South Cornwall · PL25
One studio for extension in Charlestown
Extensions are the bread and butter of Cornish homes — adding the kitchen-diner the original layout never had, the bedroom for a growing family, or the light and views the back of the house should always have had. Charlestown sits in South Cornwall, and that geography ends up in the drawings — Charlestown is a Georgian-planned harbour village south of St Austell, World Heritage designated for its china clay shipping history, with tall ships still moored in the harbour, with a building stock that leans toward modern carefully matched coastal homes and Georgian harbour cottages.
Charlestown sits in South Cornwall — covering PL25 from St Austell outward.
- Conservation Area
- Cornish Mining World Heritage Site
- Coastal exposure zone
- ✓ One studio — design, planning and build under one roof
- ✓ Local to South Cornwall — not a national franchise
- ✓ Fixed-fee planning packages, no surprise invoices
- ✓ Measured-survey accuracy from day one
Our process
How a Charlestown extension project runs.
Step 1
Brief
We meet on site, talk through how you live now and what's missing from the current layout.
Step 2
Design
Two or three sketch directions with rough budgets, then refinement of the chosen route.
Step 3
Approvals
Planning or Cert of Lawfulness, then a full building regs package.
Step 4
Build
Either through your own builder with our drawings, or as a full build by our team.
Step 5
Handover
Snag, certify, hand over the keys to your new space.
Typical single-storey rear extensions run twelve to twenty weeks on site; two-storey and wraparound projects sixteen to thirty weeks.
Local proof — Most Charlestown extension clients we work with are second-time builders — they've seen the templated approach fail once already.
Get a free feasibility viewWhat we focus on
Extensions considerations specific to Charlestown.
01
Drainage on older Cornish properties is rarely on a clean modern map; CCTV survey before design is often money well spent.
02
Permitted development for rear extensions runs to four metres on a detached house, three on a semi or terrace — but Article 4 areas remove this in some parishes.
03
Extensions over a certain proportion of the original house trigger full Part L upgrade obligations to the existing building — worth knowing before brief is set.
04
Cornish granite and slate-hung walls react differently to new openings than modern brickwork — lintel choice and structural sequencing matter.
Local context
Why Charlestown is its own job.
Two things shape a Charlestown application: parish character and policy. On policy — conservation Area covers the entire historic harbour; World Heritage Site status applies. The Charlestown Estate operates a strong design code on materials and layout. For extension specifically, parts of Charlestown sit within a designated Conservation Area, which means materials, fenestration and roof pitches all need to read sympathetically with the existing streetscape; the wider area forms part of the Cornish Mining World Heritage Site, which adds a heritage assessment layer to most material changes; coastal salt-laden air around Charlestown drives detailing choices — fixings, render systems and timber treatments all need to be specified for exposure. Get that local reading right and the rest of the Charlestown programme tends to run on time. On modern carefully matched coastal homes in particular — the kind you'll also find toward St Austell — the extension brief always has to read the existing fabric first.
Planning note
Most extensions in Cornwall are either permitted development or a straightforward householder application — but Conservation Area and AONB sites need a more careful design conversation upfront.
Local watch-list
Charlestown-specific issues we screen on the first visit.
Watch #1
Conservation Area material and fenestration controls in central Charlestown
Watch #2
World Heritage Site assessment on changes visible in the mining landscape
Watch #3
Coastal exposure driving fixing, render and joinery spec
Charlestown is part of St Austell
Charlestown sits inside the St Austell catchment — we cover both as one extension territory.
See Extensions in St Austell →Local fabric
Charlestown extensions — the local-studio difference.
Building stock
Across Charlestown (PL25) we work on Georgian harbour cottages, Victorian villas, Edwardian houses, modern carefully matched coastal homes, converted clay-shipping warehouses. Each stock type drives a different extension response — modern carefully matched coastal homes in particular needs careful detailing here.
Parish & policy
Charlestown sits in the parish of St Austell, which matters for how parish-level consultation lands on a extension application.
Coverage
We cover PL25 from our studio, with regular extension jobs also running in St Austell. Most Charlestown site visits get booked within the same week.
Can you handle both planning and build in Charlestown?
Yes — design, planning, building regs and full construction run under one roof. For clients with an existing Charlestown builder we can stop at a tender-ready Full Plans pack instead.
Request a free visitWho this is for
Charlestown runs the full mix — owner-occupier, holiday-let, commercial and the occasional smallholding — so we scope every extension enquiry from the use-class up.
FAQs
Charlestown Extensions — local questions answered.
- How much does an extension cost in Charlestown?
- Build costs in Cornwall typically run from around £2,200 to £3,200 per square metre for a good-quality single-storey extension, more for kitchen-grade fit-out or complex glazing. We give a realistic budget before drawings start, not after. In Charlestown specifically, we'd start by checking the Conservation Area boundary before committing to a direction.
- Can you handle the build as well as the design?
- Yes — that's the whole point of the studio. One contract, one point of contact, no finger-pointing between architect and builder when something needs a decision on site.
- What about the Party Wall Act?
- If you share a wall with a neighbour or build close to a boundary, the Act applies. We flag it early, recommend a surveyor and keep the programme aligned with the notice period.
- Will my house be liveable during the build?
- For most rear and side extensions, yes — we sequence the works so the kitchen and one bathroom stay functional until the new build is watertight and connected.
- How long does the whole process take?
- Allow roughly three months for design and approvals, then twelve to twenty weeks on site for a typical single-storey extension. Wraparounds and two-storey add-ons take longer, mostly through approval and groundworks.
Other services in Charlestown
Nearby places we cover
Every Charlestown extension we work on is treated as a PL25 job in its own right — local fabric, local policy, local builders.