Knocking it down and starting again.

The householder rights in Part 1 of the permitted development order permit the enlargement, improvement or other alteration of a dwellinghouse. A building that replaces one is none of those three: it is a new dwelling, and new dwellings sit outside Part 1 entirely. Demolition can be a separate matter again, because taking a building down is itself development, although a dwellinghouse outside a conservation area is usually covered by the demolition right subject to prior approval of the method and the site restoration. In practice the demolition and the new house go into one full application, because a council assessing the replacement wants to see what is going and what is arriving in the same set of drawings.

Siting is a material consideration in its own right, so a better position for light, access, levels or privacy can be argued for and often granted. What changes the odds is where the case rests on the building being a replacement. In the countryside and in the Green Belt, part of what makes a replacement acceptable is that it sits broadly where the last one sat, so nothing new encroaches on open land. Move it into an untouched corner of the plot and the scheme starts to read as a new house in a new place, which is a much harder application. Inside a settlement boundary the constraint is far weaker and the ordinary tests of amenity, parking and character do the work instead.

This is settled by the courts rather than by statute, and it turns on the whole picture rather than on any single period of time. What councils and inspectors look at is the physical condition of the building and whether it is still capable of occupation, how long it has stood unused, whether any other use took over in the meantime, and what the owner's intentions have been over that period. A sound house left empty while an estate is settled is a very different case from a roofless shell in a field. Where there is any doubt at all, the right first step is a certificate of lawfulness establishing that the residential use survives, because every route on this page starts from that answer and an application that assumes it can fail on that ground alone.

The wording is in policy GB7 of the National Planning Policy Framework, rewritten in August 2026, which lists the replacement of an existing building among the forms of development that are not inappropriate in the Green Belt, provided the building is of permanent and substantial construction, is lawful in planning terms, and the replacement is for the same use and not materially larger than the one it replaces. What the Framework does not do is say how much larger is materially larger, and it never has. That figure comes from the local plan and it varies between authorities. Two things catch people out and both cut the same way: the comparison is with the original building rather than with the house as extended over the years, and volume is not floor area, so a tall building with an empty roof void holds far more of it than the house someone pictures in its place.

The levy is charged by some authorities and not others, and where it applies it is calculated on floorspace. Existing floorspace can be set against the new where the building has been in lawful use, which is often what makes a replacement affordable, but the test is strict and a long-empty building may not pass it. There is a self-build exemption for someone building their own home, and the government's guidance is explicit that it must be applied for and obtained before development commences. A commencement notice then has to be served, and failing to serve one in time attracts an automatic surcharge. These are the most expensive avoidable mistakes on this subject, because the relief cannot be granted retrospectively once the ground has been broken.

A permission for a replacement dwelling is a permission for one house, not two, and councils protect that with a condition. The common forms require the existing building to be demolished before the new one is occupied, or within a stated period after it. Either way the condition is what stops a replacement quietly becoming a second dwelling on the plot, and breaching it is a breach of the permission itself rather than a technicality. Where living on site through the build genuinely matters, the thing to raise at application stage is temporary accommodation, which is its own question with its own answer, rather than to assume the old house can stay standing.

Bats and their roosts are protected whether or not any bat is present at the time, and an older house with a roof void, hanging tiles or a chimney is exactly the kind of building they use. A preliminary roost assessment can be done at any time of year, but if it finds evidence the follow-up emergence surveys can only be done in a defined season, and missing that season costs a year rather than a month. Where roosts are confirmed the work proceeds under a licence from the statutory nature conservation body, with mitigation built into the new house, which is a normal and well-trodden route. The scheme rarely changes. The programme does, which is why the survey belongs at the start.