South Cornwall · TR11
House Extensions in Mawnan
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. Reading Mawnan on the ground is half of the extension job — Mawnan is a rural parish in the TR11 area, with farmsteads, lanes and scattered homes defining its built character, with a building stock that leans toward farmhouses and rural cottages.
Mawnan sits in South Cornwall — covering TR11 from Mawnan Smith, Durgan, Truro outward.
- Cornwall AONB
- Rural / open-countryside policy area
- ✓ Measured-survey accuracy from day one
- ✓ One studio — design, planning and build under one roof
- ✓ Local to South Cornwall — not a national franchise
- ✓ Same team on paper as on site
Local watch-list
Common Mawnan pitfalls we plan around.
Watch #1
AONB landscape-impact scrutiny on visible elevations
Watch #2
Tighter Local Plan tests on isolated rural dwellings
Who this is for
Mawnan 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 Mawnan is its own job.
Open-countryside policy, access lanes, drainage and agricultural building history all need to be addressed before drawings go too far. For extension specifically, 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; 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 Mawnan job runs as a TR11-specific piece of work — local policy, local fabric, local builders. Most of our extension work in Mawnan lands on farmhouses, with detailing that has to nod to the wider Durgan 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 Mawnan.
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
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 Mawnan 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
Mawnan 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 Mawnan specifically, we'd start by checking AONB landscape sensitivity 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.
- 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.
- 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.
Mawnan is part of Mawnan Smith
Mawnan sits inside the Mawnan Smith catchment — we cover both as one extension territory.
See Extensions in Mawnan Smith →Local proof — Most Mawnan 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 Mawnan
Nearby places we cover
On a Mawnan site the success of a extension is decided in week one — by reading the constraints right, not by drawing them away.