The three surveys allow building conservators to pinpoint areas of damp, and further understand the declining condition of the property.
Richard Williams, NTS general manager for Glasgow and West Scotland, said they would provide a “robust baseline” for the building’s condition before the protective shield is completed.
He said: “These surveys reinforce what we already knew about the house, which is that it is very damp and has considerable issues that need to be overcome. Due to the design of The Hill House, there are many ledges, wall heads and chimneys that have had a history of many attempts to remedy, yet this problem continues.
“We also now have additional areas of concern, such as large sections of harling that have become disengaged from the walls where damp is accumulating, and internal walls we hadn’t realised were so damp.
“We have also been able to see the direction that the water is travelling in some of the rooms, in particular in the exhibition room, where there was already clear damage.”
He said the construction of the box was “well underway” and it would provide “a temporary respite” pending a long-term solution being found to the building’s problems.