Two-storey extensions in St Austell
Everything for a two-storey extension in St Austell, in one place: types, guide prices for South West England, the approval rules in England and how to get started.
St Austell at a glance
- Postcode districts
- PL23, PL24, PL25 and PL26
- Area
- Cornwall, England
- Price region
- South West England
- Nearest towns
- Bodmin (9.2 miles), Truro (13.5 miles), Newquay (14.1 miles), Falmouth (18.5 miles)
- Distance to Truro
- about 13.5 miles
- Approvals
- Two-storey rear: up to 3 m deep and 7 m from the rear boundary under permitted development. Side, wraparound and front: planning permission.
We cover St Austell (PL23, PL24, PL25 and PL26) and the places around it, including Bodmin (9.2 miles), Truro (13.5 miles) and Newquay.
Extensions available in St Austell
Two-storey rear extensions
Design, approvals and build for St Austell homes. Guide from £57,500.
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Two-storey side extensions
Guide from £88,500 in St Austell, including VAT.
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Two-storey wraparound extensions
Design, approvals and build for St Austell homes. Guide from £124,000.
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Part single, part two-storey extensions
St Austell guide price from £74,000, Standard spec.
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Extensions over a garage
St Austell guide price from £32,500, Standard spec.
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First-floor extensions
For homes in St Austell: typical guide from £26,000.
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Two-storey extensions for semi-detached houses
St Austell guide price from £57,500, Standard spec.
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Two-storey extensions for detached houses
From £88,500 in St Austell. Free visit to firm it up.
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Kitchen extensions with bedrooms above
From £57,500 (before kitchen units) in St Austell. Free visit to firm it up.
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Extra bedroom and en-suite extensions
Guide from £57,500 (plus en-suite) in St Austell, including VAT.
Learn moreWhich type suits your house?
Rear and side extensions suit most semi-detached and detached houses with room around them. Terraced and town-centre homes can take a two-storey extension too, with more care over neighbours, light and access.
Also available in Cornwall
- Two-storey front extensions
- Two-storey extensions for end-of-terrace houses
- Two-storey annexe extensions
- Garage conversions with a room above
- Two-storey extension plans and drawings
- Planning permission for two-storey extensions
- Structural engineering for two-storey extensions
- Building regulations for two-storey extensions
- Party wall notices for extensions
- Design and build two-storey extensions
Rules for St Austell
St Austell is in England. Two-storey rear: up to 3 m deep and 7 m from the rear boundary under permitted development. Side, wraparound and front: planning permission. Householder planning application: £548 (or £575 for applications made from 8 December 2026). Lawful development certificate: £274 (about £288 for applications from 8 December 2026). Councils should decide householder applications within 8 weeks of validation.
The full England rules explained
Questions about extensions in St Austell
Do you cover St Austell?
Yes. We cover St Austell (PL23, PL24, PL25 and PL26) and the surrounding area, including Bodmin and Truro. The first site visit is free.
What does a two-storey extension cost in St Austell?
Using our South West England guide, a two-storey rear extension with a 4 m × 3.5 m footprint on two floors (28 m² of new floor space) is about £57,500–£78,000 including VAT. An extension over a garage is about £32,500–£47,500.
Which other places near St Austell do you cover?
Everywhere around it, including Bodmin (9.2 miles), Truro (13.5 miles) and Newquay (14.1 miles), and the rest of Cornwall.