Buying a House With No Planning Permission for the Extension: What to Check and What to Do

01

The Short Answer: Three Questions Decide Your Risk

Answer them in that order. A "no" to question 1 and a "no" to question 2 together mean the work is unauthorised and still open to enforcement. That is when the options later in this guide matter.

02

Step 1: Find Out What Was Actually Approved

Start with the paperwork rather than the seller's recollection.

1. The council's planning register. Search the address and look for decision notices, approved drawings and conditions. Our guides on checking the planning history of a property and finding approved planning drawings walk through it. Be aware that online records do not go back indefinitely: one council's search-information page says its online planning documents date back to 1995 and its decision notices to 1977, with older material available only by appointment (Hinckley & Bosworth Borough Council, CON29 Q1.1). Other councils differ.
2. The local authority search. Question 1.1 of the standard CON29 asks which of the following relating to the property have been granted, issued, refused or are pending: planning permission, listed building consent, lawful development certificates, building regulation approval, building regulation completion certificates and competent-person certificates (council reproduction of the CON29 form at the Hinckley & Bosworth page above; the Law Society says the 2016 form is available only through third-party suppliers: CON29 forms). Note what the answer tells you: it lists what the council holds on file. A blank does not mean the work was unlawful, because permitted development leaves no planning decision.
3. The seller's TA6 answers. The Law Society's TA6 (6th edition) notes say the Alterations section (questions 5.1 and 5.2) deals with planning permission, building regulations and competent-person certificates, and that sellers should hand their solicitor any planning permissions or building control consents they have. The 6th edition replaced the 4th and 5th editions, and has been mandatory for Conveyancing Quality Scheme firms since 30 March 2026 (Law Society).
4. Ask for the paperwork for each change. For every extension, loft or conversion, ask for the planning decision or lawful development certificate, and the building regulations approval and completion certificate. If something is missing, ask the seller's solicitor in writing when the work was finished, who did it, and whether the seller has had any contact with the council.

Keep a record of every answer. If a reply later proves wrong, the wording of the answer matters (see the FAQ on what the seller has to tell you).

03

Step 2: Did It Need Planning Permission at All?

Most householder extensions, loft conversions and outbuildings do not need an application if they fit within the permitted development rights in Schedule 2, Part 1 of the General Permitted Development Order 2015 (GPDO). Our permitted development guide covers the rights in full. For a buyer, the point is that "no planning permission" is often a fact about the paperwork, not a defect in the house. But the limits are tight, and a conveyancer should test the work against them.

Common limits on a rear or side extension (Class A, as at October 2026):

"Original" means the house as it stood on 1 July 1948, or as built if built after that date (GPDO art 2(1)). A previous owner's earlier extension therefore counts against the allowance. Lofts (Class B) are capped at 40 m³ of added roof space for a terraced house and 50 m³ for any other house, and may not extend beyond the roof slope on a principal elevation fronting a highway (Class B.1). These limits have not changed since 2019. The amendments made since then only change which converted homes can use Class A. The larger-extension rule in A.1(g) does not apply on land described in article 2(3) or on a site of special scientific interest.

Four ways permitted development can be lost, which are easy to miss:

• A planning condition. The GPDO does not permit development contrary to a condition on an earlier permission (art 3(4)). A new-build estate house may carry a condition removing permitted development rights. Government guidance says such conditions must identify precisely which rights are withdrawn, and that blanket removals are unlikely to meet the tests of reasonableness and necessity (PPG: Use of planning conditions). Read the decision notice rather than assume.
• An Article 4 direction. A council can withdraw specified permitted development rights across an area under article 4. A direction shows up in the local search, because CON29 Q3.9 asks about directions restricting permitted development. A planning condition is recorded in the decision notice, and conditions imposed by a local authority are a category of local land charge (Local Land Charges Act 1975 s1(1)(b)).
• Protected land. On land described in article 2(3) (National Parks, areas of outstanding natural beauty and conservation areas, among others) a house cannot use Class B for a loft extension at all (B.1(f)), and under Class A it cannot have a side extension, a two-storey rear extension or certain cladding (A.2).
• An unlawful base. Permitted development does not apply to work built on an existing building whose construction was itself unlawful (art 3(5)(a)). This matters if you plan to extend further: see the indemnity guide linked below.

How to prove it. The reliable proof that work was permitted development, or has become immune, is a lawful development certificate. Under s191 anyone can apply to the council for a certificate that an existing use or operation is lawful. If the council is satisfied, the lawfulness is "conclusively presumed" (s191(6)). A certificate for proposed work is available under s192. The fees are covered in our lawful development certificate guide.

