Most barn conversions in Cornwall and Devon require full planning permission from the local authority, with the process taking 6 to 18 months from application to move-in and costing between £800 and £1,500 per square metre for construction. Here is everything you need to know to plan your barn conversion successfully.
The first step in any barn conversion project is establishing your planning route. In Cornwall and Devon, there are two main options:
Required for most barn conversions, particularly those involving significant external alterations, extensions, or barns within conservation areas and the Cornwall AONB. You will need to submit a full application to Cornwall Council or your relevant Devon district council (Exeter, East Devon, North Devon, Torridge, or West Devon). The standard determination period is 8 weeks, though complex applications often take 13 weeks or longer.
Some agricultural barns qualify for conversion under Class Q permitted development rights, which require only a “prior approval” application rather than full planning permission. This is faster and cheaper, but the criteria are strict:
Note that Cornwall Council applies Class Q cautiously, particularly in the AONB and World Heritage Site areas. We recommend a pre-application enquiry (£50-£150) before committing to this route.
If your barn is listed (Grade I, II*, or II), you will need listed building consent in addition to planning permission. This applies to any works affecting the building's character, including internal alterations. The process takes longer—typically 13 weeks minimum—and requires a heritage impact assessment. Cornwall has a significant number of listed agricultural buildings, particularly in its mining heritage areas.
A well-managed barn conversion follows a clear sequence. Skipping stages leads to costly mistakes, delays, and potential enforcement action.
Budget realistically. Barn conversions cost more per square metre than new builds because you are working within existing constraints. Here is what to expect in 2026:
On top of the build cost, allow for:
The best barn conversions respect the building's agricultural character while creating comfortable modern living spaces. At RPG Carpentry & Joinery, we specialise in using traditional materials and techniques:
With over 10 years of experience in barn renovation carpentry across Cornwall and Devon, we understand how to work with these buildings sensitively. From structural oak framing to bespoke staircases, oak flooring, and fitted furniture, we handle all carpentry and joinery elements of your conversion.
Cornwall is a unitary authority, so all planning applications go through Cornwall Council's planning portal. The county has extensive AONB coverage, World Heritage Site areas (mining heritage), and numerous conservation areas. Pre-application advice is available and strongly recommended for barn conversions.
Devon has multiple district councils, each with slightly different local plan policies on barn conversions. South Hams and West Devon have particularly strict policies in the Dartmoor and South Devon AONB areas. North Devon and Torridge tend to be more supportive of agricultural building conversions that contribute to rural housing supply.
Planning a barn conversion?
RPG Carpentry & Joinery provides expert carpentry and structural joinery for barn conversions across Cornwall and Devon. Call 07717 299 777 or get in touch to discuss your project.
In most cases, yes. Full planning permission is required to convert an agricultural barn into a dwelling in Cornwall. However, some agricultural buildings may qualify for Class Q permitted development rights, which allow conversion without full planning permission, subject to prior approval from Cornwall Council. Class Q has strict criteria including the building being structurally sound, under 865m², and in agricultural use since before March 2013. Always check with Cornwall Council's planning department before proceeding.
A typical barn conversion in Cornwall or Devon takes 6 to 18 months from initial planning application to completion. The planning stage alone takes 8-13 weeks for a standard application, longer for listed buildings. Construction typically takes 4-12 months depending on the barn's size, condition, and the complexity of the conversion. Budget an additional 2-3 months for surveys, structural engineer reports, and building regulations approval before construction begins.
Class Q is a permitted development right that allows the change of use of agricultural buildings to residential dwellings without full planning permission. Instead, you apply for “prior approval” from the local authority, which is faster and cheaper. The building must have been used for agriculture on or before 20 March 2013, must be structurally capable of conversion without major rebuilding, and must not exceed 865m² of cumulative floor space. The local authority can only refuse on limited grounds including transport, contamination, flooding, and design.
Barn conversions in Cornwall and Devon typically cost between £800 and £1,500 per square metre for the construction phase, excluding land purchase and professional fees. A basic conversion of a structurally sound barn starts around £800/m², while a high-specification finish with oak framing, bespoke joinery, and premium materials reaches £1,200-£1,500/m². Listed barns or those requiring significant structural intervention can exceed £1,500/m². Professional fees typically add 10-15% to the overall build cost.