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 Potters Bar?
In Potters Bar, a side extension typically costs £1,800–£2,800 per m² of floor area, including VAT at 20% (standard rate). For a typical 28 m² project that is roughly £50,500–£78,500. Building costs in the East of England run about 6% above the UK average, and the figures for Potters Bar are adjusted to reflect that. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (20 m²) | £36,000–£56,000 |
| Typical project (28 m²) | £50,500–£78,500 |
| Larger project (39 m²) | £70,000–£109,000 |
| Rate per m² | £1,800–£2,800 |
The main things that change the cost:
- Single or two storeys
- Internal fit-out of the new rooms
- Roof design and tile matching
- Boundary walls and access for materials
Use the guide price tool to see how size and specification change the figure, then ask for a written, itemised quote.
Do you need planning permission for a side extension in Potters Bar?
Here is how the rules work for a side extension 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.
We check this for your address before design work starts, so there are no surprises later.
What we handle
From survey to sign-off, the job normally involves:
- Structural calculations
- Walls, roof and windows to match the house
- Survey of the boundary, drains and access
- Planning drawings and application
- Foundations and drainage alterations
- Building control completion
How long does it take?
The build itself usually takes 10 to 16 weeks on site depending on size and storeys. Design and approvals come first and typically take 3 to 4 months, depending on the approval route.
Building in Potters Bar
Many towns in the East of England have estates built since the 1970s, where garage conversions and rear extensions are popular.
Potters Bar sits in Hertfordshire, about 8 miles south-west of Hertford. We cover the whole of Potters Bar, including postcodes EN6.
How it works
- 01
Survey and brief
We visit, discuss your ideas and budget, and survey the property or site at no cost.
- 02
Design and fixed quote
Drawings, structural calculations and an itemised, fixed price for the agreed specification.
- 03
Permissions sorted
Applications, building control and neighbour arrangements, all before the start date.
- 04
Build and sign-off
We run the build to a written programme and hand over the completion certificate.
Questions about side extensions in Potters Bar
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.
Do you build side extensions in Potters Bar?
Yes. We build side extensions across Potters Bar, including postcodes EN6. 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 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 Potters Bar?
In Potters Bar, a side extension typically costs £1,800–£2,800 per m² of floor area, including VAT at 20% (standard rate). A typical 28 m² project comes to roughly £50,500–£78,500. Your fixed price depends on the survey and drawings.