A single-storey extension is a new ground-floor room built onto your house, usually at the rear or side, with its own foundations, walls and roof, creating a bigger kitchen, living space or bedroom without moving home.
From Derry/Londonderry, Coleraine, Limavady and Magherafelt to the quieter corners of County Londonderry, homeowners can book a free survey for a single-storey extension. We look at the building, agree the scope, then send a quote in writing that fixes the cost of that scope. Work follows the rules for Northern Ireland, and our published range for Northern Ireland, £30,000–£64,000 with VAT, gives you a sense of budget before we visit.
- Guide price
- £30,000–£64,000 inc VAT
- Time on site
- 10–16 weeks on site
- Planning rules
- Northern Ireland
- Price level
- About 14% below the national guide
- Towns listed
- 4
- Survey
- Free, with a written quote
Single-storey extensions prices in County Londonderry
These are guide costs, not quotes. For a single-storey extension in County Londonderry the range is £30,000–£64,000, VAT included, reflecting prices in Northern Ireland that are about 14% below the national guide. Once we have visited for a free survey, you get a firm figure for the scope you approve.
| Type of job | What it usually involves | Guide in County Londonderry |
|---|---|---|
| Small extension (8–12m²) | A modest rear or side extension, such as a utility room or a slightly larger kitchen. | £19,000–£34,500 |
| Typical rear extension (15–25m²) | A kitchen-diner or family room with bifold doors and a rooflight or lantern. | £30,000–£64,000 |
| Large or wrap-around (30m² plus) | A wrap-around or wide rear extension, often with structural steelwork into the house. | £60,000–£112,000 |
What moves the price up or down:
- Roof type, rooflights, lanterns and the amount of glazing
- Ground conditions, foundation depth and drains to divert
- Steelwork needed to open into the existing house
- Finishes, kitchen, flooring and heating specification
What’s included?
- Flat or pitched roof, with rooflights or a lantern if specified
- Steel beams to open into the existing house
- Electrics and plumbing by qualified trades, with certificates
- Windows and external doors, including bifolds if chosen
- Plastering, screed floor and internal doors
- Building control inspections and completion certificate
Housing across County Londonderry
Derry has Georgian and Victorian terraces around its walled city, alongside large post-war estates and newer developments. Coleraine, Limavady and Magherafelt mix older town centres with semis and estates, Portstewart has seaside villas, and rural areas have many detached homes and bungalows, often roughcast.
Terraces suit loft conversions and rear extensions, while rural bungalows commonly take extensions, loft rooms and driveways. Roughcast homes often need re-rendering, and coastal houses need roofline and window renewal.
The north coast faces Atlantic wind, rain and salt, and the Sperrins inland are colder and wetter.
Planning and building rules in County Londonderry
Homes in County Londonderry come under the regulations for Northern Ireland, summarised below. We don't rely on general rules alone: we confirm the position for your address with the council before a quote goes out.
In Northern Ireland, permitted development allows many single-storey rear extensions, typically up to 3 m deep on attached houses and 4 m on detached houses, within height and garden-coverage limits. Conservation areas, listed buildings and side extensions are more restricted.
Building control approval under the Building Regulations (Northern Ireland) is needed for extensions. Northern Ireland has no Party Wall Act, so boundary work is agreed with neighbours directly.
Rules change and every property is different, so we check the planning history and constraints for your address before we quote.
The four stages
A visit to your home
We begin by looking at the job in person. During the free survey we discuss options, materials and budget for a single-storey extension, and photograph or measure anything the quote needs to reflect.
Price and scope agreed
You get the price in writing, itemised so you can see where the money goes. As long as the specification stays the same, that is the price you pay for a single-storey extension.
Plan and prepare
Before anyone starts, we confirm the programme in writing, check whether consents are required and arrange deliveries. If a skip or scaffolding on the road needs a permit, we apply for it.
Finish and handover
Our trades complete a single-storey extension while your point of contact keeps you updated. When everything is finished, we clear the site, take away waste and go through the result with you before handover.
How we work
Questions about a single-storey extension in County Londonderry
Do you cover Derry/Londonderry, Coleraine and Limavady?
Yes. As well as County Londonderry, we cover Derry/Londonderry, Coleraine and Limavady and the rest of County Londonderry. Our coverage is UK-wide, so the process is the same wherever you are: a free site survey, a quote in writing that fixes the price for the agreed scope, and one point of contact while the work is planned and carried out.
Can you combine a single-storey extension with other work?
Yes. Because we manage several trades under one contract, we can plan a single-storey extension alongside other work on your County Londonderry 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.
What does a typical extension build look like week by week?
A typical single-storey extension follows the same order: clearing the site and digging foundations, building walls up to roof level, then fitting the roof and windows to make it weathertight. Electrics, plumbing, insulation and plastering follow. The last stage is opening into the house, laying the screed and fitting doors and finishes. Building control inspects at key stages, and we book those visits for you.
Can we stay at home during the build?
Most people stay at home while we build a single-storey extension, because the new structure goes up outside before we break through. The disruptive part is usually the last few weeks, when we open into the house and fit the kitchen. We put up dust screens, keep a safe route through the house and agree a temporary kitchen setup if needed. Water and power are only off for short, planned periods.
Is a flat roof or a pitched roof better on an extension?
A flat roof is quicker to build and usually costs less, gives a clean modern look and works well with a roof lantern. A pitched roof matches the main house, sheds water faster and allows a vaulted ceiling, but it costs more and its height can affect neighbours. Modern flat roofs in EPDM rubber or GRP last well when properly detailed. Planning rules on height can also decide the choice.
Towns in County Londonderry
Looking for a single-storey extension somewhere in County Londonderry? Start with the towns below; each links to a page with pricing for your region and coverage details.