Selling a house where the extension has no paperwork

If you have no paperwork for an extension and you are about to market the house, the question the buyer's conveyancer will ask is narrow: show me the planning permission or a certificate, and show me the building regulations completion certificate. Those are two different documents from two different regimes, and an extension can be perfectly lawful in planning terms while having no building control sign-off at all.

Deal with it before the house goes on the market. A title enquiry answered in week three of a sale, with the buyer's mortgage offer waiting, is the point at which sensible options narrow to the expensive one.

What a buyer's conveyancer will ask for

Standard property enquiries ask for evidence of consents for any alteration, and lenders' requirements follow them. The usual list is planning permission or a lawful development certificate, building regulations approval and completion certificate, any listed building consent, and confirmation that conditions were discharged.

Where a homeowner replies that the work was permitted development, the conveyancer will want that demonstrated rather than asserted. Permitted development produces no document by itself, which is exactly why the certificate route exists.

Three practical answers exist: a certificate of lawfulness, a building control regularisation certificate, and indemnity insurance. They do different jobs and they interact badly, so choose before you act.

Whether the work was permitted development at the time

Start here, because everything else depends on it. Permitted development rights are set out in Schedule 2 to the General Permitted Development Order 2015, and the limits that applied are the limits in force when the work was carried out. Earlier orders had different depths, different heights and different rules on materials.

Work through the actual constraints of the property rather than the generic limits:

1. Was the property in a conservation area, National Park or National Landscape at the time, which narrows householder rights.
2. Is the building listed, which takes internal and external alterations into a separate consent regime entirely.
3. Did an Article 4 direction remove the relevant right in that street.
4. Did a condition on an earlier permission remove permitted development rights for the estate or the plot.
5. Had the original dwellinghouse already been extended, since most householder allowances are cumulative from the dwelling as originally built.
6. Does the extension sit within the curtilage as it was, rather than on land added to the garden later.

The last two catch people most often. Our note on measuring curtilage and the enlarged garden covers the second, and where a listed building is involved the position is tighter again, as our note on permitted development rights in a listed building curtilage explains.

Certificate of lawfulness as the formal answer

A certificate of lawful existing use or development, applied for under section 191 of the Town and Country Planning Act 1990, is the only formal way to confirm that works are lawful. It is decided on evidence and law, not on planning merits, so the council cannot refuse it because it dislikes the extension.

Two grounds are available. Either the works were permitted development when carried out, or they were unauthorised but are now immune from enforcement because of the passage of time.

The application needs drawings of what exists, a description of the works, and the evidence that supports the ground relied on. A fee is payable and it is indexed, so check the current fee schedule on the Planning Portal before you budget. Determination is normally eight weeks.

A granted certificate is the cleanest outcome for a sale. It is a public document, it satisfies lenders, and it does not expire.

Building control regularisation as a separate item

Planning lawfulness says nothing about construction standards. Where an extension was built after 11 November 1985 without a building control application, the council can issue a regularisation certificate under the Building Regulations 2010 once it is satisfied the work complies.

That usually means opening up: exposing foundations at an inspection pit, uncovering a lintel, or providing calculations for a steel. The council charges a regularisation fee, and the work required to demonstrate compliance is at your cost. For work carried out before November 1985 the regularisation route is not available, and a lender will generally accept the age of the work instead.

Building control enforcement and planning enforcement run on different clocks. Do not assume that time which cures a planning breach has cured a building regulations one.

Indemnity insurance and what it does not cover

Indemnity insurance is a financial product, not a consent. A policy typically covers the loss the owner would suffer if the local authority took enforcement action over the absence of consent, subject to the policy terms.

Three limits matter. It does not make the work lawful. It does not cover defective or unsafe construction, so it is no answer to an absent building control certificate where the concern is structural. And it is usually voided by any approach to the council about the property, which means you cannot apply for a certificate and insure the risk as well.

That last point forces the choice. If the evidence for a certificate is strong, apply for the certificate. If the evidence has gaps and the risk is remote, insurance may be the pragmatic route, but it is the buyer's solicitor who decides whether their client accepts it.

Enforcement time limits and their effect

Time limits have changed. Historically, operational development such as an extension became immune after four years, and most changes of use after ten. The Levelling-up and Regeneration Act 2023 moved England towards a single ten-year period, with the earlier limit continuing to apply to breaches that were already complete before the change took effect.

So the date the work was substantially completed decides which limit applies to it. Check the commencement and transitional provisions rather than relying on a general statement, because the answer for a 2019 extension differs from the answer for a 2025 one.

Immunity also does not arrive automatically. It has to be proved on the balance of probabilities by the person asserting it, and the proof is the evidence file described below.

Evidence that establishes the date of the works

Assemble more than you think you need. A single source rarely persuades.

Dated photographs with metadata, aerial imagery, the builder's invoices and quotations, bank statements showing the payments, the skip hire or scaffold invoices, delivery notes for materials, correspondence with a designer, insurance schedules showing the increased rebuild value, and council tax banding records all help. So do statutory declarations from the owner and from neighbours who can say when the work happened and that it has been there continuously since.

The word continuously matters. An extension built ten years ago, demolished and rebuilt five years ago, starts its clock again.

Where the extension triggered a Community Infrastructure Levy liability that was never declared, deal with that separately before applying for anything, and our note on CIL liability and permitted development sets out where that can arise.

Preparing the file before marketing

Start eight to twelve weeks before you list. Order the file, decide the route, and make the application if one is needed.

A Planning Statement setting out the works, the rights relied on, the constraints checked and the evidence relied upon turns a pile of receipts into something a case officer can determine. Councils refuse certificates for want of clear evidence more often than for want of merit.

Illustrative example: a single-storey rear extension built in 2016 on an unconstrained semi-detached house, 3.5 metres deep, 3 metres high with a flat roof, well inside the householder limits then in force. The owner has no permission because none was needed. A section 191 certificate application with drawings, dated photographs and the builder's invoice resolves the sale enquiry for the cost of the fee and a set of measured drawings. The missing building control certificate is dealt with separately by regularisation, with an inspection pit dug in the garden.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.

Enter your postcode on PlanScope to see which documents a certificate application for your extension is likely to need.