South Cornwall · TR3
Design, planning and build for Carnon Downs extension
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. What works on a TR3 plot rarely works elsewhere — Carnon Downs is a substantial residential village south of Truro on the A39, with a significant late twentieth-century estate expansion and a popular village school, with a building stock that leans toward individual self-build plots and modern Persimmon-style estates.
Carnon Downs sits in South Cornwall — covering TR3 from Devoran, Playing Place, Perranwell Station outward.
- ✓ Cornwall Council regulars across every sub-area
- ✓ Free first site visit, no obligation
- ✓ Fixed-fee planning packages, no surprise invoices
- ✓ Measured-survey accuracy from day one
Local proof — Our South Cornwall workload means a Carnon Downs extension project never has to wait for an out-of-county team to drive down.
Get a free feasibility viewLocal context
Why Carnon Downs is its own job.
Cornwall Council's lens on Carnon Downs is consistent: outside Conservation Area and AONB but in close proximity to AONB to the south. Feock parish operates active input on edge-of-village sites and infill. For extension specifically, Carnon Downs sits outside the headline designations, which usually gives a slightly more flexible starting point — but parish-level character still matters. That's why we treat every Carnon Downs project as a TR3-area job first — not a generic Cornwall job with a postcode bolted on. The individual self-build plots that dominate Carnon Downs (and continue out toward Playing Place) set the tone for any extension scheme here.
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.
What we focus on
Extensions considerations specific to Carnon Downs.
01
Wind and sea-spray exposure can drive material choices on west-facing extensions; we detail accordingly.
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.
Our process
How a Carnon Downs 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 fabric
Why Carnon Downs homeowners pick a local studio for extension.
Building stock
Across Carnon Downs (TR3) we work on 1960s and 1970s estates, modern Persimmon-style estates, individual self-build plots, older cottages on the village fringe. Each stock type drives a different extension response — individual self-build plots in particular needs careful detailing here.
Parish & policy
Carnon Downs sits in the parish of Feock, which matters for how parish-level consultation lands on a extension application.
Coverage
We cover TR3 from our studio, with regular extension jobs also running in Devoran, Playing Place, Perranwell Station. Most Carnon Downs site visits get booked within the same week.
How quickly can you visit a Carnon Downs site?
Usually within the same week. Carnon Downs (TR3) is on our regular South Cornwall run, alongside Devoran, Playing Place, Perranwell Station. First visits are free and you'll get an honest feasibility view inside seven days.
Request a free visitFAQs
Carnon Downs Extensions — local questions answered.
- 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. In Carnon Downs specifically, we'd start by checking the latest parish-level planning history before committing to a direction.
- Do I need planning permission for an extension?
- Often no — single-storey rear extensions, side extensions and modest two-storey additions can sit inside permitted development on a typical detached house. Conservation Areas, AONB and Article 4 zones remove some of those rights, so we always check the address first.
- 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.
- 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.
- How much does an extension cost in Cornwall?
- 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.
Carnon Downs is part of Devoran
Carnon Downs sits inside the Devoran catchment — we cover both as one extension territory.
See Extensions in Devoran →Other services in Carnon Downs
Nearby places we cover
Designing a extension in Carnon Downs is as much about reading the parish as reading the brief; we do both, and the planning outcomes follow.