Children at a free school have taken their first look around what will become their new home.

In January, the Rainbow Primary Free School will move from its current base in the old Belle Vue Girls’ School building in Manningham Lane, Bradford, to a new £4 million facility on the site of a derelict fire station.

The move will allow it to quadruple the number of children it can teach.

Bradford’s 40-year-old Nelson Street fire station is being remodelled into a two-storey school, which will have a distinctive prism-shaped room at its centre where children can congregate.

Amjad Pervez, chairman of the Rainbow Schools Trust, said the cost of the work had risen from £3.2 million to £4 million because of some unexpected building problems – additional work had been needed to make some cellars safe.

Mr Pervez said such hitches would be expected in any regeneration of an old building.

He said: “It’s not gone over budget in that capacity. It was an old building and they needed to make sure everything was safe and sound.”

Free schools are funded by the state but run independently of local authorities. Rainbow was the first primary free school to open in Bradford, in September 2011, and was rated good in its first Ofsted inspection.

It currently has 130 pupils from reception age to Year Four, with Year Five starting in September.

The move to Nelson Street will allow the school to expand to 525 pupils.

Rainbow’s school councillors – pupils aged five to nine who represent their respective year groups – yesterday had a tour of the site, accompanied by staff.

Mr Pervez said: “This is a great day, when we can show the children the wonderful new building they will move to in January, 2014.

“Our pupils are already thriving in Rainbow, as the Ofsted report demonstrates. At the new site, which will have its own sports hall and state-of-the-art facilities indoors and outdoors, they will really fly.”

Councillor Ralph Berry, Bradford Council’s executive member for children’s services, said there was a shortage of school spaces in the Nelson Street area which the expansion of Rainbow Primary would help to address.