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 Thatcham?
In Thatcham, a side extension typically costs £1,900–£2,950 per m² of floor area, including VAT at 20% (standard rate). For a typical 28 m² project that is roughly £53,000–£82,500. Building costs in the South East run about 12% above the UK average, and the figures for Thatcham are adjusted to reflect that. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (20 m²) | £38,000–£59,000 |
| Typical project (28 m²) | £53,000–£82,500 |
| Larger project (39 m²) | £74,000–£115,000 |
| Rate per m² | £1,900–£2,950 |
What moves the price most:
- Internal fit-out of the new rooms
- Steel work where the side wall is opened
- Drains, gas meters or soil pipes that need moving
- Roof design and tile matching
For a figure based on your own measurements, try the guide price tool, then book a free home visit for a fixed quote.
Do you need planning permission for a side extension in Thatcham?
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
What we take care of:
- Walls, roof and windows to match the house
- Opening into the existing house
- Foundations and drainage alterations
- Structural calculations
- Planning drawings and application
- Electrics, heating and plastering
How long does it take?
Allow 10 to 16 weeks on site depending on size and storeys. Before that, surveys, drawings and approvals usually take 3 to 4 months, longer if the council asks for changes.
Building in Thatcham
Commuter towns across the South East have many 1930s and post-war semis that suit rear extensions and hip-to-gable loft conversions.
Our Thatcham coverage includes postcode districts RG18, and we also work in nearby places such as Newbury, Basingstoke and Reading.
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 pricing
Design options, then a fixed quote based on the chosen drawings and specification.
- 03
Approvals
Planning or permitted development confirmation, building regulations and any party wall matters.
- 04
Construction and completion
We build, put right any snags and hand over the building control certificate.
Questions about side extensions in Thatcham
Do you build side extensions in Thatcham?
Yes. We build side extensions across Thatcham, including postcodes RG18. Every project starts with a free home visit.
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.
Will a two-storey side extension look odd?
Not if it is designed well. Setting it back from the front and keeping the roof lower than the main ridge usually gives a natural look and is what most councils ask for.
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.
How much does a side extension cost in Thatcham?
In Thatcham, a side extension typically costs £1,900–£2,950 per m² of floor area, including VAT at 20% (standard rate). A typical 28 m² project comes to roughly £53,000–£82,500. Your fixed price depends on the survey and drawings.