Digging deep into the condition of the Hill House

The Hill House was designed by Mackintosh in 1902–04 for the publisher Walter Blackie and his family. It represents his largest and most complete domestic work, designed at the height of his architectural powers in a striking fusion of proto-modernism and Scots baronial styles. The trademark Art Nouveau and symbolist interiors were developed in partnership with his wife and fellow artist Margaret Macdonald.

Four years ago, our charity erected an architect-designed, award-winning steel cage – the Box – to protect the Hill House from rain and damp, allowing the walls to dry out. Specialists could then start work to stabilise the building to ensure its long-term survival.

A trial to carefully remove small areas of render from the A-listed building’s exterior has shown that the walls, which had begun to show signs of water ingress as soon as 15 years after its completion, are steadily drying and regaining strength. We have welcomed these results as we embark on the next stage of our pioneering project to save the Helensburgh house for Scotland and Mackintosh enthusiasts all over the world.

Liz Davidson, the National Trust for Scotland’s Project Director for the Hill House, stated: ‘These works at the Hill House will help us establish the properties of the materials used by Mackintosh and subsequent repair projects. This in turn will allow us to identify the most appropriate replacement materials to keep the building free of the persistent damp that has threatened its stunning interiors, such as the original stencilling by Mackintosh’s wife Margaret Macdonald.’

Liz continued: ‘But all of us working on this important building are aware that the clock is ticking on being able to embark on permanent repairs and conservation before the shelter of the Box is removed in compliance with planning rules. We’re delighted with the initial research findings but remain very much aware of the scale of the conservation task ahead.’

A team of engineering and conservation specialists have carefully recorded the condition of the walls and have overseen the excavation of areas around the building to examine the core of Mackintosh’s construction. The team meticulously removed the Portland cement roughcast in six locations around the building to reveal the substrate beneath, including what is thought to be the original damp-proof course, red sandstone and brick walls as well as details of some of the repairs made in the last century.