A roof with a series of extended eaves details
The main entrance/reception space of the medical centre at Arbroath is a double-height entrance atrium with a structure of exposed cylindrical steel columns and a braced steel roof with a sealed built-up roof system covered with standingseam aluminium sheet. Clinical and administrative spaces are enclosed in a timber-frame structure clad either with render or t&g Douglas fir boards. The gang-nailed timber truss roofs, covered with the same built-up roof system, rise gently (at an 8 ° pitch) to just below the atrium clerestory.
Apart from a parapet wall (see Detail A), which adjoins a first-floor roof terrace, the lower and upper roofs extend at the eaves to protect the walls below; the overhang and gutter are detailed to give a consistent edge on all sides of the building.
The sealed built-up roofing system - integral standingseam aluminium roof covering, mineral-fibre insulation and inner profiled steel liner - extends at the eaves, supported on T-shaped tapering steel fins at 900mm centres that are bolted back to the main roof structure. The overhang terminates in a 200 x 100mm aluminium channel, which defines the roof edge. The gutter is set behind the channel and drains into swan-neck downpipes. The eaves soffit is clad with t&g untreated Douglas fir boards on battens fixed to the underside of the fin. An aluminium angle, with a flashing and projecting drip fixed to it, runs just below each overhang to direct rainwater away from the wall below. The angle provides a consistent detail that accommodates various conditions below it, such as a pitched roof (Detail C), timber cladding (Detail B) or an atrium window (Detail D).