Planning a Home Extension in Wiltshire: What to Think About Before You Start
An extension is one of those decisions that sounds straightforward until you start looking into it. A bit more space. A better kitchen. Somewhere for the children to spread out. The idea arrives fully formed, and the practical questions follow afterwards, often all at once.
If you are at that stage, thinking about extending your home somewhere in south Wiltshire but not quite sure where to begin, this guide is for you. Not a checklist, and not a list of regulations to memorise. Just the things we think are genuinely worth working through before you take the first formal step.
Start with what you actually want the space to do
It sounds obvious, but it is the question most often skipped. People tend to begin with the shape of the extension (single storey, double storey, side return, rear) rather than the life they want to live inside it.
Before you commit to a design, spend some time with the real question. Are you trying to solve a specific problem, like a cramped kitchen or a lack of a downstairs loo? Are you preparing for a change in how the household uses the home, a new baby, an elderly parent moving in, teenagers who need somewhere that is not the sofa? Are you thinking about eventual resale value, or is this the house you plan to grow old in?
The answers matter because they shape everything that follows. A family building their forever home will make different choices to one planning to sell in five years. A kitchen extension designed around how you actually cook looks nothing like one designed from a floor plan alone.
Work out a realistic budget, then add a buffer
Extension costs in Wiltshire vary enormously depending on size, specification, and the existing structure you are building against. Rather than quote ballpark figures that could mislead you, the honest answer is that a proper quote from a builder who has walked through your home will always beat a number pulled from an online calculator.
What we can say is this. Whatever budget you land on, hold a contingency back. Ten percent is the bare minimum. Fifteen is safer. Older homes especially have a habit of revealing surprises once work begins, and you want the ability to respond to those without the project stalling.
Be careful too of quotes that come in noticeably lower than the others. In construction, a price that looks too good usually is, and the gap tends to reveal itself later in the form of variations, upgrades, and costs that were never included in the first place. Transparent, line-by-line pricing from the outset is worth a great deal more than a low headline number.
Understand what planning permission actually involves
Many extensions in Wiltshire can be built under Permitted Development rights, which means full planning permission is not required. The rules are specific though, and they cover things like how far an extension can project from the rear of the house, maximum heights, and what proportion of the garden can be built on.
There are two important caveats. The first is that Permitted Development rights are restricted or removed entirely in conservation areas, Areas of Outstanding Natural Beauty, and on listed buildings. Much of south Wiltshire falls into one or more of these categories. The second is that even where Permitted Development applies, you will usually want a Lawful Development Certificate from Wiltshire Council to confirm it, which takes time and costs a small fee.
If your extension does need full planning permission, expect the process to take around eight weeks from submission, assuming no complications. Pre-application advice from the council is available and often worth the cost, particularly for anything on a listed or near-listed property.
A good builder will have worked through this process many times and will know what is likely to fly locally. It is one of the things worth asking about in a first conversation.
Think about the people living next door
Extensions do not happen in isolation. Your neighbours will notice, and how a project affects them matters, both for your relationship with them and, sometimes, for the planning process itself.
Party Wall agreements may be required if you are building close to or on a shared boundary. These are legal notices that need to be served correctly and in good time. Beyond the formal requirements, there is the simple reality of living next to a building site for several months. Noise, dust, deliveries, the occasional early start. How your builder manages all of that makes a real difference to the people around you.
At James Burton Construction, the impact on neighbouring properties is something we think about throughout every project. Considerate management of deliveries, noise, and site tidiness is built into how we work, because we know your relationship with the people next door needs to survive the build.
Build a realistic timeline
A straightforward single storey extension in Wiltshire typically takes around ten to sixteen weeks on site, depending on size and finish. Double storey extensions run longer, often sixteen to twenty-four weeks. Add to that the time needed for design, planning, tender, and preparation before work begins, and most extensions are a six to nine month commitment from first conversation to moving back into the space.
That may sound like a long time. It is worth remembering that the early stages (getting the design right, pricing the job properly, making sure everything is in place before the first tool comes out of the van) are where most of the money is saved and most of the stress is avoided. Projects that race to start on site tend to pay for it later.
Choose a builder you can actually talk to
This is the single most important decision in the whole process, and it deserves more attention than it usually gets.
Qualifications, insurance, and references matter. They are the minimum, though, not the measure. What matters beyond that is whether you can have a real conversation with the person in charge, whether questions get answered honestly, and whether you feel looked after when things get complicated (which, at some point, they will).
At JBC, every client has a dedicated project administrator from day one. A named point of contact, based in our office, whose job is to be there for you. No chasing site teams for updates. No wondering who to call. It is one of the things we are proudest of, and one of the things clients most often mention when they recommend us to someone else.
Ready to talk it through?
If you are thinking about an extension somewhere in south Wiltshire and would like to have a proper conversation about what is possible, we would be glad to hear from you. No obligation, no pressure, just a chance to talk through your ideas and get a sense of what the project might really involve.
Call the office on 01725 557591 or drop us an email at office@jamesburtonconstruction.co.uk.
