See all stories
22 Jun 2023

Digging deep into the condition of the Hill House

Written by Sarah Burnett
Three people in hard hats are on a scaffolding platform, taking a small section out of the wall render on the Hill House.
A team of engineering and conservation specialists have carefully recorded the condition of the walls of the Hill House.
Early conservation findings indicate that action taken by the National Trust for Scotland is slowing down the deterioration of Charles Rennie Mackintosh’s masterpiece.

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.

A view of the Hill House, surrounded by a very large metal, chainmail structure. The view is from the garden and it is a sunny day.
The Hill House Box

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.’

“The protection offered by the Box has allowed this drying out and transformation in structural performance.”
Liz Davidson
Project Director, National Trust for Scotland

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.

The Trust has taken small samples of all the materials found – including a sample of what is believed to be Mackintosh’s original roughcast mix that has survived in one area of the building. Small quantities of all the materials exposed were sent to researchers at the University of Dundee for analysis of their composition and material behaviour.

The most significant result of the work is the finding that the walls, under the roughcast, have been steadily drying and regaining strength in the controlled environment provided by the Box. Further investigation will now commence on a similar exercise working from the inside face of the building, targeting rooms where the damp has been most prevalent historically, including chimney flues and areas below steep parapets.

Meanwhile, the excavations themselves have been neatly sealed up with cover plates. These allow specialist surveyors to revisit each site and steadily explore the questions of what lies beneath the cement jacket of the Hill House.

The drawing room at the Hill House looking towards the fireplace. Next to the fireplace is an upholstered settle; also in the room is an upholstered armchair and a small table.
The beautiful Drawing Room in the Hill House

Philip Long OBE, Chief Executive of the National Trust for Scotland, added: ‘The Hill House is the only original Charles Rennie Mackintosh domestic dwelling open to the public, and over the coming years, the conservation of this internationally renowned and unique heritage asset will be a critical project for our charity. The work to save and conserve the Hill House is a vital and substantial task, and one we won’t be able to undertake without generous support from funding bodies, philanthropists and Mackintosh enthusiasts in Scotland and around the world, whose help we will be appealing for.’

The House came into the care of the National Trust for Scotland in 1982, from which time we have systematically repaired and conserved both interiors and exteriors. However, the experimental materials of the house – in particular Mackintosh’s use of early Portland cement roughcast for its exterior walls combined with non-traditional detailing – has meant that decades of water penetrating and percolating through its fabric has endangered the building’s structure and decoration.

The erection of the Hill House Box, which opened to visitors on 7 June 2019, to shelter and protect the house has dramatically slowed down the effects of water ingress.

Explore the Hill House

Visit now