Home Extension Costs in Devon
A clear, no-jargon guide to what you can expect to pay for a home extension across Exeter, Honiton, Sidmouth, Exmouth and the wider Devon area in 2026 \u2014 and the key factors that move the final price.
What affects the cost of an extension?
Several factors influence the price of a home extension in Devon. The size of the build is the most obvious \u2014 a larger footprint means more materials, more labour and more time. But specification matters just as much: a simple utility room with basic finishes costs far less per square metre than a bespoke oak-framed kitchen-diner with bi-fold doors, a roof lantern and underfloor heating.
Ground conditions, access to the site, and whether your property sits in a conservation area all play a part too. Older Devon properties \u2014 stone-built cottages, period terraces and 1960s bungalows \u2014 can throw up surprises once walls are opened, so a realistic contingency is essential.
Location within Devon also has an effect. Extension costs in Exeter and popular coastal towns like Sidmouth and Exmouth tend to run slightly higher than in inland areas, reflecting demand and labour availability across the region.
Typical Extension Costs in Devon
Ballpark ranges based on projects we have delivered across Devon. Your final quote depends on size, specification and site conditions.
Prices are estimates for guidance only. Contact RC-Builders Ltd for a free, itemised quote tailored to your project.
Additional costs to budget for
Beyond the build itself, allow for the professional fees and approvals that keep your extension legal and structurally sound. Many homeowners also set aside a contingency for the unexpected \u2014 particularly in older Devon properties where damp, subsidence or outdated wiring can surface once work begins.
- Planning application fees (where full permission is required)
- Building regulations approval and inspections
- Structural engineer calculations and fees
- Party wall agreements with neighbouring properties
- VAT on the full build cost
- A 10–15% contingency for unforeseen issues
How to keep costs under control
The most effective way to manage your budget is to fix the design before construction starts. Changes mid-build are the single biggest cause of cost overruns. A fixed-price contract from a family-run builder like RC-Builders Ltd gives you certainty from day one.
- Fix the design before construction starts — mid-build changes are the biggest cause of overspends
- Choose standard window sizes rather than bespoke glazing
- Keep new plumbing and electrics close to existing service runs
- Avoid structural steel where an alternative span is possible
- Use a fixed-price contract so you know the total from day one