Mid Cornwall · TR3
Loft Conversions Threemilestone: TR3 planning, Mid Cornwall fabric
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. What works on a TR3 plot rarely works elsewhere — Threemilestone is the western residential and retail-park suburb of Truro, with the West Cornwall Hospital site nearby and significant new estate development on the Langarth Garden Village land, with a building stock that leans toward self-build plots in the Garden Village and modern Persimmon, Bellway and Wainhomes estates.
Threemilestone sits in Mid Cornwall — covering TR3 from Truro, Shortlanesend, Playing Place outward.
- ✓ 30+ years of Cornwall Council approvals
- ✓ Cornwall Council regulars across every sub-area
- ✓ Fixed-fee planning packages, no surprise invoices
- ✓ Measured-survey accuracy from day one
Local proof — Recent loft conversion enquiries from Threemilestone have clustered around self-build plots in the Garden Village — we know the route through Cornwall Council on these.
Get a free feasibility viewLocal context
Why Threemilestone is its own job.
Outside Conservation Area and AONB. Langarth Garden Village (3,500+ homes) is reshaping the west of Truro with strict design code expectations on adjacent sites. That sets the scene before any design work begins. For loft conversion specifically, Threemilestone sits outside the headline designations, which usually gives a slightly more flexible starting point — but parish-level character still matters. It's the kind of detail that decides whether a Threemilestone application gets approved at eight weeks or stalls in committee. The self-build plots in the Garden Village that dominate Threemilestone (and continue out toward Shortlanesend) set the tone for any loft conversion scheme here.
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 Threemilestone.
01
Stairs eat space — a loft conversion lives or dies by where the new staircase lands and what it costs you on the floor below.
02
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.
03
Cut-roof Cornish properties are easier to convert than modern trussed roofs; the structural strategy varies completely.
04
Cornish slate roofs come in a huge range of pitches — anything below a 30° pitch struggles to give usable headroom without raising the ridge.
Our process
How a Threemilestone 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
Why Threemilestone homeowners pick a local studio for loft conversion.
Building stock
Across Threemilestone (TR3) we work on 1970s and 1980s estates, modern Persimmon, Bellway and Wainhomes estates, self-build plots in the Garden Village, office and retail conversions. Each stock type drives a different loft conversion response — self-build plots in the Garden Village in particular needs careful detailing here.
Parish & policy
Threemilestone sits in the parish of Kenwyn, which matters for how parish-level consultation lands on a loft conversion application.
Coverage
We cover TR3 from our studio, with regular loft conversion jobs also running in Truro, Shortlanesend, Playing Place. Most Threemilestone site visits get booked within the same week.
How quickly can you visit a Threemilestone site?
Usually within the same week. Threemilestone (TR3) is on our regular Mid Cornwall run, alongside Truro, Shortlanesend, Playing Place. First visits are free and you'll get an honest feasibility view inside seven days.
Request a free visitFAQs
Threemilestone Loft Conversions — local questions answered.
- 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. In Threemilestone specifically, we'd start by checking the latest parish-level planning history before committing to a direction.
- 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.
- Will it add value?
- An extra bedroom and bathroom typically adds noticeably more value than the build cost in most Cornish markets — but the value matters less than the daily use you'll get from the space.
- How much does a loft conversion cost?
- A simple Velux conversion starts around £30,000 in Cornwall; a rear dormer with en-suite typically runs £45,000 to £65,000; hip-to-gable and mansards more. Stair location and bathroom complexity drive most of the cost.
- 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.
Threemilestone is part of Truro
Threemilestone sits inside the Truro catchment — we cover both as one loft conversion territory.
See Loft Conversions in Truro →Other services in Threemilestone
Nearby places we cover
Designing a loft conversion in Threemilestone is as much about reading the parish as reading the brief; we do both, and the planning outcomes follow.