What an extension actually costs in 2026

A thirty square metre single-storey rear extension in Denver came in between four thousand six hundred and six thousand one hundred dollars a square metre across the last twenty we priced. That is finished, with a kitchen, not a shell.

What moves it most

The ground, first. A straightforward strip foundation is a few thousand dollars. Piling because of a tree or a made-up ground is twenty. Nobody knows which you have until somebody digs a hole, which is why we dig one before we finalise a price where we can.

Glazing, second. The difference between a standard set of doors and a large structurally-glazed opening is routinely thirty thousand dollars, and it is the item clients most often do not realise they have specified.

Access, third. If everything has to come through the house, add fifteen per cent to the labour and a fortnight to the programme.

What barely moves it

The things people agonise over. Tile choice, paint, ironmongery, the exact brick. Real money, but rarely more than three or four per cent of the total, and they are the decisions people spend the most time on.

The honest advice

Spend your decision-making time on the structure and the openings, get the ground investigated early, and choose the kitchen before week two. Everything else will look after itself.