In the first of a series of blog posts about the major project to conserve Charles Rennie Mackintosh’s Hill House in Helensburgh. Hazel Neill writes about her visit there to meet Business Manager, Fritha Costain on 20thAugust 2018

Hill House was built between 1902-1904, high above the town with views south over the Firth of Clyde. In an example of ‘Total Design’ Mackintosh spent three months living with his clients, the Blackie family, in order to perfect his vision and plan every detail of the exterior and interior fittings and furniture. The house has had two private owners before being taken over by the Architects Society of Scotland and finally acquired by The National Trust for Scotland in 1985.

Before going inside the house, Fritha gave me some background history and outlined some of the inherent structural issues that have been a permanent problem since the building was completed; the greatest being the nature of the construction materials and their constant contact with water…of which there is no shortage in the west coast of Scotland. Indeed, the site, a former potato field with a heavy clay soil, is situated directly beneath a reservoir and at times of heavy rain, water has been seen running through the cellar space.

In compliance of the strictures of the Luss Estate, Hill House was constructed of red sandstone from their quarry with additional sections of the building built with brick, as seen above. A pioneer in the use of innovative technology and materials, Mackintosh eschewed traditional lime render harling and opted for the use of Portland cement render instead.

Frost cracks in this extremely hard, impermeable material have allowed water to permeate and soak into the sandstone since the building was constructed. Over time the dew point within the stone may also have shifted towards the interior of the building creating serious problems with condensation and damp.

Since the National Trust for Scotland took over the care of the building various interventions have been undertaken to address this problem with differing levels of success. Then, in 2015, it was decided that rather than continue with a repair programme it would be far better to initiate a research and development project. The following year Edinburgh based firm, LDN Architects were appointed and the idea of ‘The Box’ was formed.

The Box is a £4.5 million project designed to allow the building to dry out and conservation work to be undertaken. It will be up for a maximum of ten years during which time a research project lasting approximately three years will be carried out. The Box will encase the building and extend up to 2.5 metres around it. It is constructed of a firm steel structure covered in a chain mail of steel mesh with a solid roof. The mesh will allow airflow and insects to circulate but will prevent free water and birds from getting in. It is likely that Hill House will remain visible through The Box in certain lighting conditions, though this remains to be seen.

Rather than prevent access, this project plans to combine conservation with the visitor experience by including a visitor centre on three floors and walkways around and over the top of the building, thereby enhancing appreciation of the house and increasing public awareness of the conservation issues and, as the project progresses, of the solutions developed.

The National Trust for Scotland conservation and architectural heritage teams will seek consultation from conservation professionals, both nationally and internationally, and it is possible that the project may lead to the development of new materials and techniques.

Initial treatments may involve removal of the harling [only 25% of which is believed to be original], installing heating to move the dew point within the sandstone, addressing issues with some of the windows and improving the drainage across the site. Some of the key elements of the collection have been removed and housed offsite.

Officially closed at present, Hill House will re-open in Spring next year.

Thank you to Fritha Costain and The National Trust for Scotland for a fascinating visit.