East Cornwall · PL22
Granny annexes in Lostwithiel — self-contained living, done well
A granny annexe in Lostwithiel 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. Working in Lostwithiel means starting from the PL22 context — Lostwithiel is a medieval town on the river Fowey, formerly the capital of Cornwall, with a strong antiques trade, a Norman church and an extensive Conservation Area, with a building stock that leans toward Victorian terraces and post-war estates.
Lostwithiel sits in East Cornwall — covering PL22 from Fowey, Lerryn outward.
- Conservation Area
- ✓ Attached annexe: £75k–£110k built
- ✓ Detached garden annexe: £95k–£140k
- ✓ Ancillary use planning included
- ✓ Self-contained services throughout
Local watch-list
The PL22 constraints that shape a extension brief.
Watch #1
Conservation Area material and fenestration controls in central Lostwithiel
Who this is for
Lostwithiel 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 Lostwithiel is its own job.
In Lostwithiel the planning picture is specific: conservation Area is extensive, covering the medieval streets, the church and the riverside. Listed buildings are very common; flood zone designation affects properties near the river. For extension specifically, parts of Lostwithiel sit within a designated Conservation Area, which means materials, fenestration and roof pitches all need to read sympathetically with the existing streetscape. That local reading is what makes a Lostwithiel (PL22) project different from a generic Cornwall scheme — and is the whole reason we work this way. On Victorian terraces in particular — the kind you'll also find toward Tywardreath — the extension brief always has to read the existing fabric first.
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 Lostwithiel.
01
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.
02
Cornish granite and slate-hung walls react differently to new openings than modern brickwork — lintel choice and structural sequencing matter.
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 Lostwithiel 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
Lostwithiel Extensions — local questions answered.
- Do I need planning permission for a granny annexe in Lostwithiel?
- 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 Lostwithiel?
- £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.
- 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 Lostwithiel specifically, we'd start by checking the Conservation Area boundary 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.
- 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.
Lostwithiel is the hub for these neighbourhoods
We run extensions across Lostwithiel and the surrounding PL22 neighbourhoods — same studio, same site team.
- Lerryn
PL22
- St Winnow
PL22
- Lanlivery
PL30
- Sweetshouse
PL24
- Redmoor
PL30
Local proof — Recent extension enquiries from Lostwithiel have clustered around Victorian terraces — we know the route through Cornwall Council on these.
Get a free feasibility viewOther services in Lostwithiel
Nearby places we cover
Local neighbourhoods in Lostwithiel
A Lostwithiel granny annexe is 50% design, 50% planning wording — get the ancillary-use case right and everything downstream is straightforward.
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