THE metal box protecting the iconic Hill House in Helensburgh could disappear by 2027, the site's new project manager has revealed.

Liz Davidson gave a presentation to Helensburgh Community Council (HCC) on Thursday night about progress at the site since she was appointed by the National Trust for Scotland (NTS) in December.

Ms Davidson spoke about the "massive research done" on the building and how to turn that into a long-term future for the property.

Designed and decorated by Charles Rennie Mackintosh and his wife, Margaret MacDonald, a century ago, it first had a shell put over it in 2019.

The "chain-mail" box has allowed the building to dry out after decades of damage from the elements.

It has also become a visitor attraction in its own right, with visitors to the house able to look down on the historic building from above.

Water has been getting into the fabric of Hill House for many years and successive owners, most recently the NTS, have spent decades searching for solutions.

Ms Davidson said the NTS hoped to take 'The Box' off in about four years before the 10-year lifetime of the structure expires.

She said: "Water has penetrated the concrete roughcast covering of the house for decades, breaking down the sandstone substrate which lies beneath.

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"This was exacerbated by Mackintosh’s design, which did not feature details that most buildings, especially in the west of Scotland, would have had, such as projecting cills, caps to wallheads and parapets and chimney stacks.”

The NTS will be trialling a new render in May to ensure breathability and flexibility for the building. It would not change the look of the building, but would protect it in a way the original render did not.

Once the damage to the house is stopped, the gardens could also be reinstated and a new visitor centre planned.

Ms Davidson said: "The Box was opened up to the public on Charles Rennie Mackintosh’s birthday in 2019, and since then the fabric of the building has been steadily drying out, thanks to the protection it provides.

"We regularly monitor this with the digital and science team at Historic Environment Scotland with whom we have an ongoing partnership.

"As well as allowing us to monitor and protect the House, its interior and the artefacts within it, the Box has allowed an entirely new perspective on the house itself for visitors and experts viewing the building in its landscape.”

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Ms Davidson was previously a senior project manager involved in the restoration of the Mackintosh Building at Glasgow School of Art.

She will be applying to extend the planning permission for the Box to Argyll and Bute Council in the coming weeks.

She added: "The Box has a limited design life and our original planning application was for five years.

"The pandemic interrupted this programme, so we need to apply for an extension.

"There is no intention to keep the Box any longer than necessary, but it’s doing an important job for us right now.”

The plan to remove and replace the current roughcast will be guided by the condition of the core of the wall, she said.

And stakeholders in Helensburgh and beyond will be kept informed of all future developments.

She said: "The Hill House is considered around the world to be a gem of Scottish architectural history and a masterpiece of design.

"In order to protect it for Scotland and for art and design history, we have embarked on a pioneering conservation project.

"We are very grateful for the support of everyone from the local community, the Mackintosh community, descendants of the Blackie family and the donors and members who have got us to this point where we can start planning the next practical steps needed to conserve this treasure for everyone.”