Penwith · TR20
New Mill extension — feasibility first, drawings second
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. On a New Mill site, the brief always meets the place — New Mill is a small rural hamlet in the TR20 area, with scattered homes, lanes and a deliberately quiet settlement pattern, with a building stock that leans toward small infill homes and converted barns.
New Mill sits in Penwith — covering TR20 from Penzance, Chyandour, Sancreed outward.
- Rural / open-countryside policy area
- ✓ Cornwall Council regulars across every sub-area
- ✓ Free first site visit, no obligation
- ✓ Plain-English feasibility before any drawings
- ✓ 30+ years of Cornwall Council approvals
Who this is for
New Mill 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 watch-list
New Mill-specific issues we screen on the first visit.
Watch #1
Tighter Local Plan tests on isolated rural dwellings
Local proof — Most New Mill homeowners come to us after a extension quote elsewhere felt vague on planning — we lead with feasibility instead.
Get a free feasibility viewFAQs
New Mill 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 New Mill 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.
Local context
Why New Mill is its own job.
Locally, 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. Which is why we scope New Mill projects parish-up, not template-down — the TR20 context shapes the design from day one. Whether the project is on small infill homes in the centre or further out toward Penzance, the extension response is locally tuned.
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 New Mill.
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
Drainage on older Cornish properties is rarely on a clean modern map; CCTV survey before design is often money well spent.
03
Wind and sea-spray exposure can drive material choices on west-facing extensions; we detail accordingly.
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 New Mill 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
Choosing a extension team that actually knows TR20.
Building stock
Across New Mill (TR20) we work on cottages, farmhouses, converted barns, bungalows, small infill homes. Each stock type drives a different extension response — small infill homes in particular needs careful detailing here.
Parish & policy
New Mill sits in the parish of New Mill, which matters for how parish-level consultation lands on a extension application.
Coverage
We cover TR20 from our studio, with regular extension jobs also running in Penzance, Chyandour, Sancreed. Most New Mill site visits get booked within the same week.
What does a first New Mill consultation cost?
Nothing. We come to the property, walk the site, talk through what works on a TR20 plot and follow up with a written feasibility note inside a week — no obligation either way.
Request a free visitNew Mill is part of Penzance
New Mill sits inside the Penzance catchment — we cover both as one extension territory.
See Extensions in Penzance →Other services in New Mill
Nearby places we cover
From initial feasibility to final handover, we manage extension projects across New Mill with careful attention to what makes Penwith unique.