Intruders got into the disused Avala Park Residential Home on Mile Road, Widdrington, and ripped out copper piping, taps, cabling and copper cylinders from 36 rooms.
The burglary, together with the damage caused to the building, is valued at £200,000.
Police are appealing for witness to the crime, which happened between 1am and 1.40pm on Saturday, July 23.
Neighbourhood Acting Inspector Mick Aspey said: "We're appealing for witnesses to this burglary which has also caused a huge amount of damage to the premises when the copper was ripped out the building.
"We're also appealing for anyone who may be offered similar copper items for sale to contact police."
Anyone who was in the area and who may have seen or heard anything suspicious is asked to contact police on 101, quoting reference number 735 of 23/07/16 or ring the independent charity Crimestoppers on 0800 555111.