Mid Cornwall · TR1
Treliske extensions — a Mid Cornwall studio
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 Treliske, that work is shaped by the place itself — Treliske is a town-edge neighbourhood in the TR1 area, where modern housing, larger gardens and edge-of-settlement plots create practical development opportunities, with a building stock that leans toward detached houses and bungalows.
Treliske sits in Mid Cornwall — covering TR1 from Truro, St Michael Penkivel, Calenick outward.
- Rural / open-countryside policy area
- ✓ Free first site visit, no obligation
- ✓ Plain-English feasibility before any drawings
- ✓ 30+ years of Cornwall Council approvals
- ✓ One studio — design, planning and build under one roof
Who this is for
Treliske 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
Local snags worth knowing before drawing a Treliske extension.
Watch #1
Tighter Local Plan tests on isolated rural dwellings
Local proof — Most Treliske extension clients we work with are second-time builders — they've seen the templated approach fail once already.
Get a free feasibility viewFAQs
Treliske Extensions — local questions answered.
- 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. In Treliske specifically, we'd start by checking the latest parish-level planning history before committing to a direction.
- 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.
- 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.
- 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.
Local context
Why Treliske is its own job.
The planning backdrop in Mid Cornwall is real, not abstract: neighbour amenity, highways, drainage and the transition from built-up edge to countryside are usually the planning pressure points. 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. Treat the TR1 parish brief as the design brief and the Treliske application has somewhere to land. Whether the project is on detached houses in the centre or further out toward Truro, 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 Treliske.
01
Wind and sea-spray exposure can drive material choices on west-facing extensions; we detail accordingly.
02
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.
03
Drainage on older Cornish properties is rarely on a clean modern map; CCTV survey before design is often money well spent.
04
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.
Our process
How a Treliske 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 Mid Cornwall studio is the right fit for Treliske extension.
Building stock
Across Treliske (TR1) we work on modern estates, bungalows, semis, detached houses, infill plots. Each stock type drives a different extension response — detached houses in particular needs careful detailing here.
Parish & policy
Treliske sits in the parish of Treliske, which matters for how parish-level consultation lands on a extension application.
Coverage
We cover TR1 from our studio, with regular extension jobs also running in Truro, St Michael Penkivel, Calenick. Most Treliske site visits get booked within the same week.
What does a first Treliske consultation cost?
Nothing. We come to the property, walk the site, talk through what works on a TR1 plot and follow up with a written feasibility note inside a week — no obligation either way.
Request a free visitTreliske is part of Truro
Treliske sits inside the Truro catchment — we cover both as one extension territory.
See Extensions in Truro →Other services in Treliske
Nearby places we cover
The extension jobs we're proudest of in Treliske are the ones where the planning route was clear before a single elevation was drawn.