Cemex House, formerly RMC House

Cemex House, formerly RMC House, is a corporate headquarters complex designed from 1986 and built in 1988 to 1989 by Edward Cullinan Architects. The structural engineers were YRM Anthony Hunt Associates, the services engineers Max Fordham Associates, and the landscape architects Derek Lovejoy Partnership.

The building has a reinforced concrete frame, cast in situ from RMC concrete. Internally the concrete is fair-faced and painted white; externally it is clad with white vitreous enamel fascias. The cylindrical columns are of precast concrete and incorporate rebates for internal partitions. They are positioned on a 6 by 6 metre structural grid. Much of the external detailing, including columns, Vierendeel trusses (ladder-like frames without diagonal members), rainwater goods, stairs, handrails, seating and ventilation shafts, is of white-painted steel. The double-glazed windows have white powder-coated aluminium frames.

The roof construction is built up from the concrete roof slab with layers of polystyrene insulation, asphalt, topsoil and gravel incorporating drainage and irrigation systems. The roof garden additionally incorporates precast concrete, pebbles, paving slabs, brick retaining walls, glass-reinforced plastic planting boxes, steel and oak seating, and glass block rooflights. The outer walls of the complex, and the elements adjoining Eastley End House, Meadlake House and the Grange, are faced in handmade brick, reflecting the prominence of this material in Thorpe. A variety of materials and planting are employed in the courtyard surfaces and the surrounding hard and soft landscaping.

RMC House is an extensive and continuous complex of low-rise buildings and landscaped spaces. The overall layout is informal and asymmetrical, yet incorporates symmetrical and formal elements. Axial planning and long views play a role in orientation and establish visual connections between constituent parts. The complex is planned around three retained buildings. Eastley End House to the north became the directors' suite and boardroom. The trainee accommodation was originally based in Meadlake House to the west, later converted to the staff restaurant with offices above. Meadlake House, the former stable block, is a two-storey, nine-bay structure of red brick and tile. Staff training functions were accommodated in the Grange, a villa of about 1890. This is a two-storeyed building in the idiom of Richard Norman Shaw, combining red brick, tile hanging on the upper floor and half-timbered gables. Its plan is informal and includes an annexe to the north.

The buildings of 1988 to 1989 are largely single-storey with a continuous roof garden, with landscaping by the Derek Lovejoy Partnership. Two-storey or higher elements of the complex read as pavilions in a formal garden. The office accommodation is arranged into a series of linear spines, disposed around three landscaped courtyards. Meadlake Court adjoins and is aligned with Meadlake House; the opposite end has tapering sides, reflecting an existing boundary. Eastley End Court is symmetrical about its axis with Eastley End House and the circular entrance court to the south. The intervening Fern Court is a narrow space which lights two strips of offices. A central axial route connects the brick additions to Eastley End House with the main office spine and amenity and reception areas to the south. A series of external stairs provides an external route between the courts and roof gardens. Another cross axis links the main entrance, reception area, former swimming pool (now floored over) and access to the lake inlet. A route to the Grange peels off to the south.

The various parts of the complex, and the architectural aesthetic of the whole, are articulated through a palette of contrasting materials, colours and textures. This comprises the white, reflective and smooth surfaces of steel and glass defining the courtyard walls and the edges of the roof garden; the solid, orange-red brick walls of the outward-facing walls, boundary walls and extensions to retained buildings; and the verdant landscaping of the courts and roof gardens. The integral landscaping was intended by the architects to read as a continuous formal garden scheme when overlooked from Eastley End House and surrounding areas such as St Anne's Hill. Notwithstanding, the planned vistas and ease of circulation between the courtyards and roofs is consistent with a multi-level composition.

The courtyard elevations are light, intricate and layered. Structural bays are defined by concrete columns with vitreous enamel casing. The intervening full-height glazing units combine wide sliding doors with narrow casement windows. The cantilevered planting boxes of the roof garden form a broad overhanging fascia, helping to shade the offices below. They are overlain by Vierendeel trusses, spanning two bays and bearing onto slender tubular steel stanchions with jowled heads and tall concrete bases. External stairs ascend from each courtyard to the adjacent roof garden. These are described by Edward Cullinan Architects as 'mounting block stairs': a steel open stair with balustrade and wooden handrail, descending to a stepped, tiled base with a curved end. Variants include two diagonal flights converging at the stairhead in Meadlake Court and a double return stair, with diagonal flights converging at a half landing in Eastley End Court.

Each courtyard has a different landscape treatment although consistent details can be identified. A tiled margin incorporating a drainage channel runs alongside the buildings. Beyond lies a broad gravel footpath (gravel being a key element of RMC's operations), shrubs and herbaceous borders, and a central lawn. Eastley End Court incorporates a formal pool edged with York stone paving. Meadlake Court features a symmetrical design of borders, gravel beds and a raised circular pool which responds to the geometry of the surrounding buildings. To the south is a mature walnut tree. The narrow Fern Court is surfaced with cream tiles to reflect light into the offices, and incorporates fern beds and a grey granite-lined water rill, which leads from a bubble fountain to a diamond pool which frames the staircase.

