Garden Room and Garden Office Costs in Northern Ireland

Budget roughly £1,800 to £3,800 per square metre in 2026, so a typical 12 square metre garden office lands somewhere around £24,000 to £42,000 fully finished, and a small 8 square metre studio around £17,000 to £24,000. The spread is wide because the phrase covers everything from an insulated timber box to a building specified like a small house. The cheap end of the market is usually thin insulation and single glazing, which is fine for storage and miserable in a Northern Ireland February.

Usually not, if it stays within permitted development. The rule that catches most people is height: within two metres of a boundary the total height must not exceed 2.5 metres, measured to the highest point of the roof. Further from the boundary you get more height. The outbuilding must also be single storey, behind the front elevation, not used as self-contained living accommodation, and must not cover more than half the garden. Conservation areas and listed buildings have tighter rules, so check with your council.

A single storey detached outbuilding under 30 square metres, containing no sleeping accommodation and either more than a metre from a boundary or built substantially of non-combustible material, is generally exempt from building control in Northern Ireland. Add a bed, or go over 30 square metres, and it is no longer exempt. If you intend to use it as an annexe or a guest room, assume you need approval and price it in from the start.

Enough to be usable in January, which is the whole point. As a working target, aim for at least 100 millimetres of rigid insulation in the walls and roof, 100 in the floor, a proper vapour control layer on the warm side and airtight taping at the junctions. That is roughly the standard of a new house extension. Anything thinner and you will be running an electric heater constantly, which quietly costs more than the better specification would have done.

Ground screws are quicker, cause far less mess, need no concrete curing time and work well on the soft, wet ground that is common across Northern Ireland. A reinforced concrete raft is more expensive and more disruptive but is the right answer on unstable ground, on a slope, or where the building is heavy. Either way, the base is a real cost of £60 to £150 per square metre and should never be assumed to be included in a headline price.

Yes. Garden buildings supplied and erected for a domestic customer are standard-rated, and Northern Ireland suppliers quote inclusive of VAT at 20 per cent, so these figures are directly comparable with the quotations you will be given. Be careful comparing a supply and erect price against a kit price: kits are quoted for the building only, and the base, the electrical supply from the house and the internal finishes are all extra. By the time those are added, a kit that looked several thousand pounds cheaper often is not. Ask every supplier what their price includes before you compare the numbers at all.