A double-storey extension adds two floors of new space to your house in one build, typically a larger kitchen or living room downstairs with an extra bedroom, bathroom or en-suite above, sharing one set of foundations and one roof.
Anyone planning a double-storey extension in Bangor, County Down wants three things: a clear price, a realistic timetable and a tidy job. We publish a guide of £52,000–£103,000 including VAT for Northern Ireland up front, explain that work normally takes 14–22 weeks on site, and confirm both in writing after a free survey of your property.
- Guide price
- £52,000–£103,000 inc VAT
- Time on site
- 14–22 weeks on site
- Postcodes
- BT19 and BT20
- Planning rules
- Northern Ireland
- Local area
- North Down
- Survey
- Free, with a written quote
What should you budget for a double-storey extension in Bangor, County Down?
In Bangor, County Down, guide figures for a double-storey extension sit at £52,000–£103,000, VAT included. We set them using rates for Northern Ireland, currently about 14% below the national guide. The table shows what pushes a project towards either end of the range; your own price is set after a free survey.
| Type of job | What it usually involves | Guide in Bangor |
|---|---|---|
| Small (15–20m² total) | A compact rear or side extension adding a small room on each floor. | £34,500–£56,000 |
| Typical (30–40m² total) | A larger kitchen or living room below with a double bedroom or en-suite above. | £52,000–£103,000 |
| Large (50m² plus total) | Wide or deep extensions, often with a new bathroom, steelwork and high-spec glazing. | £86,000–£155,000 |
Your price depends mostly on:
- How the new roof joins the existing roof
- Bathrooms, en-suites and plumbing on the upper floor
- Foundation depth, ground conditions and drains to divert
- Scaffolding duration, access and the level of finishes
What’s included?
- Groundworks, foundations and below-ground drainage
- Roof structure tied into the existing roof, tiled to match
- Scaffolding for the full build, erected and inspected
- Electrics, plumbing and heating by qualified trades, with certificates
- Windows, external doors, plastering and internal doors
- Building control inspections and completion certificate
Homes in County Down
County Down takes in suburbs of Belfast, Bangor and Holywood with Victorian and Edwardian villas, and Newry, Downpatrick and Banbridge with older town centres and newer estates. Mourne granite appears in buildings around the mountains, and detached rural homes and bungalows are common across the county, often rendered or pebbledashed.
Coastal areas such as the Ards Peninsula face salt and wind, and the Mournes bring heavier rain and colder conditions.
None of this holds for every street in Bangor, County Down, which is why we look at your actual house before pricing a double-storey extension rather than assuming from its age alone.
Permissions for a double-storey extension in Bangor, County Down
For anyone in Bangor, County Down, the relevant framework is Northern Ireland's. The summary below is general, so we always contact the council about your address before putting a price in writing.
In Northern Ireland, two-storey extensions usually need planning permission from the council.
Building control approval is needed under the Building Regulations (Northern Ireland). There is no Party Wall Act in Northern Ireland.
Rules change and every property is different, so we check the planning history and constraints for your address before we quote.
What happens after you get in touch?
A visit to your home
First, someone visits your home in Bangor, County Down to see the space, take measurements and note anything that could affect the work, such as access or the condition of what is there. There is no charge for this visit.
Your fixed price
We put everything into a written, fixed-price quote: the specification, what's excluded, staged payments and the expected time on site. Take whatever time you need to decide; there's no pressure to commit.
Getting ready
Once you accept, we agree start dates, order materials and deal with any planning, building control or neighbour notices the job needs. You'll know who is coming and when before work begins.
On site to finish
On site, the agreed plan is followed and any change is put in writing first. At completion we do a final clean, go through the snagging list with you and leave you with the relevant documents.
Why homeowners choose us
Frequently asked questions
Who do I deal with during the job?
One point of contact manages your project from survey to handover. They schedule the trades working under our contract, keep you updated on progress, and are the person to call with any question. You don't need to coordinate builders, electricians or decorators separately, because that is part of what we do.
Is a double-storey extension better value than single-storey?
A double-storey extension usually gives better value per square metre than a single-storey one, because the same foundations and roof serve twice the floor area. The overall cost is higher, and planning can be harder because of the effect on neighbours. If you might want an extra bedroom later, building both floors now avoids a second round of disruption and scaffolding.
Can we live at home while it is built?
Most families stay at home during a double-storey extension. The new structure is built outside first, and we only break through into the existing rooms near the end, usually one floor at a time. Upstairs, this may mean a bedroom is out of use for a week or two. We fit dust screens, protect floors and stairs, and plan any time without water or power in advance.
Will the extension affect my neighbours?
A double-storey extension can affect neighbours' light, outlook and privacy, which is why planning departments look closely at height, depth and window positions. Side windows facing neighbours often need obscure glass. Work near a shared wall may also need party wall notices; the Party Wall etc. Act 1996 applies in England and Wales only. We talk through these points early so the design is realistic.
Can you combine a double-storey extension with other work?
Yes. Because we manage several trades under one contract, we can plan a double-storey extension alongside other work on your Bangor, County Down home, such as new windows with rendering, or a kitchen refit with an extension. Combining jobs can reduce repeat set-up such as scaffolding, skips and access, and every element is listed and priced in the same written quote.
Near Bangor, County Down
Homes across BT19 and BT20 in Bangor, County Down are within our coverage, as are those in Newtownards, Carrickfergus and Newtownabbey. If you are just outside these areas, ask anyway, because we work right across the UK.