Selling a House After a Major Renovation

Selling a house that has been significantly renovated should, in theory, be straightforward — you have done the hard work of improving the property, and buyers should be willing to pay a premium for a well-finished home. In practice, however, renovation work introduces a layer of documentation that must be in place before the sale can proceed smoothly. Missing certificates, undisclosed planning history, and non-compliant work are among the most common causes of conveyancing delays in the UK.

This guide explains what buyers and their solicitors will expect, how to prepare your documentation, what to do if certificates are missing, and how to present your renovation in the best possible light to maximise the price you achieve.

Why documentation matters so much after a renovation

When you sell a property that has been altered or extended, the buyer is not just purchasing the bricks and mortar — they are also taking on any legal risk associated with the work that was done. Their solicitor's job is to identify those risks and either resolve them or ensure the buyer is aware of them before contracts are exchanged.

Mortgage lenders add another layer of scrutiny. Most high street lenders require evidence that structural work complies with building regulations before they will release funds. A buyer who cannot satisfy their lender's requirements cannot complete the purchase, which means the sale falls through — even if the work itself is of good quality.

Gathering your renovation documentation before you list the property — rather than hunting for it after an offer is accepted — is one of the most effective ways to protect your sale. See our overview of the documents needed to sell a house for a full checklist.

Documentation buyers will expect

The specific certificates required depend on the type of work carried out. The table below summarises the most common renovation types and the documentation buyers and lenders expect:

The buyer's solicitor will request all relevant certificates as part of the standard pre-contract enquiries. Delays in producing these documents are one of the leading causes of slow conveyancing.

How renovation work affects the TA6 form

The TA6 Property Information Form — the primary disclosure document in any property sale in England and Wales — contains a dedicated section (section 6) requiring sellers to disclose all alterations and building works carried out on the property. You must confirm:

• Whether any alterations, extensions, or additions have been made to the property
• Whether the works required planning permission and, if so, whether it was obtained
• Whether any conditions attached to a planning permission have been discharged
• Whether building regulations approval was obtained and whether a completion certificate was issued
• Whether any works were carried out under permitted development and, if so, whether a certificate of lawful development was obtained

The TA6 is a legal document. If you provide false or misleading information, the buyer can bring a claim for misrepresentation against you after completion, potentially for the cost of any remedial works or for the difference in value between what they paid and what the property was actually worth. Err on the side of full disclosure, even if it means disclosing that certain certificates are missing.

For more detail on completing the form correctly, see our guide to completing the Property Information Form.

What to do if certificates are missing

It is surprisingly common for sellers to discover that they cannot locate all the certificates for renovation work, particularly where work was done many years ago or by a contractor who did not provide paperwork. The approach you take depends on the type of certificate that is missing.

Missing building regulations completion certificate

If you cannot find a building regulations completion certificate for structural work, an extension, a loft conversion, or a garage conversion, you have two main routes:

1. Regularisation certificate. Apply to your local authority building control department for a retrospective approval. A building control officer inspects the work and, if it meets the regulations in force at the time it was carried out, issues a regularisation certificate. Costs typically range from £400 to £800. The process takes four to eight weeks and may require remedial work if deficiencies are found. See our dedicated guide on missing building regulations sign-off for a full walkthrough of this process.
2. Indemnity insurance. Purchase a one-off indemnity insurance policy covering the buyer and their lender against the risk of enforcement action by the local authority. Policies typically cost £100 to £300 and most lenders accept them provided the work was completed more than twelve months ago. The policy transfers to future buyers. Critically, do not contact the local authority building control department about the missing certificate before taking out the policy, as this can invalidate the insurance.

For a full explanation of both options, including when each is appropriate, see our guide on what to do without a building regulations certificate.

Missing FENSA certificate for windows

Replacement windows and doors installed since April 2002 should have a FENSA certificate. If you cannot find yours, search the FENSA online register at fensa.org.uk using the property address — the installation may be registered there even if you have lost the paper certificate. If the installer is no longer trading and the property does not appear on the register, indemnity insurance is the standard solution.