A certificate only covers planning. Government guidance is explicit that granting one "does not remove the need to comply with any other legal requirements such as the Building Regulations 2010, or the Planning (Listed Buildings and Conservation Areas) Act 1990" (PPG: Lawful development certificates, answer to "How do lawful development certificates relate to other regulatory requirements?").

04

Step 3: Is It Immune From Enforcement?

If the work needed permission and did not get it, the next question is time. The rule changed recently, and it is where most older advice is wrong.

You may read that the council has only four years to act against an extension, "the 4-year rule". Since 25 April 2024 that is no longer the general rule in England. Section 171B of the Town and Country Planning Act 1990, as amended by section 115 of the Levelling-up and Regeneration Act 2023, now gives the council ten years, beginning on the date the operations were substantially completed (building work) or the date of the breach (a change of use of a building to a single dwelling). The old four-year period survives only through the transitional rule in regulation 5 of SI 2024/452: the amendments do not apply where the operations were substantially completed, or the change of use to a single dwelling occurred, before 25 April 2024.

That is not the same as "breaches before 25 April 2024". The test for building work is when it was substantially completed. Work started before that date but finished after it is on the 10-year clock. Government guidance sets the position out in the same terms (PPG: Enforcement and post-permission matters, para 17b-004).

The dates in the third column are arithmetic from the statute and are approximate by design, because the exact day depends on when the work was substantially completed, which is a question of fact. If a deal depends on the date, get evidence (dated invoices, building control records, photographs, aerial images) and let the council decide it through a lawful development certificate. On an existing-use application the applicant supplies the evidence, and the test is the balance of probability (PPG: Lawful development certificates, answer to "Who is responsible for providing sufficient information to support an application?").

Three things that stop the clock from protecting you:

• Earlier enforcement action. The council can take "further enforcement action" if, within the four years before it acts, it has already taken or purported to take action on the same breach (s171B(4)(b)). Government guidance says this covers an earlier notice that proved defective, and the case where an enforcement warning notice was issued within the time limit and further action is needed later (PPG time limits).
• Concealment. A council can apply to a magistrates' court for a planning enforcement order. The court may make one only if it is satisfied, on the balance of probabilities, that the breach was to any extent deliberately concealed, and that making the order is just (s171BC). The council then has an "enforcement year" to act even though the s171B period has run (s171BA); the application may be made within six months of the council getting evidence sufficient to justify it (s171BB). Government guidance also records that where there has been deliberate concealment, the courts have found the time limits do not engage until the breach is discovered, citing the Welwyn Hatfield and Jackson cases (PPG). For lawful development certificate purposes, the time for enforcement is treated as not having expired while the time to apply for a planning enforcement order is still open, or an application or order is current (s191(3A)).
• Listed buildings, and demolition in conservation areas. Neither has a limit. See the listed-building section below.

For how the time limits work in detail, see our guide to planning enforcement time limits. For the application route, see retrospective planning permission.

05

Can the Council Make Me Knock It Down After I Buy?

Yes, if the work is unauthorised, not yet immune, and the council decides enforcement is expedient. Three points from the statute explain why a change of owner does not help:

• An enforcement notice is served on "the owner and on the occupier of the land" and on anyone else with an interest materially affected (s172(2)). It must be served at least 28 days before it takes effect (s172(3)), and an appeal must be received before that date (s174(3)).
• If a step the notice requires has not been taken after the compliance period, "the person who is then the owner of the land is in breach of the notice" and commits an offence (s179(1)–(2)). The penalty is a fine; the section sets no cap, and the court must have regard to any financial benefit from the offence (s179(8)–(9)).
• A person charged who was not served with a copy of the notice has a defence of not being aware of it, but only where the notice is also not in the council's enforcement register under s188 (s179(7)). That is why the local search asks about notices: CON29 Q3.9 covers enforcement notices, stop notices, breach of condition notices, planning contravention notices and others, whether they subsist or the council has decided to issue them (reproduced at Hinckley & Bosworth).

A planning permission passes the other way. It "enure[s] for the benefit of the land and of all persons for the time being interested in it" (s75(1)), unless the permission itself says otherwise. So a lawful extension is yours to keep, and an unlawful one is yours to answer for.

What the search will not show. The questions as reproduced ask about formal notices and proceedings, not about informal complaints or open investigations: Q3.9 asks about notices, orders and proceedings, and Q3.8 asks only whether the council has authorised proceedings for a building regulations contravention (Hinckley & Bosworth reproduction, Q3.8). A formal notice, such as a planning contravention notice, does appear. The seller's TA6 answers on disputes and notices are the other place to look.

06

Planning Permission and Building Regulations Are Two Separate Problems

A house can have planning permission and no building regulations sign-off, or the reverse. A buyer should ask about both, and a lawful development certificate answers only the first.

