East Cornwall · PL11 · Cornwall Council East
House Extensions in Downderry
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. A Downderry brief starts on the street, not the screen — Downderry is a holiday-coast settlement in the PL11 area, with strong second-home demand and exposed coastal building conditions, with a building stock that leans toward coastal bungalows and second homes.
Downderry sits in East Cornwall — just off the A38; covering PL11 from Looe, Duloe, Herodsfoot outward.
- Cornwall AONB
- Coastal exposure zone
- ✓Fixed-fee planning packages, no surprise invoices
- ✓Measured-survey accuracy from day one
- ✓One studio — design, planning and build under one roof
- ✓Local to East Cornwall — not a national franchise
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Local watch-list
Local snags worth knowing before drawing a Downderry extension.
Watch #1
AONB landscape-impact testing on anything read in long views across East Cornwall
Watch #2
Exposure detailing on coastal bungalows — fixings, render systems and joinery specified for salt-laden air
Watch #3
Trussed roofs and shallow foundations in the later PL11 estates, which change the structural strategy
Who this is for
In Downderry the extension brief is almost always a private homeowner improving a forever home — so we lead with feasibility and long-term value, not show-home rhetoric.
Page purpose
Drawings only, or drawings through to handover in Downderry?
Both routes are open on a PL11 project, and the honest answer depends on whether you already have a builder you trust. Plenty of Downderry clients take the drawings, tender them locally, then come back to us for the build if the numbers do not stack up.
- Route one: feasibility, planning and a tender-ready technical pack
- Route two: the same pack, then the build under one contract
- Either way the survey and feasibility work is identical, so the decision can wait
- Fees quoted per stage against the PL11 scope, not as one opaque figure
Keep reading
Other work we do around Downderry
Downderry is covered from our Looe run. Being a smaller place, the local detail matters more than the headline policy: lane access, neighbour proximity and what the immediate street already looks like.
Who this is for
What we can genuinely back up in Downderry
- Design and build are offered from the same studio, which means the person answering your Downderry questions has seen the detail built.
- Drawings, planning and building regulations are all produced in-house, so a extension enquiry does not get passed between firms.
- Designated-area work is routine here, so heritage and landscape statements are produced alongside the drawings rather than outsourced.
Planning rules change and every site is different. For the final position on your address, check with Cornwall Council as the local planning authority or the Planning Portal.
Scope
The parts of the job we can take on in Downderry
These stages can be bought separately. Most PL11 projects use three of them.
Heritage and design statements
Written justification where designation makes the design case as important as the drawing.
Structural coordination
Calculations coordinated with the drawings so building control sees one consistent story.
Full design and build
One contract from first sketch to handover, with the same team on paper and on site.
Construction and technical drawings
1:10 and 1:20 details for the parts of the job builders normally have to guess at.
Building regulation drawings
Full Plans sets with sections, construction notes and coordinated structural information.
Local context
Why Downderry is its own job.
Planning scrutiny often focuses on visual impact, occupancy, parking, overlooking and whether replacement buildings respect the coastal edge. 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; coastal salt-laden air around Downderry drives detailing choices — fixings, render systems and timber treatments all need to be specified for exposure. So every Downderry job runs as a PL11-specific piece of work — local policy, local fabric, local builders. Most of our extension work in Downderry lands on coastal bungalows, with detailing that has to nod to the wider Duloe 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 Downderry.
01
Drainage on older Cornish properties is rarely on a clean modern map; CCTV survey before design is often money well spent.
02
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.
03
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.
Quick check
Want a straight answer on whether your Downderry project is worth pursuing?
Send a few details — we'll come back within 1 working day with a plain-English view on planning risk, likely cost band and whether it's a project we'd take on.
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Get a free feasibility view
For projects in Downderry and the PL11 area.
Our process
How a Downderry 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
Downderry Extensions — local questions answered.
- 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 Downderry specifically, we'd start by checking AONB landscape sensitivity before committing to a direction.
- We live in the house. Can a extension in Downderry be done while we stay put?
- Usually yes for single-storey and rear work, with a temporary kitchen or bathroom arrangement agreed before the start. Whole-house remodels and roof work in Downderry are often easier if you move out for a few weeks. We set that expectation at feasibility stage rather than halfway through.
- 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.
- 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.
- 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.
Downderry is part of Looe
Downderry sits inside the Looe catchment — we cover both as one extension territory.
See Extensions in Looe →Local proof — We typically have one or two extension jobs live in the PL11 area at any time, so the local planning officers know our drawings on sight.
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Nearby places we cover
Designing a extension in Downderry is as much about reading the parish as reading the brief; we do both, and the planning outcomes follow. Applications are dealt with through Cornwall Council, with Liskeard the office we deal with most for PL11.
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