How Much Does a Garage Conversion Cost in Northern Ireland?

Converting a garage is the cheapest square metre you will ever add to a Northern Ireland house: typically £7,500 to £18,000 for a single garage. The walls and roof are already there, so most of the cost is the floor, the insulation, the heating and whatever you do with the door.

Rates last reviewed 1 August 2026 · how we work these figures out

What sort of garage is it?

An integral garage is already inside the thermal envelope of the house, which makes it the cheapest to convert.

Where is the garage?

Integral Built into the house, under the same roof. The cheapest to convert. Attached At the side of the house, sharing one wall. Detached Standalone in the garden. Needs its own heating, services and full insulation.

What condition is it in?

Sound and dry Solid walls, watertight roof, no damp. Some damp Damp patches, a leaking gutter, or condensation on the walls. Poor Failing roof, cracked slab, or single-skin walls that need lining out fully. Not sure We will allow a small margin for the unknown.

How big is it?

Measure inside the garage. A typical Northern Ireland single garage is about 2.6m by 5.5m.

Width

Length

Internal floor area 0 m²

What happens to the garage door?

This changes both the cost and how the finished room feels from the street.

Garage door

Keep the door An insulated wall is built behind it. Cheapest, but the room gets no natural light. Block it up with a window Recommended New blockwork infill, matching finish outside, and a standard window. Block it up with French or bi-fold doors A full-width glazed opening. Best result, highest cost.

Standard of finish

Basic Habitable and warm, builder's standard throughout. Standard Recommended Matches the rest of the house. Proper joinery and decoration. High end Underfloor heating, engineered flooring, built-in joinery.

Where is the house?

Your postcode sets the regional labour rate.

Postcode

The first part is enough. We only use it to pick a regional rate.

What this includes

Insulated lining to the existing walls and roof, plasterboard and skim
Blocking up or infilling the garage door opening
Electrics, lighting and sockets to habitable standards
Internal joinery, skirting, a new internal door and decoration
Building control approval, professional fees and contingency

What it does not include

Rebuilding a structurally unsound garage or replacing failed foundations
Asbestos cement roof sheets, which need licensed removal and are common on older NI garages
Planning permission where a condition or covenant requires the parking space to stay
Any drainage that has to be dug and connected outside the garage footprint
Furniture, blinds and loose fittings

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Questions

Garage conversion costs: the questions people actually ask

How much does it cost to convert a garage in Northern Ireland?

A single garage conversion in Northern Ireland typically runs from about £7,500 for a basic room to around £18,000 for a well-finished space with an insulated floor, heating and a new window in place of the door. A double garage is close to twice the floor area, so budget proportionally more. These figures include VAT, building control and a contingency, and are priced roughly 15 per cent below the UK average, which is where Northern Ireland sits.

Do I need planning permission to convert a garage in Northern Ireland?

Converting a garage inside its existing walls is normally permitted development in Northern Ireland, so planning permission is usually not required. The two things that catch people out are planning conditions on newer estates that require the off-street parking space to be retained, and restrictive covenants in the title deeds that say the same. Check both before you spend anything. Building control approval is a separate process and is always needed, because you are creating a habitable room.

Why does the floor cost so much in a garage conversion?

A garage floor is usually a thin unheated slab, laid 100 to 150 millimetres below the house floor level and often laid to fall towards the door so rain runs out. To make it habitable it needs a damp proof membrane, insulation to current building regulations, and a screed or a floating floor deck to bring it level with the rest of the house. That build-up is typically £55 to £95 per square metre and it is not optional.

Should I keep the garage door or block it up?

Blocking it up costs more but is almost always the better answer. A retained garage door with an insulated wall built behind it keeps the house looking like it still has a garage, which some estate agents like, but you lose the light and the room reads as a converted garage from the street. Infilling the opening with a matching wall and a proper window or French doors is what makes the room feel like part of the house.

Will converting my garage reduce the value of my house?

Usually the opposite, provided you are not removing the only off-street parking. In Belfast and the commuter towns, a fourth bedroom, a home office or a family room is worth more than a single garage that most people use for storage. Where it can go wrong is a terraced or city-centre property on a street with resident parking pressure, where losing the parking space genuinely costs you buyers.