West Cornwall · TR13 · Cornwall Council West
Extensions for Trewennack (TR13)
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 way we approach extension in Trewennack starts with a measured walk-round — Trewennack is a small rural hamlet in the TR13 area, with scattered homes, lanes and a deliberately quiet settlement pattern, with a building stock that leans toward converted barns and small infill homes.
Trewennack sits in West Cornwall — just off the A30; covering TR13 from Helston, Breage, Ashton outward.
- Rural / open-countryside policy area
- ✓Fixed-fee planning packages, no surprise invoices
- ✓Measured-survey accuracy from day one
- ✓Same team on paper as on site
- ✓Plain-English feasibility before any drawings
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Free Trewennack feasibility call
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Page purpose
Drawings only, or drawings through to handover in Trewennack?
Both routes are open on a TR13 project, and the honest answer depends on whether you already have a builder you trust. Plenty of Trewennack 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 TR13 scope, not as one opaque figure
Scope
Scope options for Trewennack clients
Clients in Trewennack take different slices of this list, and that is deliberate.
Measured survey
An accurate record of what is actually there, which is where most avoidable cost is removed.
Full design and build
One contract from first sketch to handover, with the same team on paper and on site.
Building regulation drawings
Full Plans sets with sections, construction notes and coordinated structural information.
Planning application drawings
Existing and proposed plans, elevations, site and block plans drawn to validation standard.
Construction and technical drawings
1:10 and 1:20 details for the parts of the job builders normally have to guess at.
Local watch-list
The TR13 constraints that shape a extension brief.
Watch #1
Local Plan tests on isolated dwellings, plus lane access for plant and deliveries around Trewennack
Watch #2
Party Wall notices and shallow roof voids typical of cottages in the TR13 district
Who this is for
Straight facts about working with us here
- Design and build are offered from the same studio, which means the person answering your Trewennack questions has seen the detail built.
- Applications for Trewennack are handled through Cornwall Council, with Truro the nearest planning office we deal with regularly.
- Drawings, planning and building regulations are all produced in-house, so a extension enquiry does not get passed between firms.
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.
What we focus on
Extensions considerations specific to Trewennack.
01
Wind and sea-spray exposure can drive material choices on west-facing extensions; we detail accordingly.
02
Drainage on older Cornish properties is rarely on a clean modern map; CCTV survey before design is often money well spent.
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.
Quick check
Want a straight answer on whether your Trewennack 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 Trewennack and the TR13 area.
Local context
Why Trewennack is its own job.
In Trewennack the planning picture is specific: the main planning test is usually whether the proposal remains subordinate, locally detailed and acceptable on access, drainage and neighbour amenity. For extension specifically, 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. That local reading is what makes a Trewennack (TR13) project different from a generic Cornwall scheme — and is the whole reason we work this way. On converted barns in particular — the kind you'll also find toward Sithney — 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.
Our process
How a Trewennack 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
Trewennack 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 Trewennack specifically, we'd start by checking the latest parish-level planning history 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.
- We live in the house. Can a extension in Trewennack 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 Trewennack are often easier if you move out for a few weeks. We set that expectation at feasibility stage rather than halfway through.
- 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.
Trewennack is part of Helston
Trewennack sits inside the Helston catchment — we cover both as one extension territory.
See Extensions in Helston →Keep reading
Where to go next from Trewennack
Trewennack is covered from our Helston 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.
Other services in Trewennack
Nearby places we cover
For Trewennack homeowners weighing up a extension, the right starting point is honest feasibility — that's what we lead with, before any drawings. farmhouses in particular need a tailored structural answer.
Ready to discuss your project in Trewennack? We are on the A30 regularly.
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