South Cornwall · PL22
House Extensions in Lerryn
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. The Lerryn version of this work has its own character — Lerryn is a creekside settlement in the PL22 area, with waterside homes, wooded valleys and narrow-lane access shaping the brief, with a building stock that leans toward boat sheds and waterside homes.
Lerryn sits in South Cornwall — covering PL22 from Lostwithiel, St Winnow, Lanlivery outward.
- Conservation Area
- ✓ One studio — design, planning and build under one roof
- ✓ Local to South Cornwall — not a national franchise
- ✓ Same team on paper as on site
- ✓ Fixed-fee planning packages, no surprise invoices
Local watch-list
The PL22 constraints that shape a extension brief.
Watch #1
Conservation Area material and fenestration controls in central Lerryn
Who this is for
Lerryn 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 Lerryn is its own job.
Creekside ecology, flood risk, trees and views across the water often matter as much as the building form itself. For extension specifically, parts of Lerryn sit within a designated Conservation Area, which means materials, fenestration and roof pitches all need to read sympathetically with the existing streetscape. So every Lerryn job runs as a PL22-specific piece of work — local policy, local fabric, local builders. Most of our extension work in Lerryn lands on boat sheds, with detailing that has to nod to the wider St Winnow 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 Lerryn.
01
Cornish granite and slate-hung walls react differently to new openings than modern brickwork — lintel choice and structural sequencing matter.
02
Wind and sea-spray exposure can drive material choices on west-facing extensions; we detail accordingly.
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
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.
Our process
How a Lerryn 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
Lerryn Extensions — local questions answered.
- 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. In Lerryn 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.
- 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.
- 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.
Lerryn is part of Lostwithiel
Lerryn sits inside the Lostwithiel catchment — we cover both as one extension territory.
See Extensions in Lostwithiel →Local proof — Recent extension enquiries from Lerryn have clustered around boat sheds — we know the route through Cornwall Council on these.
Get a free feasibility viewOther services in Lerryn
Nearby places we cover
If you're considering a extension project in the PL22 area, our deep understanding of Lerryn's architectural character can help navigate the process smoothly.