For a full guide on resolving this issue, see what to do without a FENSA certificate.

Missing planning permission

If you are unsure whether work required planning permission or whether it was obtained, your local planning authority can check their records. If the work was done more than four years ago (ten years for a change of use or breach of condition) the time limit for enforcement action has usually expired, and you may be able to obtain a certificate of lawfulness from the council confirming the development is now lawful. See our guide on checking planning permission before selling for a step-by-step explanation.

Capital Gains Tax and renovation costs

If you are selling a property that is not your main home — for example, a buy-to-let investment, a second home, or a property that you have renovated as a project — Capital Gains Tax (CGT) may be due on the profit. However, HMRC allows certain renovation costs to be deducted as allowable expenditure, which reduces the taxable gain.

What qualifies as allowable expenditure

Under Section 38 of the Taxation of Chargeable Gains Act 1992, allowable expenditure includes:

• Enhancement expenditure — costs incurred to improve the property and add value, such as building an extension, converting a loft, fitting a new kitchen, or installing a bathroom where there was none before. The improvement must still be reflected in the state or nature of the property at the time of sale.
• Incidental costs of acquisition and disposal— including estate agent fees, conveyancing costs, and stamp duty land tax paid when you originally purchased the property.

What does not qualify

Routine repairs and maintenance costs — such as redecorating, replacing a like-for-like boiler, or fixing a leaking roof — do not qualify as allowable expenditure. These are revenue expenses, not capital improvements. The distinction is not always obvious, and a tax adviser or accountant with property experience can help you identify which of your renovation costs are allowable.

Keeping records

To claim renovation costs as allowable expenditure, you need documentary evidence: invoices, receipts, bank statements, and contracts with contractors. Keeping these records from the outset is far easier than trying to reconstruct them at the point of sale. HMRC can ask to see evidence for up to twelve months after you submit your tax return.

Which renovations add the most value

Not all renovation work delivers the same return at the point of sale. The following improvements consistently rank among the highest value adds, according to RICS and estate agent data:

The key caveat with all of these figures is that they assume the work is fully documented and properly finished. A well-designed extension without building regulations sign-off will be valued at a discount compared to an equivalent extension with full documentation, because the buyer's lender may impose conditions or the buyer may factor in the cost of resolving the compliance issue.

For further guidance on how to position your property to achieve the best price, see our guide on how to get the best price for your house.

How to present renovation work to buyers

The way you communicate your renovation work — both in the property listing and during viewings — can have a meaningful impact on the price you achieve and the speed of the sale.

In the property listing

• Be specific about what was done and when. "Fully refurbished throughout in 2023" is more compelling than "recently renovated" and signals to buyers that the work is recent and likely still under any contractor warranties.
• Name the major works explicitly: "new kitchen (2022), new bathrooms (2022), rewired (2021), new combi boiler (2023)".
• Mention the documentation: "all works carried out with full building regulations sign-off and relevant certificates available" reassures buyers and their solicitors before they even instruct.
• Use professional photography. High-quality images that showcase finished renovation work — particularly kitchens, bathrooms, and new extension spaces — are particularly effective at justifying a premium price point.

During viewings

• Have a folder of documentation ready to show interested buyers: building regulations certificates, FENSA paperwork, Gas Safe certificates, and planning permissions. This builds confidence and differentiates your property from others where the documentation is unclear.
• Be prepared to explain what was behind the walls. Buyers who have commissioned a survey want to know that the renovation was done properly, not just cosmetically. Being able to talk about the structural engineer, the type of foundations used for an extension, or the specification of the insulation demonstrates that the work was done to a high standard.
• Mention any warranties still in force. A ten-year structural warranty on an extension or a manufacturer's guarantee on a kitchen is a tangible reassurance for buyers.

