South Cornwall · PL24
Extensions Treesmill: PL24 planning, South Cornwall fabric
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 PL24 plot rarely works elsewhere — Treesmill is a small rural hamlet in the PL24 area, with scattered homes, lanes and a deliberately quiet settlement pattern, with a building stock that leans toward cottages and small infill homes.
Treesmill sits in South Cornwall — covering PL24 from Fowey, Golant, Bodinnick outward.
- Rural / open-countryside policy area
- ✓ 30+ years of Cornwall Council approvals
- ✓ Cornwall Council regulars across every sub-area
- ✓ Plain-English feasibility before any drawings
- ✓ Local to South Cornwall — not a national franchise
Local proof — Most Treesmill homeowners come to us after a extension quote elsewhere felt vague on planning — we lead with feasibility instead.
Get a free feasibility viewLocal context
Why Treesmill is its own job.
The main planning test is usually whether the proposal remains subordinate, locally detailed and acceptable on access, drainage and neighbour amenity. That sets the scene before any design work begins. 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. It's the kind of detail that decides whether a Treesmill application gets approved at eight weeks or stalls in committee. The cottages that dominate Treesmill (and continue out toward Bodinnick) 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 Treesmill.
01
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.
02
Cornish granite and slate-hung walls react differently to new openings than modern brickwork — lintel choice and structural sequencing matter.
03
Drainage on older Cornish properties is rarely on a clean modern map; CCTV survey before design is often money well spent.
04
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 Treesmill 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 South Cornwall studio is the right fit for Treesmill extension.
Building stock
Across Treesmill (PL24) we work on cottages, farmhouses, converted barns, bungalows, small infill homes. Each stock type drives a different extension response — cottages in particular needs careful detailing here.
Parish & policy
Treesmill sits in the parish of Treesmill, which matters for how parish-level consultation lands on a extension application.
Coverage
We cover PL24 from our studio, with regular extension jobs also running in Fowey, Golant, Bodinnick. Most Treesmill site visits get booked within the same week.
How quickly can you visit a Treesmill site?
Usually within the same week. Treesmill (PL24) is on our regular South Cornwall run, alongside Fowey, Golant, Bodinnick. First visits are free and you'll get an honest feasibility view inside seven days.
Request a free visitFAQs
Treesmill 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 Treesmill 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.
- 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.
- 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.
Treesmill is part of Fowey
Treesmill sits inside the Fowey catchment — we cover both as one extension territory.
See Extensions in Fowey →Other services in Treesmill
Nearby places we cover
Designing a extension in Treesmill is as much about reading the parish as reading the brief; we do both, and the planning outcomes follow.