The Hill House Box

The Hill House is a Category A Listed house within Helensburgh, Argyll & Bute, that was designed by Charles Rennie Mackintosh for the publisher Walter Blackie in 1902. It was donated to the National Trust for Scotland in 1982. The house is open to visitors throughout the year.

The aim of the ‘Big Box and Visitor Centre’ project was to provide a stable environment for the conservation of the structure, and space for an innovative, compelling and popular visitor experience which has building conservation and the Mackintosh story at its core.

The structure is a large trussed steel frame over the existing house, with a lightweight polycarbonate roof and a mesh cladding. There is a steel walkway within the structure at various levels forming part of the visitor experience.

Atelier Ten’s fire engineering works involved carrying out a fire risk assessment on the means of escape on the walkway, structural protection and external fire spread assessment for the project.

The means of escape assessment in the building was carried out using PD 7974:2001 Application of fire safety engineering principles to the design of buildings. The intention of the assessment was to determine the risk associated with a possible fire from the existing building affecting occupants on the walkways using computation fluid dynamic (CFD) modelling and evacuation modelling.

The structural protection assessment was carried out using CFD modelling to determine the likely temperatures which the steelwork would be exposed to in lieu of constructing the walkway as per the prescriptive guidance. The assessment allowed for the rationalized of structural protection to the walkway providing the most cost effective solution while maintaining the primary goal of life safety.

The external fire spread assessment was carried out using BR 187: External fire spread: building separation and boundary distances. This assessment allowed for the optimum amount of fire protection to the external walls of the visitor centre in lieu of the more onerous requirements under the prescriptive methods.