What is a side extension?
A side extension builds into the space beside a semi-detached or detached house, often over a driveway or side passage. It can be single-storey, for a utility room, downstairs toilet or study, or two-storey to add a bedroom above.
How much does a side extension cost in Penzance?
In Penzance, a side extension typically costs £1,750–£2,700 per m² of floor area, including VAT at 20% (standard rate). For a typical 28 m² project that is roughly £49,000–£75,500. Prices in the South West sit near the national average for this kind of work, and the range for Penzance reflects that. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (20 m²) | £35,000–£54,000 |
| Typical project (28 m²) | £49,000–£75,500 |
| Larger project (39 m²) | £68,000–£105,500 |
| Rate per m² | £1,750–£2,700 |
Your quote will depend mainly on:
- Drains, gas meters or soil pipes that need moving
- Single or two storeys
- Roof design and tile matching
- Steel work where the side wall is opened
Your exact price depends on the survey and drawings. The guide price tool gives a quick range in the meantime.
Do you need planning permission for a side extension in Penzance?
Whether you need planning permission depends on your house and its location in England. In England a single-storey side extension can be permitted development if it is no more than 4 metres high and no wider than half the width of the original house. Side extensions of more than one storey always need planning permission, as do side extensions in conservation areas, National Parks and National Landscapes.
Building regulations approval comes from the council’s building control service or a registered building control approver. The work is inspected at key stages, such as foundations, drainage and insulation, and a completion certificate is issued at the end.
Our first visit includes a check of your planning history, so you know the route before paying for drawings.
What we handle
Handled as part of most side extensions:
- Survey of the boundary, drains and access
- Structural calculations
- Opening into the existing house
- Electrics, heating and plastering
- Building control completion
- Planning drawings and application
How long does it take?
Allow 10 to 16 weeks on site depending on size and storeys. Allow time beforehand for drawings and approvals, usually 3 to 4 months.
Building in Penzance
In parts of the South West, protected landscapes and conservation areas shape what can be built, so materials and roof forms are chosen carefully.
We work across Penzance and neighbouring areas such as Camborne, Redruth and Falmouth. Postcodes we cover in Penzance include TR18.
How it works
- 01
Free visit
We look at the property, talk through what you want and measure up. There is no charge and no obligation.
- 02
Drawings and written quote
We prepare the design and give you a written, itemised quote with inclusions and exclusions.
- 03
Approvals
Planning or permitted development confirmation, building regulations and any party wall matters.
- 04
Build and handover
Work follows the agreed programme, with inspections along the way and a completion certificate at the end.
Questions about side extensions in Penzance
Can I build a side extension without planning permission?
In England a single-storey side extension can be permitted development if it is no more than 4 metres high and no wider than half the original house, and the house is not in a conservation area or similar protected land. Two-storey side extensions always need planning permission.
How much does a side extension cost in Penzance?
In Penzance, a side extension typically costs £1,750–£2,700 per m² of floor area, including VAT at 20% (standard rate). A typical 28 m² project comes to roughly £49,000–£75,500. Your fixed price depends on the survey and drawings.
Do you build side extensions in Penzance?
Yes. We build side extensions across Penzance, including postcodes TR18. Every project starts with a free home visit.
How long does it take?
Roughly 10 to 16 weeks on site once approvals are in place, depending on whether it is one or two storeys.
Can a side extension go over a drain?
Often yes, with a build-over agreement from the water company or by rerouting the drain. We check this during the survey.