Does a garage conversion need Building Control approval in Northern Ireland?

Building Control: yes, always. Turning a garage into a habitable room changes its use, and the converted space must meet the Building Regulations standards for a living area: floor insulation and damp-proofing, wall and roof insulation, ventilation, fire escape provision, and certified electrical work. You apply to your council’s Building Control department, inspectors visit at stages, and you receive a completion certificate at the end, the piece of paper your buyer’s solicitor will one day ask for.

Planning permission is the separate question, and the answer is often no: where the conversion keeps the existing structure and the external appearance barely changes, many garage conversions proceed without a planning application. But "often" is not "always", integral versus detached garages, previous extensions, and location can all change the position, so a quick call to your council’s planning office before you start is the cheap insurance. Our planning guide covers how to check.

On cost, a garage conversion is usually the cheapest way to add a room in NI: our researched 2026 benchmarks put it at £800 to £1,100 per square metre for a budget specification, £1,100 to £1,400 mid-range, and £1,400 to £1,800 premium, well below extension money because the shell already exists.

The trap to avoid is the informal conversion: no Building Control, no certificates, plasterboard over problems. It surfaces at sale time as a room the survey cannot count, and regularising it retrospectively costs more than doing it right the first time.