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 Downpatrick?
In Downpatrick, a side extension typically costs £1,450–£2,300 per m² of floor area, including VAT at 20% (standard rate). For a typical 28 m² project that is roughly £40,500–£64,500. Building costs in Northern Ireland run about 14% below the UK average, and the figures for Downpatrick are adjusted to reflect that. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (20 m²) | £29,000–£46,000 |
| Typical project (28 m²) | £40,500–£64,500 |
| Larger project (39 m²) | £56,500–£89,500 |
| Rate per m² | £1,450–£2,300 |
The main things that change the cost:
- Internal fit-out of the new rooms
- Single or two storeys
- Boundary walls and access for materials
- Drains, gas meters or soil pipes that need moving
A guide range is only a starting point: the guide price tool gives an instant figure for your size, and a free survey turns it into a fixed quote.
Do you need planning permission for a side extension in Downpatrick?
Before anything is built in Downpatrick, we confirm which approvals apply in Northern Ireland. In Northern Ireland a single-storey side extension can be permitted development if it is no more than 4 metres high, no wider than half the original house and not beside a wall facing a road. Side extensions of more than one storey need planning permission.
In Northern Ireland building control approval comes from the council, usually through a full plans application or a building notice, with inspections during the work and a completion certificate at the end.
We check this for your address before design work starts, so there are no surprises later.
What we handle
On a typical side extension we handle:
- Structural calculations
- Opening into the existing house
- Electrics, heating and plastering
- Walls, roof and windows to match the house
- Foundations and drainage alterations
- Building control completion
How long does it take?
Expect 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 Downpatrick
Across Northern Ireland, bungalows and chalet bungalows are common, so loft conversions and rear extensions are popular projects.
If your home is in Downpatrick or close by in Newtownards, Lisburn and Belfast, a free home visit is the first step.
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 in place
We handle planning, building control and neighbour notices before work starts.
- 04
Construction and completion
We build, put right any snags and hand over the building control certificate.
Questions about side extensions in Downpatrick
How much does a side extension cost in Downpatrick?
In Downpatrick, a side extension typically costs £1,450–£2,300 per m² of floor area, including VAT at 20% (standard rate). A typical 28 m² project comes to roughly £40,500–£64,500. Your fixed price depends on the survey and drawings.
Do you build side extensions in Downpatrick?
Yes. We build side extensions across Downpatrick, including postcodes BT30. Every project starts with a free home visit.
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.
Do I need planning permission for a side extension in Downpatrick?
In Northern Ireland a single-storey side extension can be permitted development if it is no more than 4 metres high, no wider than half the original house and not beside a wall facing a road. Side extensions of more than one storey 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.
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.