The Hill House by Charles Rennie Mackintosh (1902-04) is widely considered a seminal work of early modern architecture. Today, after more than a century of saturating Scottish weather, the house is crumbling from water damage and needing renovation. In 2019, the first stage of works to stabilise the house and rectify its damp walls began in radical fashion with the ’Hill House Box’ by London-based architects Carmody Groarke. Like an oversized architectural raincoat, this roof and chainmesh-walled structure completely encases the house, allowing it to dry out before conservation works can begin. The design also incorporates a series of walkways through the interstitial volume, enabling visitors to observe the old building from new vantage points during its renovation. As such, the enclosure not only forms a protective case, but effectively turns the building - and its conservation - into a museological exhibit.

The architectural interest of the Hill House Box, however, lies in its encounter with Mackintosh’s temporally and stylistically distinct design, and the perverse strategy of placing one building inside another. For this essay, the Hill House and its new box highlight the underexamined architecture of buildings-in-buildings and, in particular, the creation of spaces that are neither interior nor exterior, but both, simultaneously. Drawing upon a diverse array of buildings and texts, this paper will attempt to outline a theoretical framework through which such composite constructions might be better understood. In particular, it will argue that, while there are countless ways that buildings have historically become encased within other buildings, it is within museums and sites of preservation, like the Hill House Box, that these fantastic architectural encounters find their most exciting and emphatic expressions.