East Cornwall · PL11
House Extensions in Seaton
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. A Seaton brief starts on the street, not the screen — Seaton is a holiday-coast settlement in the PL11 area, with strong second-home demand and exposed coastal building conditions, with a building stock that leans toward replacement dwellings and holiday lets.
Seaton sits in East Cornwall — covering PL11 from Looe, Duloe, Herodsfoot outward.
- Cornwall AONB
- Coastal exposure zone
- ✓ Measured-survey accuracy from day one
- ✓ One studio — design, planning and build under one roof
- ✓ Local to East Cornwall — not a national franchise
- ✓ Same team on paper as on site
Local watch-list
The PL11 constraints that shape a extension brief.
Watch #1
AONB landscape-impact scrutiny on visible elevations
Watch #2
Coastal exposure driving fixing, render and joinery spec
Who this is for
Seaton runs the full mix — owner-occupier, holiday-let, commercial and the occasional smallholding — so we scope every extension enquiry from the use-class up.
Local context
Why Seaton is its own job.
Planning scrutiny often focuses on visual impact, occupancy, parking, overlooking and whether replacement buildings respect the coastal edge. For extension specifically, 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 Seaton drives detailing choices — fixings, render systems and timber treatments all need to be specified for exposure. So every Seaton job runs as a PL11-specific piece of work — local policy, local fabric, local builders. Most of our extension work in Seaton lands on replacement dwellings, with detailing that has to nod to the wider Duloe streetscape.
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 Seaton.
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.
Our process
How a Seaton 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
Seaton Extensions — local questions answered.
- 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. In Seaton specifically, we'd start by checking AONB landscape sensitivity before committing to a direction.
- 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.
- 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.
Seaton is part of Looe
Seaton sits inside the Looe catchment — we cover both as one extension territory.
See Extensions in Looe →Local proof — Most Seaton homeowners come to us after a extension quote elsewhere felt vague on planning — we lead with feasibility instead.
Get a free feasibility viewOther services in Seaton
Nearby places we cover
For Seaton homeowners weighing up a extension, the right starting point is honest feasibility — that's what we lead with, before any drawings.