West Cornwall · TR13
House Extensions in Porthleven
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 Porthleven, that work is shaped by the place itself — Porthleven is the most southerly port on mainland Britain, AONB-designated, with a working harbour, dramatic winter swell and a terraced cliff-edge of Victorian cottages, with a building stock that leans toward fishermen's cottages above the harbour and Victorian terraces.
- Conservation Area
- Cornwall AONB
- Coastal exposure zone
Local context
Why Porthleven is its own job.
Porthleven Conservation Area covers the harbour and most residential streets; AONB designation extends across the whole parish. Coastal exposure and views from the South West Coast Path are routine planning considerations. For extension specifically, parts of Porthleven 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; coastal salt-laden air around Porthleven drives detailing choices — fixings, render systems and timber treatments all need to be specified for exposure. That's why we treat every Porthleven project as a TR13-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 Porthleven.
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.
Our process
How a Porthleven 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
Porthleven Extensions — common questions.
- 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 Porthleven specifically, we'd start by checking the Conservation Area boundary before committing to a direction.
- 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 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.
- 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.
Other services in Porthleven
Nearby places we cover