What Does a Loft Conversion Cost in Northern Ireland?

Most Northern Ireland loft conversions land between roughly £25,500 and £63,750 in 2026, including VAT, fees and contingency. A simple rooflight conversion in an attic that already has the head height sits at the bottom of that range, a rear dormer in the middle, and a hip-to-gable or mansard at the top. Northern Ireland runs about 15 per cent below the UK average for this work, almost all of it on labour, which is why national calculators overstate the figure here.

As a working rule you want at least 2.2 metres from the top of the existing ceiling joists to the underside of the ridge before you start. The new floor build-up and the insulation between and under the rafters will take 250 to 350 millimetres of that. If you have less than 2.2 metres, a conversion is not impossible, but it means altering the roof — a dormer, a mansard, or lowering the ceilings on the floor below — and the cost changes category rather than creeping up.

Many rear dormers and rooflight conversions fall within permitted development in Northern Ireland, but the rules come from the Planning (General Permitted Development) Order (Northern Ireland) and differ from the English rules you will find on most UK sites. Anything on the front roof slope, anything in a conservation area, and anything on a listed building or a flat will need permission. Building control approval is separate and is always required, because you are creating a habitable room.

Usually, yes, provided the result is a genuine bedroom with proper head height and a compliant staircase rather than a glorified attic room. In Belfast, adding a fourth bedroom and an en-suite to a three-bedroom semi is the conversion that pays back best. A room that cannot legally be described as a bedroom — no protected escape route, or not enough head height — adds far less, and estate agents will list it as a storage or hobby room instead.

Because it is rarely just a staircase. Building control wants a compliant rise and going, adequate head height over the flight, a protected escape route down to the front door and usually fire doors to every room off it. If the new flight cannot sit directly over the existing one, you are taking space from a bedroom or a landing, moving a partition and making good ceilings and floors on the storey below. That is why the position of the stairs moves the price by several thousand pounds.

Yes. Converting a loft in an existing home is standard-rated for VAT, and Northern Ireland builders quote domestic customers inclusive of VAT at 20 per cent, so these figures match the quotes you will actually receive rather than sitting a fifth below them. The only common exception is a property that has been empty for more than two years, where a reduced rate of 5 per cent can apply to residential renovation work. If that is your situation, get it confirmed in writing by your builder and by HMRC before you rely on it, because the conditions are specific and the paperwork has to be right from the start.