ONE of the greatest architectural creations of Charles Rennie Mackintosh is plagued with damp prompting fears that the interiors could be affected.
A thermal imaging survey of the Hill House mansion in Helensburgh highlighted the problem in the exterior walls.
And now the National Trust for Scotland (NTS), which owns 106-year-old property, says that it is consulting experts on how to deal with the problem.
It is also considering launching a public appeal for funds to restore the building.
But the Charles Rennie Mackintosh Society is urging immediate action to be taken in case any of the interiors become damaged.
The thermal imaging survey was carried out last year by Historic Scotland on behalf of the NTS.
It found that the traditional Scottish harling applied to the building to protect it from the weather is now cracking and allowing moisture to be trapped.
Maureen Young, the Historic Scotland scientist who conducted the survey, said:
“On the south-facing external wall, thermal imaging located concentrations of moisture below the harling.
“The thermal evidence suggested that moisture penetration problems were most probably due to rainwater penetration behind the harling through cracks.
“Any future strategy will have to balance how best the aesthetics of this exterior are preserved, while also considering how this impacts on the ongoing management of the interiors. “
Terry Levinthal, the Trust’s director of conservation, added:
“The technical complexities of dealing with such serious building issues on a building of such significance are immense.
“That is why the Trust is being very thorough in its research before beginning any work. “
But Stuart Robertson, director of the Charles Rennie Mackintosh society, criticised the lack of immediate action.
“From the society’s point of view, we would like to see things move faster. They [the NTS] have been talking about holding a symposium and having a discussion about it, as there is a view that to take the harling off would damage the integrity of the original building.
“The only way to do it properly seems to be taking quite a lot of the harling off. If you don’t take the harling off to repair it then you start to get the water affecting the integrity of the interior of the building.
“If water comes in to areas where it affects the original wallpaper, you can’t do anything about that. “
The Hill House was completed in 1904 for wealthy Glasgow publisher Walter Blackie.
It now welcomes around 25,000 visitors a year.