Lizard Peninsula · TR12 · Cornwall Council West
Dormer loft conversion costs in Mullion — TR12 numbers that stack up
A rear dormer in Mullion typically runs £45k–£65k for a single bedroom and en-suite; a full-width or L-shape rises to £55k–£85k. On the granite cottages around the church stock we see most often here, the biggest cost variable is the existing rafter spacing — the wider it is, the more steel goes in. A well-designed loft conversion adds a bedroom, an en-suite and useful storage to homes that were never built with the upper floor in mind — usually inside permitted development and almost always cheaper per square metre than extending sideways. On a Mullion site, the brief always meets the place — Mullion is the largest village on the Lizard Peninsula, AONB-designated, with a fifteenth-century church, a working cove and the highest concentration of period housing on the peninsula, with a building stock that leans toward granite cottages around the church and modern AONB-sensitive replacement dwellings.
Mullion sits in Lizard Peninsula — just off the A394; covering TR12 from Mawgan, Ruan Minor, The Lizard outward.
- Conservation Area
- Cornwall AONB
- Coastal exposure zone
- Rural / open-countryside policy area
- ✓Rear dormer: £45k–£65k built
- ✓Full-width dormer: £55k–£85k
- ✓L-shape dormer: £65k–£95k
- ✓On-site programme: 10–14 weeks
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Free Mullion feasibility call
Tell us about your loft conversion. We reply within 1 working day — no obligation.
Who this is for
In Mullion the loft conversion 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
The TR12 constraints that shape a loft conversion brief.
Watch #1
Conservation Area controls on materials, window proportions and roof form through central Mullion
Watch #2
AONB landscape-impact testing on anything read in long views across Lizard Peninsula
Watch #3
Exposure detailing on granite cottages around the church — fixings, render systems and joinery specified for salt-laden air
Watch #4
Local Plan tests on isolated dwellings, plus lane access for plant and deliveries around Mullion
Local proof — Our Lizard Peninsula workload means a Mullion loft conversion project never has to wait for an out-of-county team to drive down.
Get a free feasibility viewFAQs
Mullion Loft Conversions — local questions answered.
- How much does a rear dormer cost in Mullion?
- £45k–£65k for a standard rear dormer including new stair, one en-suite and Velux on the front slope. Timber-clad dormers add ~£3k, tile-hung dormers add ~£5k.
- Are dormer lofts permitted development in Mullion?
- No — Conservation Area removes dormer PD rights, full planning needed.
- What's the on-site build time for a dormer loft?
- 10–14 weeks including steels, weather-tight enclosure, first fix and finishes. We keep the property occupied throughout on most jobs.
- Will I have enough headroom?
- We need a minimum 2.2 metres ridge-to-joist before alterations to make a usable conversion straightforward. Less than that and we'd consider raising the ridge, which is a planning conversation, not a permitted development one. In Mullion specifically, we'd start by checking the Conservation Area boundary before committing to a direction.
- Can I live downstairs while it's built?
- Yes — most loft conversions are built with the family staying in the house. There'll be a couple of disruptive days when the staircase comes through, but the bulk of the work is upstairs.
- Do I need planning permission for a loft conversion?
- Often no — most loft conversions sit inside permitted development on a typical Cornish house. Conservation Areas, AONB and properties on principal elevations need full planning, and we'll confirm at first review.
Quick check
Want a straight answer on whether your Mullion 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 Mullion and the TR12 area.
Who this is for
Why this page exists, and who it is for
- Drawings, planning and building regulations are all produced in-house, so a loft conversion 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.
- Applications for Mullion 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.
Keep reading
Follow the chain: survey, drawings, build
We cover Mullion and the wider TR12 district directly. Loft Conversions enquiries here are common enough that we know the constraints before the first visit.
Page purpose
Drawings only, or drawings through to handover in Mullion?
Both routes are open on a TR12 project, and the honest answer depends on whether you already have a builder you trust. Plenty of Mullion 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 TR12 scope, not as one opaque figure
Scope
What we can draw, survey and build around Mullion
These stages can be bought separately. Most TR12 projects use three of them.
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.
Local context
Why Mullion is its own job.
Locally, mullion Conservation Area covers the village centre; the wider parish is entirely within the AONB and includes Heritage Coast designation. Cliff-edge and coastal margin sites face the strictest controls in West Cornwall. For loft conversion specifically, parts of Mullion 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 Mullion drives detailing choices — fixings, render systems and timber treatments all need to be specified for exposure; 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. Which is why we scope Mullion projects parish-up, not template-down — the TR12 context shapes the design from day one. Whether the project is on granite cottages around the church in the centre or further out toward Cury, the loft conversion response is locally tuned. Historic fabric changes the sequence: survey first, then design around what the building can take. Consent routes for listed buildings sit separately from ordinary planning, so treat any general guidance here as a starting point and check with Cornwall Council. Exposure is the real design driver near the water: wind-driven rain, salt and driving damp push detailing towards better weathering, sheltered openings and robust fixings. Where an AONB or coastal policy applies, visual impact usually carries more weight than size.
Planning note
Most Cornish loft conversions are permitted development — but a Certificate of Lawfulness is worth the extra week and small fee for resale protection.
What we focus on
Loft Conversions considerations specific to Mullion.
01
Cut-roof Cornish properties are easier to convert than modern trussed roofs; the structural strategy varies completely.
02
Building regs require minimum 2.0 metre headroom over the stairs and 30-minute fire protection on the existing stair enclosure — both shape the design.
03
Permitted development volume allowances are 40 cubic metres on a terrace and 50 on a detached or semi — but rear dormers in Conservation Areas often need full planning.
04
Stairs eat space — a loft conversion lives or dies by where the new staircase lands and what it costs you on the floor below.
Our process
How a Mullion loft conversion project runs.
Step 1
Feasibility
Roof, headroom, stair landing and structural assessment.
Step 2
Design
Layout options that respect the staircase, headroom and bathroom positioning.
Step 3
Approvals
Planning or permitted development confirmation, plus building regs.
Step 4
Build
Sequenced to keep the family living downstairs throughout most of the work.
Step 5
Handover
Finish, snag, certify, hand over the keys.
Loft conversions typically run six to eighteen weeks on site depending on type, with four to eight weeks of design and approvals beforehand.
Local fabric
Choosing a loft conversion team that actually knows TR12.
Building stock
Across Mullion (TR12) we work on granite cottages around the church, Edwardian guesthouses, 1960s coastal bungalows, modern AONB-sensitive replacement dwellings. Each stock type drives a different loft conversion response — granite cottages around the church in particular needs careful detailing here.
Parish & policy
Mullion is its own town in Lizard Peninsula, with planning history that's specific to the TR12 catchment.
Coverage
We cover TR12 from our studio, with regular loft conversion jobs also running in Helston. Most Mullion site visits get booked within the same week.
What does a first Mullion consultation cost?
Nothing. We come to the property, walk the site, talk through what works on a TR12 plot and follow up with a written feasibility note inside a week — no obligation either way.
Request a free visitOther services in Mullion
Nearby places we cover
Dormer costs in Mullion track ceiling height and steel — not floor area. A quick attic measure at first visit sets the bracket you're actually in.
Cost a dormer loft on your Mullion home
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