Thermal images have revealed the damp and water damage to Charles Rennie Mackintosh's "domestic masterpiece" is worse than previously thought.

The Hill House in Helensburgh was Mackintosh’s vision of a "home for the future", but decades of wind and rain have caused the sandstone structure to be dissolving under its cement render.

The National Trust for Scotland (NTS), who own and care for the 1904 property, and Historic Environment Scotland (HES) conducted the survey while a giant £4.5million box is constructed to shield the building from the elements.

State of the art infra-red thermographic (IRT) imaging was used to indicate where moisture is retained within the building fabric.

The images, which record differences in surface temperatures, were combined with new 3D digital survey and microwave moisture readings and a previous IRT survey carried out in 2003.