Historic Salts Mill is undergoing significant repair in its 150th birthday year.

The roof of the former four-storey spinning mill, which faces the railway line, is being stripped and re-covered in Welsh slate to stop it leaking in bad weather.

The work is being done in three phases. At present a third of the building at the Victoria Road end is covered with scaffolding.

Robin Silver, managing director of Salts Estates, declined to be drawn on the cost of the work - believed to be six or seven figures - but told the T&A: "It's the biggest individual building work undertaken at Salts Mill probably since it was built."

Salts Mill was formally opened on September 20, 1853 - the 50th birthday of its owner Titus Salt.

It was a state-of-the-art textile manufacturing operation which linked Bradford to both Peru and Australia.

The mill was closed down in 1986 by its then owners Illingworth Morris.

Bradford-born entrepreneur Jonathan Silver bought it and re-opened the mill as a David Hockney art gallery in November 1987.

In the next ten years Mr Silver, who died aged 47 in 1997, greatly expanded the mill's cultural and commercial activities.

A mixture of culture, commerce and conservation won the Mill and the village top national and international awards, culminating in World Heritage Status, granted by UNESCO on December 14, 2001.

"Heritage doesn't grow on trees," Mr Silver said. "The replacement of the roof is a very major and significant addition to the mill's architectural heritage and has been on the cards for some time.

"We are very pleased that the contractor - Brenville Construction - is a Bradford company, which means work and jobs for people locally, and that the architect, Waller & Co, is local too.

"Work will go on for most of this year. Every effort will be made to inconvenience visitors, tenants and staff as little as possible," he added.