The Boiler House, Within the Kitchen Garden

The Boiler House, located within the kitchen garden, is a Grade II listed building designed to heat former greenhouses, dating from the early to mid-19th century. It is constructed of granite rubble with dressed granite quoins, jambstones, sills, and lintels, while the rear is made of stuccoed brick. The building features a hipped scantle slate roof with clay ridge tiles and hip finials, along with cast iron ogee gutters.

The structure has a four-bay rectangular plan, with the left and right bays slightly projecting at the front. The central two bays are connected to the end bays by wide elliptical brick arched openings through the stone cross walls, and there are stairs in the front corners. In a simple classical style, the building is two storeys high with a symmetrical north front featuring a 1:2:1 bay arrangement. The centre two bays are recessed and include a central doorway with a ledged door and a small paned overlight. Flanking the doorway are original 16-pane hornless sash windows, while above are squat 8-pane horned sashes in their original openings. The left and right stair bays project forward, and the roof slopes slightly lower in these areas.

Each end bay features a half-dome headed brick niche, with a pedestal plinth in each niche supporting a terra cotta eagle. There are doorways at either end that originally led to former greenhouses or potting sheds. The rear displays elliptical arches outlined in the surviving stucco, indicating the positions of former structures, and there is an off-centre round headed doorway towards the right. The interior retains a 19th-century floor and roof structure. This building is a rare example of a purpose-built boiler house and is part of a group of structures associated with Clowance House.