East Cornwall · PL15
Design, planning and build for Polyphant 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. A PL15 site visit comes before a Polyphant sketch, every time — Polyphant is a small rural hamlet in the PL15 area, with scattered homes, lanes and a deliberately quiet settlement pattern, with a building stock that leans toward converted barns and farmhouses.
Polyphant sits in East Cornwall — covering PL15 from Launceston, Warbstow, North Petherwin outward.
- Rural / open-countryside policy area
- ✓ 30+ years of Cornwall Council approvals
- ✓ Plain-English feasibility before any drawings
- ✓ Same team on paper as on site
- ✓ Fixed-fee planning packages, no surprise invoices
Local proof — Our East Cornwall workload means a Polyphant extension project never has to wait for an out-of-county team to drive down.
Get a free feasibility viewLocal context
Why Polyphant is its own job.
Cornwall Council's lens on Polyphant is consistent: the main planning test is usually whether the proposal remains subordinate, locally detailed and acceptable on access, drainage and neighbour amenity. For extension specifically, Cornwall Council's Local Plan applies tighter tests to isolated rural dwellings here, so design rationale and policy fit need to be set out clearly from the outset. That's why we treat every Polyphant project as a PL15-area job first — not a generic Cornwall job with a postcode bolted on. The converted barns that dominate Polyphant (and continue out toward North Petherwin) 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 Polyphant.
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
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 Polyphant 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 a East Cornwall studio is the right fit for Polyphant extension.
Building stock
Across Polyphant (PL15) we work on cottages, farmhouses, converted barns, bungalows, small infill homes. Each stock type drives a different extension response — converted barns in particular needs careful detailing here.
Parish & policy
Polyphant sits in the parish of Polyphant, which matters for how parish-level consultation lands on a extension application.
Coverage
We cover PL15 from our studio, with regular extension jobs also running in Launceston, Warbstow, North Petherwin. Most Polyphant site visits get booked within the same week.
How quickly can you visit a Polyphant site?
Usually within the same week. Polyphant (PL15) is on our regular East Cornwall run, alongside Launceston, Warbstow, North Petherwin. First visits are free and you'll get an honest feasibility view inside seven days.
Request a free visitFAQs
Polyphant 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 Polyphant specifically, we'd start by checking the latest parish-level planning history 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.
- 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.
- 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.
Polyphant is part of Launceston
Polyphant sits inside the Launceston catchment — we cover both as one extension territory.
See Extensions in Launceston →Other services in Polyphant
Nearby places we cover
Most Polyphant extension enquiries start with one honest conversation about what's actually allowed — and that conversation costs nothing.