The original Allermuir House was built by Robert Rowand Anderson in 1879 and was named after the Pentland Hill that the house overlooks. Several additions had been made to the original asymmetrical Scott Jacobean house, and Anderson himself was responsible for the first, but little documentation exists for the two rendered additions to the rear. 

The proposal demolishes these later outbuildings to the ground floor and replaces them with a contemporary extension, accommodating a new kitchen and dining room. A connection is made to the existing house by forming a secret door through one section of the panelling to the hall, opening up a simple  route from the front door of the house to the extension. An opening is then formed, through the scullery into the extension. The previously complex internal circulation benefits from the straight route and its link with the extension is direct and clear, yet discrete. 

The main volume of the extension pulls away from the building, preserving the integrity of the chimney-breast, and allowing a deep recess to separate the original fabric of the house from the new. This provides high levels of daylight to the new spaces, which is further reflected by the white-rendered side wall of the extension.