Common survey issues with recently renovated properties

Buyers who commission a homebuyer report (RICS Level 2) or a full building survey (RICS Level 3) will have the surveyor examine all recent work closely. Common issues flagged by surveyors on recently renovated properties include:

• Damp around new extensions. Poorly detailed junctions between a new extension and the existing structure are a common source of damp ingress. Surveyors inspect flashings, cavity trays, and the DPC (damp-proof course) at the junction.
• Inadequate fire safety on loft conversions. Missing or incorrectly specified fire doors, absence of interlinked smoke alarms, and non-compliant escape windows are frequently flagged issues.
• Structural movement near new work. Cracks in plasterwork, deflecting lintels, or differential settlement between new and old construction are all raised in survey reports.
• Non-compliant drainage connections. Drainage alterations that were made without the required approvals, or that do not comply with Part H of the Building Regulations, are increasingly common as open-plan extensions change the drainage layout of a property.
• Poor ventilation in newly insulated properties.Draught-proofing and insulation work done without adequate provision for ventilation can lead to condensation and mould. Surveyors flag this where double glazing or insulation has been added without trickle vents or mechanical ventilation.
• Cosmetic covering of underlying defects. Surveyors are trained to look behind fresh plasterwork, new flooring, and recent decoration for signs that underlying issues have been concealed rather than resolved.

Being proactive about these issues — by obtaining a pre-sale survey or commissioning an independent structural engineer's report before you market the property — can help you identify and address them before a buyer's surveyor does, reducing the risk of renegotiation.

A pre-sale documentation checklist for renovated properties

Work through this checklist before you instruct an estate agent:

1. Extension or structural work: Locate the building regulations completion certificate and, where required, the planning permission approval notice. If you cannot find them, speak to your solicitor about regularisation or indemnity insurance.
2. Loft conversion: As above, plus structural engineer's calculations and any Party Wall Agreement if the property shares walls with neighbours.
3. Windows and doors: Search the FENSA register for your property address and obtain replacement certificates if originals have been lost.
4. Boiler and gas work: Locate Gas Safe certificates for all gas work. Contact the installer or Gas Safe Register for replacements if needed.
5. Electrical work: Locate Electrical Installation Certificates. If the consumer unit was replaced or the property was rewired, check whether the work was registered with a competent person scheme (NICEIC, NAPIT, or similar).
6. Solid fuel stove: Locate the HETAS certificate or building control sign-off for the installation.
7. Garage conversion: Confirm building regulations sign-off is in place and check whether any permitted development rights were used or planning permission was required.
8. TA6 disclosure: Answer all questions in section 6 of the TA6 honestly and in full. Where certificates are missing, note what steps you have taken or are taking to address the gap.
9. CGT records: If the property is not your main residence, gather all invoices and receipts for improvement works to substantiate an allowable expenditure claim.

Sources

• Royal Institution of Chartered Surveyors (RICS) — Home surveys and valuation guidance — rics.org
• GOV.UK — Building Regulations 2010 (as amended) and Approved Documents — gov.uk/government/collections/approved-documents
• GOV.UK — Planning permission: when you need it — gov.uk/planning-permission-england-wales
• GOV.UK — Capital Gains Tax: what you pay it on, rates and allowances — gov.uk/capital-gains-tax
• HMRC — Allowable expenditure for Capital Gains Tax purposes, Taxation of Chargeable Gains Act 1992, Section 38 — legislation.gov.uk
• The Law Society — TA6 Property Information Form (4th edition) — lawsociety.org.uk
• FENSA — Fenestration Self-Assessment Scheme, online register — fensa.org.uk
• Gas Safe Register — Finding a registered engineer and certificate records — gassaferegister.co.uk
• HETAS — Solid fuel and biomass installer registration — hetas.co.uk
• Planning Portal — Permitted development rights for householders — planningportal.co.uk

Frequently asked questions