West Cornwall · TR19
House extension costs in Mousehole — what TR19 homeowners actually pay
Most Mousehole cost questions land in the same bracket: a single-storey rear sits roughly £2,200–£2,800/m² built, a two-storey side runs £2,000–£2,500/m², and anything touching a coastal elevation tends to add 8–12% for materials and detailing. We quote on measured drawings, not guesses. 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 Mousehole site, the brief always meets the place — Mousehole is a famously photogenic fishing village south of Newlyn, almost entirely within the Conservation Area and AONB, with a tiny harbour and dense lanes of granite cottages, with a building stock that leans toward granite fishing cottages and converted net-lofts.
Mousehole sits in West Cornwall — covering TR19 from Newlyn, Paul outward.
- Conservation Area
- Cornwall AONB
- Coastal exposure zone
- ✓ Typical Mousehole single-storey rear: £55k–£85k build cost
- ✓ Two-storey side extension: £85k–£140k build cost
- ✓ Wrap-around / L-shaped: £110k–£180k build cost
- ✓ Design + planning + building regs fee from £4,800 (fixed)
Local proof — Most Mousehole extension clients we work with are second-time builders — they've seen the templated approach fail once already.
Get a free feasibility viewLocal context
Why Mousehole is its own job.
Locally, almost the entire village is within both the Conservation Area and AONB; new openings, dormers, render colours and roof materials all attract close scrutiny. Paul parish operates with strong policy resistance to second-home use. For extension specifically, parts of Mousehole sit within a designated Conservation Area, which means materials, fenestration and roof pitches all need to read sympathetically with the existing streetscape; the surrounding landscape falls inside the Cornwall Area of Outstanding Natural Beauty, so massing, height and landscape impact carry extra weight in any planning decision; coastal salt-laden air around Mousehole drives detailing choices — fixings, render systems and timber treatments all need to be specified for exposure. Which is why we scope Mousehole projects parish-up, not template-down — the TR19 context shapes the design from day one. Whether the project is on granite fishing cottages in the centre or further out toward Paul, 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 Mousehole.
01
Cornish granite and slate-hung walls react differently to new openings than modern brickwork — lintel choice and structural sequencing matter.
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 Mousehole 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 Mousehole homeowners pick a local studio for extension.
Building stock
Across Mousehole (TR19) we work on granite fishing cottages, Victorian villas above the village, modern infill carefully matched to traditional vernacular, converted net-lofts. Each stock type drives a different extension response — granite fishing cottages in particular needs careful detailing here.
Parish & policy
Mousehole sits in the parish of Paul, which matters for how parish-level consultation lands on a extension application.
Coverage
We cover TR19 from our studio, with regular extension jobs also running in Newlyn, Paul, Penzance. Most Mousehole site visits get booked within the same week.
What does a first Mousehole consultation cost?
Nothing. We come to the property, walk the site, talk through what works on a TR19 plot and follow up with a written feasibility note inside a week — no obligation either way.
Request a free visitFAQs
Mousehole Extensions — local questions answered.
- What's the average cost of a single-storey extension in Mousehole?
- For a typical 20–30m² rear extension in Mousehole (TR19) we'd expect £55k–£85k including VAT, depending on glazing spec and whether the kitchen is being reworked. Coastal exposure here pushes weather-tightness specs up, which is real money.
- Do extension costs in Mousehole include planning and building regs?
- Our fixed-fee design package covers measured survey, planning drawings, building regs and a tendered cost plan. Build cost is separate and quoted from drawings — never guessed from a phone call.
- What pushes a Mousehole extension over budget?
- Three things: ground conditions you didn't survey for, a planning condition that drives a material change, and "while we're at it" scope creep. We screen all three at feasibility stage so the number you start with is the number you finish on.
- 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 Mousehole specifically, we'd start by checking the Conservation Area boundary before committing to a direction.
- 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.
Mousehole is the hub for these neighbourhoods
We run extensions across Mousehole and the surrounding TR19 neighbourhoods — same studio, same site team.
- Lamorna
TR19
Other services in Mousehole
Nearby places we cover
Local neighbourhoods in Mousehole
If you're scoping an extension in Mousehole, the honest number depends on three things: ground conditions, finish level and how much of the existing fabric stays. We'll tell you which bracket you're in before you commit to a fee.