Paperwork After the Bricks: Buying a Home With Unapproved Alterations in 2026

The Difference Between a Good Extension and a Documented One

A well-built rear extension can be the reason a buyer first notices a house. The same extension, if it lacks the right paperwork, can become the reason a lender hesitates, an insurer adds an exclusion, or a solicitor advises a retention. In 2026, with local authority resources stretched and buyers more aware of due diligence, unapproved alterations deserve a structured review rather than a hopeful assumption that time has resolved the issue.

The first step is to separate planning from building regulations. Planning permission controls whether the works are acceptable in principle, including their size, siting and effect on neighbours. Building regulations control how the works are constructed, including structural stability, fire safety, drainage, energy performance and ventilation. A house can have planning permission and still fail building regulations, or comply with building regulations while never having received planning consent. Buyers should not treat one document as proof of the other.

What Evidence to Request

For any alteration that appears to post-date the original house, ask the seller to provide a coherent evidence pack. Useful items include planning decision notices, building control completion certificates, structural calculations, architects' or engineers' drawings, warranty documents, party wall awards where relevant, and photographs taken during construction. Invoices and correspondence can help establish dates and the identity of the builder or inspector, but they are supporting evidence rather than proof of compliance.

Where the seller cannot produce these documents, the buyer's solicitor should consider local authority searches and targeted enquiries. In England and Wales, a local land charges search may reveal enforcement notices or planning histories, while additional enquiries can ask the local authority whether it holds records of building control approvals or completion certificates. Scotland and Northern Ireland have separate regimes, so the wording of enquiries should match the jurisdiction. A lawful development certificate can be relevant for planning status, but it does not cure a building regulations defect.

Why an Indemnity Policy Is Not Always the Easy Answer

Indemnity policies are often offered where works lack consent or certificates. They can be useful in limited circumstances, particularly where the risk is historic, the local authority is unlikely to take enforcement action, and the policy is accepted by the lender. They are not a substitute for technical evidence, and they do not make unsafe or non-compliant building work safe.

Insurers typically price and underwrite on the basis of known facts. If the buyer or their solicitor knows that a structural alteration was carried out without building regulations approval, the policy may be excluded, restricted or unavailable. A policy may also require the buyer to avoid contact with the local authority before inception, which can conflict with the need to make proper enquiries. More importantly, an indemnity policy usually protects against financial loss from enforcement; it does not fund remedial works if the extension is found to be structurally deficient. Buyers should read the scope, exclusions, excess and conditions carefully, and should not assume that a cheap policy resolves a material defect.

How Lenders and Insurers May React

Lenders focus on whether the property is suitable security. A minor conservatory or internal alteration may attract little comment. A substantial extension, loft conversion or structural opening without evidence of building regulations compliance may prompt a retention, a requirement for a specialist report, or a refusal to lend on the terms originally expected. Some lenders will accept a professional opinion that the works are structurally sound and unlikely to be subject to enforcement, but this is not guaranteed.

Buildings insurers may ask about alterations when a proposal form is completed. Non-disclosure can affect a claim, even where the omission was accidental. If the insurer discovers unapproved works after a loss, it may investigate whether the works contributed to the damage and whether the risk was fairly presented. Buyers should obtain confirmation of cover in writing before exchange where the alterations are significant.

When to Consult the Local Authority

Direct contact with the local authority can be valuable, but timing matters. A buyer may ask their solicitor to make formal enquiries rather than approaching the planning or building control department informally. A local authority can confirm whether it holds records, whether a completion certificate was issued, and whether any enforcement action is recorded. In some cases, a regularisation application may be possible, but this can require opening up works, commissioning a structural report and paying fees. The seller may not agree to that before exchange, and the buyer should understand who bears the cost and risk.

Pricing the Residual Risk Before Exchange

Once the evidence is assembled, the buyer should quantify the risk rather than describe it vaguely. Consider the likelihood of enforcement, the cost of regularisation or remedial work, the effect on mortgageability, the insurance position and the impact on resale. A structural engineer's report may be appropriate for load-bearing changes, while a solicitor can advise on contractual protections.

Practical options include asking the seller to obtain missing certificates or complete regularisation before completion, negotiating a price reduction that reflects the cost and uncertainty, holding a retention through the conveyancer, or requiring a specific indemnity policy with lender approval. Walking away remains a legitimate outcome where the evidence is thin and the works are material.

A Disciplined Approach

Unapproved alterations are not automatically a reason to abandon a purchase. They are a reason to slow down, request documents and price the uncertainty. In 2026, the prudent buyer should treat the absence of certificates as a gap in the property's history, not as proof that nothing can be done. With clear evidence, realistic advice and a negotiated position before exchange, many risks can be managed. The essential point is that the decision should be informed by documents and professional opinion, not by the reassuring appearance of finished bricks.