Why Warranties and Guarantees Matter
A building warranty is a commitment — from the contractor, manufacturer, or an insurance company — that a specific element of the work will perform as intended for a stated period. If it does not, the warranty provides a mechanism for remedy.
For buyers and lenders, warranties on significant works provide confidence in the quality and longevity of the construction.
Types of Warranty and Guarantee
Contractor Workmanship Guarantee
Most reputable contractors offer a workmanship guarantee — typically 1–2 years on labour. This means that if defects arise from poor workmanship within that period, the contractor will return and repair at no extra cost.
However, this guarantee is only as reliable as the contractor's continued existence. If the contractor has ceased trading, the guarantee is worthless.
Insurance-Backed Guarantees (IBGs)
An IBG is a workmanship warranty underwritten by an insurance company. If the contractor who carried out the work ceases to trade, the insurance company steps in to honour the guarantee.
IBGs are available from several providers in the UK market (typically for 10 years) and are offered by schemes such as the Federation of Master Builders (FMB), TrustMark, and various specialist warranty providers.
When IBGs are particularly important:
- When selling a property — buyers' solicitors increasingly ask for IBGs on significant works
- When remortgaging — some lenders require an IBG on major structural works
- When the contractor is a small business without a long trading history
Specialist System Warranties
Many building product manufacturers offer warranties on their specific systems:
- Flat roof membrane warranties: Single-ply membrane systems (EPDM, TPO, PVC) typically carry 20–25 year manufacturer warranties when installed by an approved installer
- Render system warranties: Leading render manufacturers (Weber, Parex, K Rend) offer warranties of 10–25 years on their products when installed by approved applicators
- Cavity wall insulation warranties: CIGA (Cavity Insulation Guarantee Agency) offers 25-year guarantees on cavity wall insulation
- Window warranties: Most window manufacturers offer 10-year guarantees on frames and sealed units
Structural Warranties (New Homes)
For new homes and major conversions (e.g., barn conversions), a structural warranty from a provider such as NHBC Buildmark, Premier Guarantee, or similar is standard. These provide 10-year cover for structural defects, with the first 2 years typically covered directly by the developer and years 3–10 by the insurance element.
For extensions and refurbishments, structural warranties of this type are less common — typically a combination of Building Control sign-off and an IBG is used instead.
Building Control Completion Certificates
A Building Control Completion Certificate is not a warranty — it confirms that the work was completed in compliance with the Building Regulations as they applied at the time of inspection. It is, however, a crucial document:
- It confirms that Building Control inspected and accepted the work
- Without it, subsequent buyers, solicitors, and lenders may be concerned about the legality of the work
- It may be difficult to obtain retroactively if lost
Keep all completion certificates in a secure place, and consider registering them on the local authority portal where available.
What Buyers' Solicitors Look For
When selling a property where significant works have been carried out, buyers' solicitors will typically ask for:
- Planning permission (if required) for the works
- Building Regulations completion certificate
- Party wall award (if applicable)
- Electrical installation condition report (EICR) for rewiring
- Gas safety certificates for gas works
- IBG or specialist system warranty where available
Missing documents can delay or complicate a sale. Some solicitors will advise their client to seek an indemnity insurance policy to cover the absence of documentation — but this is a workaround, not a solution.
RCB Design & Build
RCB issues workmanship guarantees on projects and supports clients in obtaining insurance-backed guarantees through accreditation schemes including TrustMark. We retain all Building Control documentation and compliance certificates and provide a comprehensive handover pack at project completion.