West Cornwall · TR17 · Cornwall Council West
Single storey extension costs in Marazion, and what actually moves the number
A single storey rear or side extension is the most common brief we take in Marazion, and the cost gap between two apparently identical projects usually comes down to four things: how the ground behaves once it is opened up, how much glazing is in the rear elevation, whether the kitchen is being reworked at the same time, and how exposed the elevation is to weather coming off the sea, which drives the weather-tightness detailing. 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. Anchor any Marazion extension in the local fabric and the rest follows — Marazion sits opposite St Michael's Mount across a tidal causeway and is one of Cornwall's oldest chartered towns, designated AONB for its setting, with a building stock that leans toward Georgian seafront houses and Victorian villas.
Marazion sits in West Cornwall — just off the A30; with Truro the closest city; 3 miles from Penzance.
- Conservation Area
- Cornwall AONB
- Coastal exposure zone
- ✓Cost banded feasibility before any design fee is committed
- ✓Marazion ground and access assessed on the first visit
- ✓Drawings and build from one studio, so the detail is priced not guessed
- ✓Free first consultation across West Cornwall
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Free Marazion feasibility call
Tell us about your extension. We reply within 1 working day — no obligation.
Who this is for
In Marazion 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
Common Marazion pitfalls we plan around.
Watch #1
St Michael's Mount setting controls across south-facing plots
Watch #2
Conservation Area on the historic core
Watch #3
Tidal flood zone along the seafront
Watch #4
AONB-level landscape impact on rising ground behind town
Local proof — Our West Cornwall workload means a Marazion extension project never has to wait for an out-of-county team to drive down.
Get a free feasibility viewFAQs
Marazion Extensions — local questions answered.
- What drives the cost of a single storey extension in Marazion?
- Ground conditions, glazing area, structural openings into the existing house, drainage runs and access for materials. In Marazion (TR17) access is often the quiet one, because a site a lorry cannot reach is a site where everything is handled twice.
- Is a rate per square metre reliable?
- Only as a sanity check. Two extensions of the same size can differ by a third once you change the glazing spec, the roof form and the amount of existing structure being altered. We price from drawings, not from a rate.
- Does using one studio for drawings and build change the cost?
- It changes where the cost is certain. Because we draw the scheme and then build it, the detail that a separate builder would price as a risk is already resolved on paper, so there is less contingency priced into the unknowns.
- What is the cheapest way to add space in Marazion?
- Usually reworking what already exists before extending: a garage conversion, a rethought internal layout, or a smaller extension that unlocks a better plan. We will say so if that is the better answer for your house, even though it is a smaller job for us.
- 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. In Marazion specifically, we'd start by checking the Conservation Area boundary before committing to a direction.
- 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.
Quick check
Want a straight answer on whether your Marazion 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 Marazion and the TR17 area.
Scope
What we can draw, survey and build around Marazion
Clients in Marazion take different slices of this list, and that is deliberate.
Full design and build
One contract from first sketch to handover, with the same team on paper and on site.
Measured survey
An accurate record of what is actually there, which is where most avoidable cost is removed.
Construction and technical drawings
1:10 and 1:20 details for the parts of the job builders normally have to guess at.
Heritage and design statements
Written justification where designation makes the design case as important as the drawing.
Building regulation drawings
Full Plans sets with sections, construction notes and coordinated structural information.
Page purpose
Drawings only, or drawings through to handover in Marazion?
Both routes are open on a TR17 project, and the honest answer depends on whether you already have a builder you trust. Plenty of Marazion 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 TR17 scope, not as one opaque figure
Keep reading
Follow the chain: survey, drawings, build
We cover Marazion and the wider TR17 district directly, typically alongside jobs in Penzance. Extensions enquiries here are common enough that we know the constraints before the first visit.
Who this is for
Why this page exists, and who it is for
- Designated-area work is routine here, so heritage and landscape statements are produced alongside the drawings rather than outsourced.
- Sites we know on the ground here include the area around the causeway and St Michael's Mount.
- Design and build are offered from the same studio, which means the person answering your Marazion questions has seen the detail built.
- Applications for Marazion are handled through Cornwall Council, with Truro the nearest planning office we deal with regularly.
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.
Local context
Why Marazion is its own job.
The planning backdrop in West Cornwall is real, not abstract: the whole town centre is within the Conservation Area and the AONB; views to and from St Michael's Mount are a material planning consideration on most schemes. Roof pitches, ridge heights and seaward elevations are tightly controlled. For extension specifically, parts of Marazion sit within a designated Conservation Area, which means materials, fenestration and roof pitches all need to read sympathetically with the existing streetscape; 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 Marazion drives detailing choices — fixings, render systems and timber treatments all need to be specified for exposure. Treat the TR17 parish brief as the design brief and the Marazion application has somewhere to land. Whether the project is on Georgian seafront houses in the centre or further out toward Goldsithney, the extension response is locally tuned. On older stock, the practical constraint is usually joinery, render and roof line rather than the extension itself. We draw those details out early so an extension submission is not sent back for missing information. Confirm listing status with the local planning authority before assuming permitted development. Salt air and prevailing wind change specification long before they change planning. We tend to draw weathering details in full, then check whether coastal or AONB policy narrows the design options for this address.
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
Behind-the-Square cottage we extended last winter used a slim glazed link to keep the original roof intact.
See more recent West Cornwall work →What we focus on
Extensions considerations specific to Marazion.
01
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.
02
Wind and sea-spray exposure can drive material choices on west-facing extensions; we detail accordingly.
03
Drainage on older Cornish properties is rarely on a clean modern map; CCTV survey before design is often money well spent.
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 Marazion 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
Choosing an extension team that actually knows TR17.
Building stock
Across Marazion (TR17) we work on granite cottages, Georgian seafront houses, Victorian villas, 1960s bungalows on Green Lane, modern coastal builds. Each stock type drives a different extension response — Georgian seafront houses in particular needs careful detailing here.
Parish & policy
Marazion is its own town in West Cornwall, with planning history that's specific to the TR17 catchment.
Coverage
We cover TR17 from our studio, with regular extension jobs also running in Penzance. Most Marazion site visits get booked within the same week.
What does a first Marazion consultation cost?
Nothing. We come to the property, walk the site, talk through what works on a TR17 plot and follow up with a written feasibility note inside a week — no obligation either way.
Request a free visitOther services in Marazion
Nearby places we cover
The honest answer for Marazion is that a rate per square metre is a starting point, not a price. We give you a cost band at feasibility stage, then a real figure once the drawings exist and the work can be priced properly.
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