• The completion certificate. A building control body gives a completion certificate once satisfied that the work complies, and it is "evidence (but not conclusive evidence)" of compliance (Building Regulations 2010 reg 17). Our guide to the building regulations completion certificate covers what to do if one is missing.
• The time limit. Under section 36 of the Building Act 1984, a council can serve a notice requiring the owner to pull down or alter non-compliant work. Until 1 October 2023 that notice could not be given more than 12 months after completion (section 36(4) as enacted). It is now 10 years, in force in England from 1 October 2023 (SI 2023/993, as annotated at section 36). The only saving is for notices given before that date (reg 7), so older work is now caught as well.
• No time limit for an injunction. Section 36(6) preserves the right of the building control authority "or any other person" to seek an injunction for removal or alteration, with no statutory time limit stated.
• Regularisation. If building work was done without a building notice or approved plans on or after 11 November 1985, the owner can apply for a regularisation certificate. The council may require the work to be opened up for inspection, and may specify work needed to comply (Building Regulations 2010 reg 18). It may give a certificate if satisfied. The certificate, like a completion certificate, is evidence but not conclusive evidence of compliance (reg 18(6)).

You may read that missing building regulations approval means you cannot buy or sell the house. I found nothing in the regulations or the Lenders' Handbook that makes a completion certificate a precondition of sale: regulation 17(4) treats it as evidence, and the Handbook rule for conveyancers (below) contemplates completing where the conveyancer can certify the title. What the gap does mean is that you are buying a risk of a section 36 notice for up to 10 years from completion, and the cost of opening up the work if you regularise.

07

Your Options: Who Does What

The fees come from the MHCLG fee schedule, which says an existing-use certificate costs the same as the full application fee and a proposed-use certificate half of it. Fees rise each 1 April by CPI. Government fee guidance lists "retrospective applications where development has already taken place" among the applications that carry a fee (PPG: Fees for planning applications).

Why the order matters. The two routes that involve the council can be the right fix, and they can also prompt the very enforcement the buyer fears. Two points follow.

• Neither a lawful development certificate nor a retrospective application is a free check. A retrospective application asks the council to decide on the merits, can be refused, and under NPPF policy DM8(2) intentional unauthorised development "should be given substantial weight" when deciding whether to grant permission. If an enforcement notice is issued after a related application for planning permission (a retrospective application, not a lawful development certificate application), the ground (a) appeal ("planning permission ought to be granted") is not available, unless the notice is issued more than two years after that application stopped being under consideration (s174(2A) and (2AB)). For work that was permitted development or is now immune, a certificate asks a different question, whether the work is lawful and not whether it is acceptable (s191(4)), and is usually the better route if you have the evidence.
• Settle the indemnity question before anyone writes to the council. The sample policy we reviewed contains a general condition that, without the insurer's written consent, you will not "communicate about an Insured Risk with a third party", and an exclusion for loss arising because you apply for retrospective building regulations approval without the insurer's prior written consent (Additional Exclusion 2) (CLS Risk Solutions / ERGO sample wording, 2016). That sample reproduces the building regulations risk; a planning policy will have its own appendix, so read the wording you are actually offered. The full position is in our guide to planning indemnity insurance.

08

What Your Mortgage Lender Needs

Lenders who use the UK Finance Mortgage Lenders' Handbook (England and Wales) give the borrower's conveyancer standard instructions. The Handbook is voluntary for lenders and not all use it. Part 1, paragraph 5.5.1, tells the conveyancer to take all reasonable steps by searches and enquiries to ensure that:

• the property has the benefit of any necessary planning consents (including listed building consent) and building regulation approval for its construction and any later change or current use;
• there is no evidence of breach of the conditions of any consent; and
• no matter is revealed that would preclude residential use or that the property may be the subject of enforcement action.

The paragraph continues: where there is evidence of a breach but, in the conveyancer's professional judgment, "no reasonable prospect of enforcement action", and the conveyancer is satisfied that the title is good and marketable and can give an unqualified certificate of title, the lender "will not insist on indemnity insurance". Under paragraph 5.5.2, if there is such evidence and outstanding conditions will not be satisfied by completion, a conveyancer who cannot give an unqualified certificate must report to the lender. Paragraph 5.5.3 sends the conveyancer to the lender-specific Part 2 to see whether copies of planning and building control documents must be sent. Where indemnity insurance is used, paragraph 9.2 requires, among other things, that it is arranged without cost to the lender and that its terms do not prejudice the lender's interests.

I could not open the Handbook's own pages directly, which block automated access; the wording above is from an archived copy of Part 1 captured on 6 March 2026 (Wayback Machine capture). Your conveyancer will work from the live text and your own lender's Part 2.

