North Cornwall · TR5
House Extensions in St Agnes
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. In St Agnes, that work is shaped by the place itself — St Agnes is a former mining village on the north coast with a strong artistic community, AONB and World Heritage designation, and dramatic coastal mining ruins (Wheal Coates) on its doorstep, with a building stock that leans toward miners' terraces and Victorian villas.
- Conservation Area
- Cornwall AONB
- Cornish Mining World Heritage Site
- Coastal exposure zone
Local context
Why St Agnes is its own job.
Conservation Area covers Vicarage Road, Town Hill and the church area. AONB, Heritage Coast and World Heritage Site designations across the parish. Mining heritage shapes most planning conversations. For extension specifically, parts of St Agnes sit within a designated Conservation Area, which means materials, fenestration and roof pitches all need to read sympathetically with the existing streetscape; the surrounding landscape falls inside the Cornwall Area of Outstanding Natural Beauty, so massing, height and landscape impact carry extra weight in any planning decision; 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 St Agnes drives detailing choices — fixings, render systems and timber treatments all need to be specified for exposure. That's why we treat every St Agnes project as a TR5-area job first — not a generic Cornwall job with a postcode bolted on.
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 St Agnes.
01
Cornish granite and slate-hung walls react differently to new openings than modern brickwork — lintel choice and structural sequencing matter.
02
Wind and sea-spray exposure can drive material choices on west-facing extensions; we detail accordingly.
03
Drainage on older Cornish properties is rarely on a clean modern map; CCTV survey before design is often money well spent.
Our process
How a St Agnes 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.
FAQs
St Agnes Extensions — common questions.
- How much does an extension cost in St Agnes?
- 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 St Agnes 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.
Other services in St Agnes
Nearby places we cover