Yes, and in Great Leighs that is easier than in most older Essex villages. There is no conservation area. There are 17 listed buildings, every one of them at the lowest grade. The clay underneath matters more than the heritage rules. For most houses, the main limits are ordinary planning rules and the ground they stand on.
Great Leighs has 17 listed buildings: 0 at Grade I, 0 at Grade II*, and all 17 at Grade II. Listing at any grade means listed building consent for changes that affect the building's character, inside as well as out, and replacing windows or knocking through a wall can need it. For the other homes in the village, which is nearly all of them, the heritage system has nothing to say. The parish appears in the Domesday Book of 1086, and in the centuries since it has collected 17 listed buildings.
People round here do alter their homes. The planning records for the wider area around the village logged 2,215 applications between April 2024 and June 2026, 1,008 of them in the last twelve months. Those figures cover more than Great Leighs, and an application on file shows that someone wanted to build, not that permission came through. Even so, there is plenty of building going on, which is reassuring for a buyer until the scaffolding goes up next door.
The ground is the bigger consideration. The British Geological Survey puts Great Leighs in shrink-swell class 3, and 100% of the area reaches that class. Shrink-swell describes clay that swells when wet and shrinks when dry, moving whatever is built on it. For an extension, that usually means deeper foundations than on sandy or chalky ground, and a structural engineer's view where trees or large shrubs are near the new walls. Building control will ask about it, and so will the insurer. The clay will make its own decision about your foundations, whatever the planning officer allows.
Outside the 17 listed buildings and without a conservation area, an ordinary house in Great Leighs keeps the standard permitted development rights. Modest rear extensions, many loft conversions and most outbuildings can go ahead without a full planning application, provided they stay within the national size limits. Flats have no such rights, and building regulations apply either way. Newer estates are the exception to check. Councils sometimes remove permitted development rights through conditions on the original estate permission, and Chelmsford City Council's planning records will show whether a particular house was built under one. A conservatory that would need no permission on one close can need a full application on the next.
Freedom to extend is one of Great Leighs' real strengths. With almost nothing listed and nothing protected by a conservation area, the planning rules leave most owners alone, and the clay is the part that needs planning for.