Extension With No Building Regs? What Your Survey and Solicitor Will Say

There is a date buried in the Building Regulations that decides how much of a problem an unapproved extension really is. Regularisation — the process of getting retrospective sign-off from building control — only exists for work carried out on or after 11 November 1985. Before that date there is no route to a certificate at all, because the mechanism did not exist yet.

That single fact reframes most of these conversations. An extension with no building regulations approval is not one problem with one answer. It is at least three different situations, and which one you are in depends mostly on when the work was done and how it was built.

What “no building regs” actually means

Building regulations approval is separate from planning permission. Planning governs whether you were allowed to build the thing at all; building regulations govern whether it was built to an acceptable standard for structure, fire, insulation, drainage and ventilation. A great many extensions have one and not the other.

Approval leaves a paper trail. There should be an application, inspections, and a completion certificate at the end. When that trail is missing, the practical consequence is the one GOV.UK spells out plainly: without approval you will not have the certificates of compliance you may need when you want to sell your home.

Note what that does and does not say. It does not say the extension is dangerous. It does not say it fails the standard. It says nobody has ever certified that it meets it — and in a conveyancing transaction, an absence of evidence is treated as a risk to be priced or insured, not as a defect to be proved.

That distinction is the whole reason buyers get such contradictory advice on this. The estate agent says it happens all the time. The solicitor sounds alarmed. Both are right about their own part of the problem.

What your surveyor will and will not say

An RICS survey is not a compliance audit. Your surveyor is not checking the extension against Approved Document A line by line, and cannot certify it retrospectively — only a building control body can do that.

What a surveyor does is look at the thing itself and report what the construction tells them. On a Level 3 that means the visible structure, the junction between the extension and the original building, the roof covering and its detailing, evidence of movement or settlement at the join, ventilation to any enclosed roof void, drainage runs and gully positions, and whether the floor and wall build-up looks consistent with the era it was supposedly built in.

Some of the most useful findings are indirect. A flat roof with no visible ventilation, a soil pipe that appears to discharge into a surface water gully, a steel beam with no visible fire protection, or a step down into the extension that suggests a shallow floor build-up — none of those is proof of non-compliance, but each is a reason to press harder on the paperwork.

Our guide to what a surveyor actually inspects on an added-on room goes through that inspection in more detail. The short version: the survey answers “was this built properly”, not “was this built legally”.

What your solicitor does with it

The missing consent surfaces on the seller’s property information form, or when the solicitor asks for certificates and none appear. From there the conveyancing options are narrow and fairly standard.

The solicitor will usually raise the issue with the lender, because the lender’s requirements drive the outcome more than anyone’s preference does. Some lenders are relaxed about older unapproved work. Others want an indemnity policy in place before completion. A minority want the work regularised.

Two things are worth understanding before you form a view, because they are where buyers most often get caught out.

• Going down the regularisation route generally closes the indemnity one. Indemnity policies are typically written so that cover is unavailable once the local authority has been approached about the property — your solicitor will confirm the wording on the specific policy. Practically, that means you cannot try regularisation, dislike the answer, and fall back on insurance.
• Indemnity insurance does not fix anything. It covers you against enforcement action by the local authority. It does not pay to put right defective work, it does not make the extension compliant, and it does not protect you if the roof leaks in three winters’ time.

We are surveyors, not solicitors, and the choice between those routes is a legal one that belongs with your conveyancer and your lender. What we can tell you is which of them the physical evidence supports.

Indemnity insurance versus regularisation

There is a third option that people forget: negotiate. If the survey finds the extension is genuinely substandard rather than merely uncertified, that is a costed argument about price, not a paperwork exercise. Our guide to using survey findings to renegotiate covers how to put that case without losing the purchase.

The 11 November 1985 line

Regularisation is set out in regulation 18 of the Building Regulations 2010, and it applies specifically where “unauthorised building work has been carried out on or after 11th November 1985”. Work predating that has no regularisation route.

In practice, unapproved work from the 1970s or earlier is usually dealt with on the strength of its age. It has stood for decades, the local authority’s practical interest in it is remote, and lenders and insurers tend to treat long-standing work differently from something built last summer.

One nuance worth knowing if regularisation is on the table: the same regulation says a regularisation certificate is “evidence (but not conclusive evidence)” that the requirements have been met. It is a good outcome and it satisfies most lenders. It is not a guarantee that the extension is faultless, and it is not a substitute for having someone look at the building itself.

Building control may also require the work to be opened up for inspection before they will certify it. On an extension that has been plastered, tiled and lived in for fifteen years, that is not a trivial ask, and it is the reason many transactions land on indemnity instead.

What to do, in order

The sequence matters here more than in most survey findings, because one of the options closes the other.

• Establish when the work was done. Aerial imagery, council tax records, the seller’s own account and the construction detailing all help. The date determines whether regularisation is even available.
• Get the building inspected before you decide anything. If the extension is sound, the problem is administrative. If it is not, the paperwork is the smaller half of your problem. A Level 3 building survey is the appropriate level where structure and construction detail are the question.
• Tell your solicitor and your broker early. The lender’s stance is usually the deciding factor, and finding it out two days before exchange is how chains fall over.
• Do not contact the local authority yourself until you and your solicitor have agreed the route, because that call closes the indemnity option permanently.
• Read the survey alongside the legal advice, not instead of it. Our guide to handling a report that has found problems sets out how to weigh findings that need a specialist or a solicitor rather than a builder.

Most of these purchases complete. The extensions that stop a sale are the ones with a real structural or damp problem behind the missing certificate — which is precisely why the inspection is worth doing before the insurance question is settled, not after.

Reviewed and signed off by Blue Blossom Surveys. Published 27 October 2026. Last updated 27 October 2026. This article is general information about the survey side of an unapproved extension and is not legal advice — the consent question belongs with your conveyancer.