Yes, you can extend most houses in Tollesbury, but in the old centre expect the council to have a say. The village has a few dozen listed buildings. The old core is a conservation area. Hundreds of planning applications go in every year. The clay under the village needs as much attention as the planners do.
Tollesbury has 32 listed buildings. None are Grade I, two are Grade II* and the other 30 are Grade II. If you own one, almost any change that affects its character needs listed building consent from Maldon District Council as well as any planning permission, and that covers inside work too, such as a staircase, a fireplace or an internal wall. Doing the work without consent is a criminal offence, so it cannot simply be sorted out when you sell. Only two buildings in the whole village are Grade II*, so the tightest controls apply to very few owners.
The village has one conservation area, covering the old centre and named after Tollesbury itself. Inside it, some changes that would normally go ahead without permission need a planning application, and the council will look closely at anything visible from the street. Before you commit to a house, check on the council's maps whether it is listed or inside the conservation area boundary, because the answer can differ between neighbouring houses on the same street.
People here are clearly altering their homes. Between April 2024 and June 2026, 1,119 planning applications were made in the area, 497 of them in the last twelve months. That tells you how much building work is going on. It does not tell you how many applications were approved. With that many applications going in, your neighbours are probably reading the planning list as closely as you are.
The ground also matters. The British Geological Survey puts shrink-swell risk across the area at class 3, and every postcode reaches that level. Shrink-swell means clay that swells when wet and shrinks when dry, so foundations can move with the seasons. For an extension, it means the foundations are likely to need to go deeper than usual, and a structural engineer should assess the ground before you finalise the plans. It is a routine part of building on clay and not a reason to give up on an extension, but it should be in the budget from the start.
On a house that is neither listed nor in the conservation area, a modest rear extension or loft conversion can often go ahead under permitted development, the standard rights that let you build within set limits without a planning application. Those rights shrink inside the conservation area and largely stop applying to a listed building. A semi on the edge of the village and a cottage in the centre are very different projects.
Tollesbury is middling on freedom to extend. Away from the historic core, you mainly need to deal with the clay. In the centre, the council and the conservation rules will shape what you build.