evidence of quality.

**The Professional Consultant's Certificate (PCC)**:

A PCC is a Certificate of Supervision issued by a qualified professional (architect, building surveyor, or civil/structural engineer) who has inspected the building at key stages of construction and is prepared to certify that the works were carried out to an acceptable standard.

• *When a PCC is appropriate*:
• •Conversions where a warranty provider is unwilling to accept the project
• •Self-build or custom-build projects where the volume/specification does not fit the standard warranty products
• •Major extensions where a mortgage lender requests evidence but a full structural warranty would be disproportionate

• *What a PCC is not*:
• •It is not a warranty — it does not provide insurance cover if defects arise
• •It places professional liability on the signatory — the professional's PI insurance covers claims arising from their certification
• •Lenders vary in whether they accept a PCC — confirm with the specific lender before relying on one

**The Council of Mortgage Lenders (UK Finance) Handbook**:

The UK Finance Mortgage Lenders' Handbook (the standard reference for UK residential conveyancing) specifies what evidence of construction quality is acceptable for mortgage purposes. Part 1 (general requirements) and Part 2 (specific lender requirements) must both be checked. The standard UK Finance position for properties under 10 years old is that either a recognised structural warranty or a PCC from a qualified professional is required.

**When you need a building warranty**:

*You should strongly consider a building warranty if*:

• •You are building a new dwelling (self-build, barn conversion, HMO conversion to a separate self-contained flat)
• •The conversion or extension significantly increases the floor area (more than 30–40% addition to the existing house)
• •You intend to sell the property within 10 years of completion (buyers' mortgage lenders may require one)
• •Your mortgage lender requires one for the re-mortgage of the extended property
• •You are a developer converting a commercial or industrial building to residential use

*You probably do not need a building warranty for*:

• •A domestic extension to an existing owner-occupied house where you will continue to occupy the house
• •A loft conversion that does not create a separate dwelling
• •An internal renovation (no structural changes)
• •Any project where you are confident you will not sell or re-mortgage within 10 years

**How to get a building warranty — the process**:

1. *Apply to a warranty provider before construction starts*: Most warranty providers require that they are appointed before any groundworks commence — they need to inspect the foundations and key structural stages during construction, not just at completion. Retrospective warranty applications (applied for after completion) are usually possible but more expensive and may require intrusive surveys.

2. *Warrant provider registers the project and appoints an inspector*: The warranty provider registers the project and appoints a technical inspector to carry out stage inspections during construction (similar to Building Control inspections but focused on the warranted structural elements).

3. *Stage inspections*: The inspector visits at key stages — foundations, structural frame/walls to DPC, floor structure, roof structure, and completion.

4. *Certificate issuance at completion*: If the inspector is satisfied that the project has been built to an acceptable standard, the warranty policy is issued at practical completion. The policy document is issued to the developer/self-builder and can be assigned to subsequent owners.

*Cost of a building warranty*:

| Project type | Typical warranty cost | |---|---| | Domestic extension (over £100,000) | £1,500–£3,000 | | Loft conversion to a separate flat | £2,000–£4,000 | | HMO conversion (3–6 beds) | £2,500–£5,000 | | Self-build new house | £1,500–£4,000 (depends on value) | | Commercial to residential conversion | £3,000–£8,000 |

*When to involve the contractor*: The contractor does not typically organise the building warranty — the client/developer does. The contractor needs to be aware that stage inspections will occur so they can notify the warranty inspector at the required stages (similar to Building Control notification). Some experienced principal contractors (like RCB) routinely advise clients on warranty requirements as part of the pre-construction process.