Extending in Horndean is mostly fine, except where it isn't. Twenty-eight listed buildings dot the wider area. Three conservation areas cover specific streets. Most houses sit outside both. The planning bill depends on which street you bought on.
Twenty-eight buildings in the wider area carry a listed status. None are Grade I. One is Grade II starred. The other twenty-seven are Grade II. Listed status means any change to the fabric of the building, internal or external, needs listed building consent on top of any planning consent. That covers windows, doors, chimneys, internal walls, fixtures, and anything else the inspector considers part of the special interest. The penalty for skipping the process is the council requiring you to put it back the way it was at your own cost, which is the kind of letter that ages a project quickly.
Three conservation areas sit in the catchment: Horndean itself, plus Catherington and Blendworth in the surrounding area. Conservation-area status doesn't ban changes. It does mean the planning department has a louder voice on materials, on tree work, and on the appearance of street-facing elevations. Demolition usually needs explicit consent. Replacement windows can require a like-for-like specification rather than a free choice. The conservation officer is generally the person whose opinion matters more than the planning officer's, and they tend to have firm views about how a Victorian or post-Victorian street should look. Households inside the boundary live with that. Households a few streets outside it generally don't.
For most Horndean homes, the standard permitted-development rules apply. A single-storey rear extension within the size limits, a loft conversion that stays under the dimensions, a porch that respects the height and footprint caps. None of those usually need a full planning application, and the village's post-war housing stock is largely outside the listed register and outside the three conservation boundaries. Anything bigger than the permitted thresholds, anything visible from the street in a conservation area, and anything touching a listed building needs a proper application. The volume of applications running through the local planning system gives a sense of the pace. Around 1,400 applications have been logged in the wider catchment over the most recent two-year window, with about 700 of those in the last twelve months. The system is busy, which suggests most owners are getting on with their projects rather than being deterred by them.
Horndean's planning system is averagely friendly to the homeowner. Most houses extend without a fight. A few streets answer to the conservation officer first and the architect second.