Extending a house in Hassocks is possible. Extending one without paying a specialist to hold your hand through the process is not, because the heritage density around here is unusually thick for a village. Roughly two hundred and eighty listed buildings sit inside the wider postcode. Seventeen designated conservation areas overlap it. A slice of the parish sits inside the South Downs National Park, which brings its own planning authority. What you can extend depends less on what you want and more on which of those overlays the surveyor draws over your title deed.
The listed-building count for the wider Hassocks postcode runs to around two hundred and eighty properties. Eight of those carry the top Grade I designation, which is the register's tightest category and covers buildings of exceptional interest. Another nineteen sit at Grade II star, which covers buildings of particular importance short of exceptional. The remaining two hundred and sixty are Grade II, the standard listing that still binds every material change. What listing means in practice is that most alterations to the fabric of the building require listed-building consent from the local authority, and consent is granted or refused on the basis of whether the change harms the special interest that got the building listed in the first place. Replacing a window with a modern version, changing a roof covering, altering an internal wall inside a room the surveyor thinks is important, or adding an extension that abuts the listed element: each one starts a paperwork chain that runs for months.
Conservation-area coverage is a separate layer and applies whether or not any individual house on a street is itself listed. The wider Hassocks postcode contains seventeen designated conservation areas across its constituent villages, including Ditchling, Hurstpierpoint, Keymer, Clayton, Fairfield, Hurst Wickham, Langton Lane, Pyecombe, Poynings, Albourne, and Streat, among others. Inside a conservation area, the default rights that let a normal householder change a window, add a small side extension, put up a modest fence, or clad a wall without asking permission are curtailed or removed. Any material change to the visible exterior of a building becomes a planning matter rather than an assumed right. The threshold a semi in an unconstrained postcode would slide under, a semi in a Hassocks conservation area walks into head-first.
For a house that is neither listed nor inside a conservation area, permitted-development rights still apply, which means a range of alterations, extensions, and outbuildings can go ahead without applying for full planning permission. That leaves most of the newer post-war stock in a workable position for a family who wants to add a rear extension or convert the loft. For anything older, anything sitting in one of the pretty village cores, or anything overlooking the escarpment inside the national park boundary, the calculation is different. The planning applications lodged in the wider area come in at around five hundred a year, which gives some idea of the volume of activity even under the constraints. What that number can't reveal on its own is how many get approved on the first attempt and how many are the same address coming back around after a redesign.
So can you extend a house in Hassocks? Yes, if you buy the right kind of house in the right kind of spot and accept that the design you build will be the design the planning officer approves rather than the design you sketched. One out of five on the freedom-to-alter scale, which is the polite way of saying the heritage that makes the village nice to look at is the same heritage that makes it hard to change.