The Hill House Box ​– your questions answered

We’ve launched an urgent appeal to build the Box around Mackintosh’s Hill House in Helensburgh, to help save this iconic building.

What is the Hill House Box?

The Hill House Box is the National Trust for Scotland’s innovative solution to the problem of water damage at the Hill House. Since 1902 the Hill House has been battered by 193 days of rain per year (on average). Sadly Mackintosh’s experimental design, coupled with his trial of new materials, has meant the house now shows signs of serious deterioration. The Box will act as a giant shield covering the entire building, protecting it from the rain while allowing the house to dry out and our conservators to begin their work rescuing this iconic home.

Why now?

Various attempts by previous owners, as well as by the Trust and our partners, have been made to protect the Hill House and repair the cement harling that covers the outside of the building. Sadly, none of these solutions has proved permanent. Since 2018 is the year of Mackintosh’s 150th birthday, and because the water damage is worsening every year, we’ve taken the bold step to take decisive action to save the house and its irreplaceable collection.

What will it be made from?

The Hill House Box will be a semi-transparent shelter around the main house, consisting of a steel roof and a frame encased in a semi-permeable metallic mesh. It has been designed specifically for the Hill House, meaning that the garden within the Box is maintained and protected (trees will continue to grow inside the Box), as well as allowing the building to remain visible.

How will it work?

The shape of the Hill House Box is specifically designed to minimise the amount of rain reaching the building, particularly its upper levels and flat surfaces where water can do a lot of damage. The ‘skin’ chosen for the walls is important: we’ve chosen a mesh designed to collect any rain, while allowing good airflow to the house.

It may come as a surprise to some that we’re not planning to stop 100% of the rain reaching the Hill House. In conservation projects like this, it’s important to maintain the environment that the building and its interiors are used to. If we didn’t do this, the building would be at risk of ‘environmental shock’ and may be damaged further. Instead, we will stop around 87% of the rain reaching the house, allowing it to dry out at a natural rate and at lowest risk of further damage.

What happens once it’s built?

Once the house is protected from the rain, we can start the process of drying the building out naturally. We will then, with the support of international organisations such as The Getty Foundation and our specially appointed advisory panel, be able to understand the extent of the damage caused by the water, and begin to take corrective steps.

How long will it be in place?

It may take up to three years for the house to dry out fully before we can begin our conservation work in earnest. We will then need to develop a long-lasting solution, and implement it. This means the Hill House Box may be in place for up to ten years.

What will it be like for visitors?

We’re extremely excited that the Hill House Box will provide a brand-new way to experience the Hill House. The house will be closed while we construct the Box, but only for a short period. After that it will reopen as usual.

The Hill House Box’s design includes several walkways around the upper levels and over the roof. These will provide a totally new way to experience the house and Mackintosh’s design, as well as offering stunning views over the Clyde estuary. We’ll also build a new café and visitor centre, meaning even more people can experience the house and learn about Charles and Margaret Mackintosh and the Blackie family whom the house was built for.

Has this been done before?

There are other examples of conserving historic buildings in a similar way, but there are two elements that make this project unique.

First is the Box itself. Usually unsightly scaffolding would be erected for projects like this. Instead, the Trust is respecting Mackintosh’s design legacy by delivering an innovative solution that is respectful and design-led.

Secondly, most conservation work of this nature takes place on much older buildings – like medieval castles. The Hill House Box will be a global first in conserving a 20th-century building in this manner, making it a significant project for building conservation around the world.

What’s the cost?

The cost to build the Hill House Box is £4.5 million. £3 million has already been secured, and in February 2018 we launched our biggest appeal to date to raise the final £1.5 million.

We’re still seeking support to build the Box this summer. The appeal has had an incredible response so far, but we’ve still a long way to go!