WARDS are being merged at St Luke's Hospital to prepare for the big move.
Patients from the Crosland Moor site are being moved to Huddersfield Royal Infirmary after plans to modernise mental health services were agreed last year.
It is expected the move will take place in about two years.
In the meantime, plans are under way at St Luke's to join Ward 4 patients - who suffer conditions including severe depression and schizophrenia - with those on the Dementia Care Unit.
A conservatory is being built on to the unit to accommodate the extra patients from April.
But the plans to spend more cash on the building, which is earmarked for demolition, have come under fire.
Concerns have also been raised about mixing vulnerable patients.
Karen Norgate-Senior, whose mother Pat Norgate was a dementia patient at St Luke's, said: "The management vision is totally different to the staff and patient needs.
"These are two completely different patient groups with very different needs.
"The health trust is running a deficit, so why are they spending money when they are going to be moving out and the building is going to be demolished? It just seems silly."
Her mother, from Meltham, was a patient in the DCU when she died in January.
Karen, 34, of Gomersal, praised the care she received.
She said: "The nursing care has been excellent, making sure that mum didn't have a bedsore, even though she was immobile for four years.
"These people nurtured her, loved her and laughed for her, sometimes managing to gain a rare and precious smile.
"They offered to bring her to my wedding until she was so ill she could not make it.
"They became an extended family for us, providing support when things got too much.
"If we had been millionaires we could not have had better care for our mum."
Karen fears care standards could suffer under the proposed changes.
A spokesman for South West Yorkshire Mental Health Trust, which is responsible for St Luke's, said: "The new ways of working mean we need fewer beds, with staff helping people in their own homes and in other local settings, such as nursing homes.
"Because we need fewer beds both wards at St Luke's have been running with reduced occupancy.
"The decision was therefore taken to combine the services from April.
"The trust will work hard to make sure that patients will not be disadvantaged by a mixed care environment.
"There is already a mixed ward for functionally ill and dementia care patients in Dewsbury and we are learning from staff there about how best to plan our new service.
"We need to provide the best care we can for older people in Huddersfield.
"Working in this new way will help us do this and make us well prepared for the move to HRI when it happens."