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 Coulsdon?
In Coulsdon, a side extension typically costs £2,200–£3,450 per m² of floor area, including VAT at 20% (standard rate). For a typical 28 m² project that is roughly £61,500–£96,500. Prices across London are typically 30% above the UK average for this kind of work, which is reflected in the range for Coulsdon. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (20 m²) | £44,000–£69,000 |
| Typical project (28 m²) | £61,500–£96,500 |
| Larger project (39 m²) | £86,000–£134,500 |
| Rate per m² | £2,200–£3,450 |
Your quote will depend mainly on:
- Drains, gas meters or soil pipes that need moving
- Boundary walls and access for materials
- Internal fit-out of the new rooms
- Roof design and tile matching
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 Coulsdon?
Approvals for a side extension in Coulsdon follow the rules for 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.
Where work involves a shared wall, building on the boundary, or digging foundations within 3 metres of a neighbour’s building and deeper than its foundations (or within 6 metres for deeper work), the Party Wall etc. Act 1996 applies and notices must be served before work starts.
Our first visit includes a check of your planning history, so you know the route before paying for drawings.
What we handle
From survey to sign-off, the job normally involves:
- Walls, roof and windows to match the house
- Opening into the existing house
- Structural calculations
- Survey of the boundary, drains and access
- Foundations and drainage alterations
- Electrics, heating and plastering
How long does it take?
The build itself usually takes 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 Coulsdon
Many London boroughs have conservation areas and detailed design guides, so early design advice saves time at the planning stage.
Projects in Coulsdon (CR5) are surveyed in person before we quote, so the price reflects your actual property.
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
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 Coulsdon
Do you build side extensions in Coulsdon?
Yes. We build side extensions across Coulsdon, including postcodes CR5. Every project starts with a free home visit.
How close to the boundary can I build?
You can build up to the boundary, but the eaves height near it is limited under permitted development, and planning officers often want a gap at first floor. If you build on or near a shared boundary, party wall rules may apply.
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.
Will I lose my driveway?
A side extension often takes the side drive. We look at whether parking can be kept at the front and whether a dropped kerb is needed.
How much does a side extension cost in Coulsdon?
In Coulsdon, a side extension typically costs £2,200–£3,450 per m² of floor area, including VAT at 20% (standard rate). A typical 28 m² project comes to roughly £61,500–£96,500. Your fixed price depends on the survey and drawings.