West Cornwall · TR13 · Cornwall Council West
House extension costs in Helston — what TR13 homeowners actually pay
Most Helston cost questions land in the same bracket: a single-storey rear sits roughly £2,200–£2,800/m² built, a two-storey side runs £2,000–£2,500/m², and anything touching a stone-fronted elevation tends to add 8–12% for materials and detailing. We quote on measured drawings, not guesses. 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. What works on a TR13 plot rarely works elsewhere — Helston is the gateway to the Lizard Peninsula and Cornwall's most westerly market town, famous for the Furry Dance and a steep granite-paved Coinagehall Street, with a building stock that leans toward modern estates at Trannack and post-war semis.
Helston sits in West Cornwall — just off the A394; with Truro the closest city; covering TR13 from Porthleven, Mullion, Mawgan outward.
- Conservation Area
- ✓ Typical Helston single-storey rear: £55k–£85k build cost
- ✓ Two-storey side extension: £85k–£140k build cost
- ✓ Wrap-around / L-shaped: £110k–£180k build cost
- ✓ Design + planning + building regs fee from £4,800 (fixed)
Who this is for
In Helston 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.
Local watch-list
Local snags worth knowing before drawing a Helston extension.
Watch #1
Lizard AONB designation south of town
Watch #2
Granite-walled cottages with limited cavity options
Watch #3
Coinagehall Street Conservation Area frontage controls
Watch #4
RNAS Culdrose safeguarding zones on south-east approaches
Local proof — We typically have one or two extension jobs live in the TR13 area at any time, so the local planning officers know our drawings on sight.
Get a free feasibility viewFAQs
Helston Extensions — local questions answered.
- What's the average cost of a single-storey extension in Helston?
- For a typical 20–30m² rear extension in Helston (TR13) we'd expect £55k–£85k including VAT, depending on glazing spec and whether the kitchen is being reworked. Coastal exposure here pushes weather-tightness specs up, which is real money.
- Do extension costs in Helston include planning and building regs?
- Our fixed-fee design package covers measured survey, planning drawings, building regs and a tendered cost plan. Build cost is separate and quoted from drawings — never guessed from a phone call.
- What pushes a Helston extension over budget?
- Three things: ground conditions you didn't survey for, a planning condition that drives a material change, and "while we're at it" scope creep. We screen all three at feasibility stage so the number you start with is the number you finish on.
- 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. In Helston specifically, we'd start by checking the Conservation Area boundary before committing to a direction.
- 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.
Local context
Why Helston is its own job.
Cornwall Council's lens on Helston is consistent: the Conservation Area covers the medieval core and Coinagehall Street; shop frontages, sash windows and listed building stock dominate the design conversation. RNAS Culdrose to the south sets some height and roofline constraints in the southern parishes. For extension specifically, parts of Helston sit within a designated Conservation Area, which means materials, fenestration and roof pitches all need to read sympathetically with the existing streetscape. That's why we treat every Helston project as a TR13-area job first — not a generic Cornwall job with a postcode bolted on. The modern estates at Trannack that dominate Helston (and continue out toward Wendron) set the tone for any extension scheme here.
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.
Recent work nearby
Helston farm barn conversion last winter ran as a Class Q with full planning fallback.
See more recent West Cornwall work →What we focus on
Extensions considerations specific to Helston.
01
Cornish granite and slate-hung walls react differently to new openings than modern brickwork — lintel choice and structural sequencing matter.
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.
Our process
How a Helston 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.
Local fabric
Why Helston homeowners pick a local studio for extension.
Building stock
Across Helston (TR13) we work on Georgian townhouses, granite-and-slate terraces, Victorian villas, post-war semis, modern estates at Trannack. Each stock type drives a different extension response — modern estates at Trannack in particular needs careful detailing here.
Parish & policy
Helston is its own town in West Cornwall, with planning history that's specific to the TR13 catchment.
Coverage
We cover TR13 from our studio, with regular extension jobs also running in Porthleven, Mullion, Mawgan. Most Helston site visits get booked within the same week.
How quickly can you visit a Helston site?
Usually within the same week. Helston (TR13) is on our regular West Cornwall run, alongside Porthleven, Mullion, Mawgan. First visits are free and you'll get an honest feasibility view inside seven days.
Request a free visitHelston is the hub for these neighbourhoods
We run extensions across Helston and the surrounding TR13 neighbourhoods — same studio, same site team.
- Breage
TR13
- Ashton
TR13
- Sithney
TR13
- Nancegollan
TR13
- Godolphin Cross
TR13
- Wendron
TR13
- Porkellis
TR13
- Mawgan
TR12
- Trelowarren
TR12
Other services in Helston
Nearby places we cover
Local neighbourhoods in Helston
If you're scoping an extension in Helston, the honest number depends on three things: ground conditions, finish level and how much of the existing fabric stays. We'll tell you which bracket you're in before you commit to a fee.