Controversial extension work on Nutclough Mill is due to be completed by the end of March.
Calrec Audio Ltd was given permission for the works on the site on Victoria Road, Hebden Bridge, in January 2012, despite objections from nearby residents and councillors.
Now the work is nearly complete, Calrec marketing manager Kevin Emmott said he was delighted and said it would safeguard jobs at what is the town’s biggest employer.
“The work will allow Calrec to create a world-class, purpose built manufacturing facility, which in turn will help to safeguard jobs and continue to develop the business,” he said.
Calrec began preparing the foundations of the site in May 2013.
The shell is now completed, with ducting and electrical wiring still to be installed.
The final development is the laying of a green roof.