The Best Way to Sell a House With an Unauthorised Extension

Planning permission vs building regulations

The first step is to identify exactly what is missing, because they are different things:

• Planning permission governs whether the extension was allowed to be built (size, appearance, use). Many extensions fall under permitted development, but larger ones need permission.
• Building regulations govern how it was built (structure, safety, insulation), evidenced by a completion certificate.

An extension can lack one, the other, or both. Your conveyancer and the local authority can confirm what consents exist, which determines the right fix.

Regularising the work

Regularising gives the cleanest title and the widest buyer pool, but it takes time and the council may require changes. It is worth it if the work is recent or you want the best price.

Indemnity insurance and time limits

For older unauthorised work, indemnity insurance is often the practical solution. Planning enforcement and building-regulations enforcement are generally time-limited, so after a number of years the council’s ability to act is restricted — an indemnity policy then protects the buyer and lender against the small residual risk, allowing a mortgage sale to proceed. As with covenants, do not approach the council about the specific work once you intend to insure, as that can invalidate the policy. Your conveyancer will advise on whether insurance is appropriate.

Disclosure and your duties

You must disclose unauthorised building work on the property information form — and it will surface in the buyer’s solicitor’s checks against planning and building-control records anyway. Provide whatever you have: any consents, the date the work was done, and any indemnity policy. Honest disclosure with a clear plan (regularisation or insurance) reassures buyers far more than an unexplained gap in the paperwork, and protects you from a post-sale claim for misrepresentation (see disclosure duties).

Selling fast despite unauthorised work

If regularisation is slow, the work is deterring mortgage buyers, or you need speed, a cash buyer will purchase with the issue disclosed, accept or insure the risk, and complete in 7-28 days without a lender to satisfy. Cash buyers and investors handle unauthorised extensions routinely. You disclose what you know, accept a price reflecting the issue, and gain a fast, certain sale. Related: restrictive covenants and expired planning permission.