West Cornwall · TR26 · Cornwall Council West
Granny annexes in St Ives — self-contained living, done well
A granny annexe in St Ives is either an attached extension with a separate entrance, a garden building with independent services, or a garage conversion. Cornwall Council treats all three under the "ancillary residential" test — meaning they must remain connected to the main dwelling's planning use. Get the planning wording right and the design opens up. 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 St Ives, that work is shaped by the place itself — St Ives is a designated Area of Outstanding Natural Beauty town with a tightly packed historic harbour, the Tate gallery and some of the steepest streets in Cornwall, with a building stock that leans toward Edwardian guesthouses and granite terraces.
St Ives sits in West Cornwall — just off the A3074; with Truro the closest city; 1 miles from Carbis Bay, 3 miles from Hayle.
- Conservation Area
- Cornwall AONB
- Coastal exposure zone
- ✓ Attached annexe: £75k–£110k built
- ✓ Detached garden annexe: £95k–£140k
- ✓ Ancillary use planning included
- ✓ Self-contained services throughout
Local proof — Recent extension enquiries from St Ives have clustered around Edwardian guesthouses — we know the route through Cornwall Council on these.
Get a free feasibility viewLocal context
Why St Ives is its own job.
Locally, st Ives operates a Neighbourhood Plan with a principal residence policy on most new dwellings — second homes and holiday lets face strong policy resistance. The Conservation Area covers Downalong, the harbour and most of the town centre, where granite, slate and lime-render detailing is non-negotiable. For extension specifically, parts of St Ives 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 St Ives drives detailing choices — fixings, render systems and timber treatments all need to be specified for exposure. Which is why we scope St Ives projects parish-up, not template-down — the TR26 context shapes the design from day one. Whether the project is on Edwardian guesthouses in the centre or further out toward Hayle, 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 St Ives.
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
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.
04
Wind and sea-spray exposure can drive material choices on west-facing extensions; we detail accordingly.
Our process
How a St Ives 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 West Cornwall studio is the right fit for St Ives extension.
Building stock
Across St Ives (TR26) we work on fishermen's cottages, granite terraces, Victorian villas, Edwardian guesthouses, modern hillside homes above the town. Each stock type drives a different extension response — Edwardian guesthouses in particular needs careful detailing here.
Parish & policy
St Ives sits in the parish of St Ives, which matters for how parish-level consultation lands on a extension application.
Coverage
We cover TR26 from our studio, with regular extension jobs also running in Carbis Bay, Hayle, Lelant. Most St Ives site visits get booked within the same week.
What does a first St Ives consultation cost?
Nothing. We come to the property, walk the site, talk through what works on a TR26 plot and follow up with a written feasibility note inside a week — no obligation either way.
Request a free visitRecent work nearby
Carbis Bay clifftop rebuild we ran last year leaned on a granite plinth + standing-seam zinc roof.
See more recent West Cornwall work →FAQs
St Ives Extensions — local questions answered.
- Do I need planning permission for a granny annexe in St Ives?
- Yes — annexes always need planning consent to establish ancillary residential use. Attached annexes go through householder; detached garden annexes need full planning.
- How much does a granny annexe cost in St Ives?
- £75k–£140k for a 30–55m² annexe with kitchenette, bedroom, bathroom and living area. Detached garden annexes cost 10–20% more than attached (utility runs and separate roof).
- Can we let out the annexe as a holiday let later?
- Only with a further change-of-use application. Ancillary consent explicitly ties the annexe to the main dwelling — subletting breaches that condition.
- 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 St Ives specifically, we'd start by checking the Conservation Area boundary before committing to a direction.
- 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.
St Ives is the hub for these neighbourhoods
We run extensions across St Ives and the surrounding TR26 neighbourhoods — same studio, same site team.
- Carbis Bay
TR26
- Nancledra
TR20
Other services in St Ives
Nearby places we cover
Local neighbourhoods in St Ives
A St Ives granny annexe is 50% design, 50% planning wording — get the ancillary-use case right and everything downstream is straightforward.
Design a granny annexe on your St Ives plot
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