A formal garden of around 4,500 square metres in area occupies the entirety of the flat-roofed, single-storey buildings. Circulation is around the perimeter, defined by overhanging rectangular planters for clipped yew hedges and holly topiary standards in cylindrical planters. The hedges conceal safety handrails and an irrigation system. Built-in seating and white metal handrails indicate the corners of the courtyards. The perimeters are detailed with a white vitreous enamel fascia to the parapet, a pebble margin and concrete paving slabs. The lawns are bordered with granite edging and brick coping defines raised beds. The roof garden is mainly laid to lawn with hardy borders of juniper, cotoneaster and pyracantha to create a sheltered microclimate. A linear strip of 'Luxcrete' glass blocks lights the central office spine below.

The roof garden incorporates a series of follies, gazebos and pavilions. The roof-mounted air handling units are masked by large pergolas covered with wisteria vines. The metal extract vents take the form of giant chess pieces, painted white or red, in a reference to Lewis Carroll's 'Through the Looking-Glass'. To the south, splayed steps with broad walls lead to a lakeside belvedere. This is diamond in plan with a tiled chessboard pattern. Its gabled gazebo is Edward Cullinan Architects' homage to Joldwynds, Philip Webb's long-demolished house in Surrey. The diverging walls are a trick of perspective: when viewed from below they appear parallel, exaggerating the apparent distance of the belvedere. At the centre of the two principal axes lies a two-storey entrance pavilion, dubbed by its designers the 'Villa Rotunda' after the Palladian villa of that name. This originally contained the executive dining rooms and is now offices. Its upper floor rises above the roof garden with four double-height spaces flanking a cruciform 'crossing'. A continuous ribbon window separates its red brick walls and a virtually flat roof with broad eaves.

The design of extensions to the retained buildings acknowledges their individual architectural idioms. To the west of Eastley End House, a bow-fronted addition originally housed the directors' dining room. Of red brick in a Georgian idiom, it features six-over-six sash windows with gauged brick voussoirs and a dentilled and panelled parapet. A linking section with multi-paned French windows and a veranda leads to Eastley End House. Meadlake House is adjoined by brick and tile cross wings, which complete a U-shaped plan. Dovecote-like square corner towers and square end pavilions with tall dormers are connected by a link block whose pitched roof is lifted clear of high brick walls on a slender steel frame and ribbon window.

The outer edges of the complex are treated as 'inhabited walls', taking their cue from the historic boundary walls of Eastley End House. They are of red brick with a dentilled parapet, small square windows, and rainwater goods cast with the inscription 'RMC 1990'. To the west, the boundary walls include a steel ramp and walkway bridge over the lake inlet, the latter partially concealed by brick arches. The curvilinear external walls to the east recall traditional 'crinkle crankle' boundary walls. The circular entrance court incorporates a central fountain and curved and pierced screen walls.

The workspaces were originally planned with cellular offices at the perimeters at the client's request. Administrative staff were located along an open-plan spine which doubled as a circulation route. The offices were converted to entirely open-plan spaces in the early 21st century. The work spaces incorporate fair-faced, white-painted concrete columns, beams and ceilings, and carpeted raised-access floors. The fully-glazed exterior walls provide natural lighting, supplemented by fluorescent lighting. The deepest parts receive top light from glass blocks set into the roof, now concealed by translucent panels.

The reception hall originally flanked four double-height spaces: pairs of squash courts and staff dining rooms. The semi-open swimming pool and kitchen and storerooms lay beyond. The reception and amenity areas were remodelled in 2001 with the relocation of the staff restaurant, the flooring over of the swimming pool, and the infilling of a loading bay to give additional open-plan workspace. The squash courts were converted into meeting rooms. Surviving original elements of the reception hall include the grey and black granite floor and the exposed columns, beams and ceiling. The elaborate ceiling to the former swimming pool also survives; it rises to an 8.5 metre diamond waffle slab, above which is a smaller, orthogonal grid of glass rooflights.

The structure and services of the building employ passive cooling techniques to achieve a 'thermal flywheel' effect without the need for air conditioning. The high thermal mass of the roof build-up flattens daily temperature fluctuations, absorbing daytime heat while the exposed concrete soffit radiates cool thermal storage from the previous night. The concrete floor slab also acts as a cooling element for incoming air circulated by an underfloor mechanical ventilation system. The full-height glazing units maximise daylight penetration to reduce the need for supplementary artificial lighting, while internal and external solar shading minimises solar heat gain. Openable glazing units, intended to be controlled by occupants, induce cross ventilation to the work spaces. Ground water supplied by a borehole is used to cool the air in the reception areas and to irrigate the gardens.