In practice, tell your broker and conveyancer about the issue early. Which fix a particular lender will accept, whether an indemnity policy, a lawful development certificate or something else, is set by that lender's own instructions in Part 2 of the Handbook.

09

Listed Buildings and Conservation Areas: Why the Risk Is Different

Listed buildings. It is an offence to execute works for the demolition of a listed building, or its alteration or extension in a way that affects its character, without listed building consent (LBCA 1990 s7; s9(1)). The penalty on summary conviction is up to six months' imprisonment or a fine, or both, and on indictment up to two years or a fine, or both (s9(4)). The council can issue a listed building enforcement notice (s38). The Law Society's TA6 notes put the buyer's position plainly: enforcement can be taken against the owner; "there are no time limits for enforcement action, and it doesn't matter whether the person was the owner when the breach was committed"; and "the buyer could face enforcement action for work carried out by a previous owner" (TA6 (6th edition) explanatory notes). Retrospective consent is possible, and the works are then "authorised from the grant of that consent" (s8(3)), which means from the date of the consent, not from when the works were built. Our guide to planning permission for listed buildings explains the consent system.

Treat unauthorised works to a listed house as a serious issue, not a paperwork gap. The sample indemnity policy we reviewed requires as a statement of fact that "the Property is not a listed building" (2016 sample wording, building regulations appendix), so do not assume insurance is available.

Conservation areas. Permitted development is narrower there (see Step 2). Demolition of an unlisted building in a conservation area is an offence under TCPA s196D if done without planning permission, and there is no time limit on enforcement for "relevant demolition" (s171B(2A)). You may read about "conservation area consent". Historic England says it was previously needed to demolish unlisted buildings in conservation areas, that since 2013 it is no longer required, and that planning permission is required instead for "relevant demolition" (Historic England). The offence provision was inserted by Schedule 17 to the Enterprise and Regulatory Reform Act 2013, in force from 1 October 2013 (SI 2013/2227 art 2(m), as annotated). See conservation areas and planning.

10

Annexes, Garage Conversions and Lofts Used as Bedrooms

• Annexes and outbuildings used as a separate home. Turning a building into a single dwelling is a change of use for s171B(2) purposes, so the 4-year and 10-year dates above apply to it, counted from the date of the change of use. Whether an outbuilding is ancillary or a separate dwelling is a question of fact, and the council tax position turns on physical features (next point). See our annexe guide.
• Council tax. The Valuation Office Agency says that any building or part of a building constructed or adapted for use as separate living accommodation must have its own banding, that only physical features count and not how the space is used, and that a separate band is still needed if the area is vacant (GOV.UK: how Council Tax bands are assessed). The Law Society's TA6 notes add that where alterations have been made since the last valuation, a sale may trigger a re-valuation that moves the house into a higher band (TA6 notes). Ask what the current band is, and whether it matches the accommodation.
• Garage conversions and lofts. Both involve planning and building regulations. A loft needs to fit Class B (see Step 2), and a garage conversion may breach a condition on the original permission (art 3(4), above). Our guides to loft conversions and garage conversions cover each. Ask for both the planning evidence and the completion certificate, because the second is the one most often missing.

11

Red Flags: When to Walk Away

None of these is a rule that you must withdraw, but each is a reason to stop and take advice before you are bound:

• The house is listed, and the seller cannot produce listed building consent for alterations or extensions.
• The work was finished on or after 25 April 2024 and needed permission: the 10-year clock will run until at least April 2034.
• The seller or agent says you must not contact the council, and nobody will explain the policy that requires it. That condition is a feature of some insurance policies; read it first.
• The work appears to breach a condition or a restriction on the permission (for example, an annexe condition tying it to the main house).
• Neighbours have complained (the seller's TA6 answers on disputes and notices should say so) or the council has issued a planning contravention notice.
• The lender or valuer has raised it and the conveyancer cannot certify title.
• The work was built to look like something else. Concealment can extend the time for enforcement (s171BA).
• There is no completion certificate, the work is substantial, and the owner will not let building control inspect it. Regularisation can require the work to be opened up for inspection (reg 18(3)), so budget for that.

If the work is immune or permitted development and a lawful development certificate is obtainable, the same facts can become a negotiating point rather than a reason to walk.

12

Wales, Scotland and Northern Ireland

This guide is about England. Do not apply England's rules elsewhere.

14

Check the Area Around the House Too

An unauthorised extension is a problem at the house. Neighbouring applications are a separate risk, and the searches handle them differently. PlanWatch's property planning report lists the planning applications around an address and matches earlier applications to the property itself, with a confidence rating, and PlanWatch alerts (a paid-plan feature) tell you when a new application is logged near a postcode, which is useful between offer and completion.