West Cornwall · TR20
House Extensions in Goldsithney
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 Goldsithney brief starts on the street, not the screen — Goldsithney is a small linear village on the B3280 inland from Marazion — and home to the Trademark Designs studio, so we know its lanes, water table and planning history personally, with a building stock that leans toward Victorian semis and modern infill and barn conversions.
Goldsithney sits in West Cornwall — covering TR20 from Marazion, Perranuthnoe outward.
- Rural / open-countryside policy area
- ✓ Fixed-fee planning packages, no surprise invoices
- ✓ Measured-survey accuracy from day one
- ✓ One studio — design, planning and build under one roof
- ✓ Local to West Cornwall — not a national franchise
Local watch-list
What usually catches extension projects out in Goldsithney.
Watch #1
Tighter Local Plan tests on isolated rural dwellings
Who this is for
Goldsithney 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 Goldsithney is its own job.
Outside the Conservation Area but the village fringes border the AONB; Perranuthnoe parish policy applies. Infill and barn conversion proposals dominate the parish planning workload. 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. So every Goldsithney job runs as a TR20-specific piece of work — local policy, local fabric, local builders. Most of our extension work in Goldsithney lands on Victorian semis, with detailing that has to nod to the wider Perranuthnoe 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 Goldsithney.
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
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
Wind and sea-spray exposure can drive material choices on west-facing extensions; we detail accordingly.
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 Goldsithney 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
Goldsithney 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 Goldsithney specifically, we'd start by checking the latest parish-level planning history 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.
- 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.
- 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.
Goldsithney is part of Marazion
Goldsithney sits inside the Marazion catchment — we cover both as one extension territory.
See Extensions in Marazion →Local proof — Most Goldsithney extension clients we work with are second-time builders — they've seen the templated approach fail once already.
Get a free feasibility viewOther services in Goldsithney
Nearby places we cover
For Goldsithney homeowners weighing up a extension, the right starting point is honest feasibility — that's what we lead with, before any drawings.