Mid Cornwall · TR3
Loft Conversions in Threemilestone
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. In Threemilestone, that work is shaped by the place itself — 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 1970s and 1980s estates and modern Persimmon, Bellway and Wainhomes estates.
Local 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. 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. That's why we treat every Threemilestone project as a TR3-area job first — not a generic Cornwall job with a postcode bolted on.
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
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.
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.
FAQs
Threemilestone Loft Conversions — common questions.
- 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.
Other services in Threemilestone
Nearby places we cover