Richard MacCormac describes the library plan as 'two arcs, split apart to contain the rectangular archive'. The outer walls - the arcs - are of white Lignacite blockwork with dark-green precast string courses. The two 'slots' between the arcs are fully glazed: one, lighting the reading room, faces west towards the sea; the other, facing east, contains the main entrance. It is approached by a raised causeway which leads to a porch, in appearance a solid metal cube with bronze doors; frameless glazing surrounds the porch and gives glimpses of the archive within. The porch leads to a foyer with a glass and slate floor.
The structure of the building comprises hollow-block piers infilled with reinforced concrete. These are set in the inner leaf of blockwork and support a roof structure of paired timber beams.
The glass slot at the entrance is recessed 1.5m from the face of the curved walls. The edges and jambs of the recess are lined with dark-green precast slabs. The upper levels of the slot are glazed with a Schuco curtain- wall system; the lower levels around the porch are of 13.4mm frameless glass laminated with polycarbonate for security and incorporating a uv filter to protect the archive. The glass is fixed in aluminium glazing channels set in the walls of the porch. The edges are sealed with clear silicone.
The raised concrete causeway is paved and edged with precast units. The porch has a structure of 70 x 70mm shs portal frames with an additional 102 x 51mm rsc welded to the central portal. It is clad with aluminium panels on timber framing and lined on the inside with18mm oak-faced mdf panels banded with horizontal brass channels. The two sets of paired doors are clad with bronze on a timber frame.