Architect's account MICHAEL BLAIR
Blair Associates Architecture, formerly Blair Eastwick Architecture Halliburton Brown & Root is one of the world's leading consulting engineers, involved in energy services, environmental, civil, and structural engingeering and construction management. In 1995 Blair Eastwick Architecture (now Blair Associates) won a limited competition to design a purpose-built campus for HBR on the 22ha National Power Research and Development site to the north-west of Leatherhead town centre. As HBR works on large and varied projects, the structure and demands of the project team vary, resulting in a large 'churn factor'. The brief therefore demanded that the 28,000m 2of office space should be housed in a series of stand-alone buildings rather than in one monolithic block. The client wanted a 'green' building, which could avoid air-conditioning, while supporting a high density of employees and intensive IT use.
The final masterplan comprises two buildings and a multi-deck car park, arranged around the central building of approximately 13,000m2 gross: an almost medieval arrangement of the citadel, a focal centre and accumulating social support structures, inspired by Louis Kahn's project for the parliamentary buildings in Dacca. The buildings are orientated towards a central entrance which, when the masterplan is completed, will be joined by a covered concourse forming a central reception area. The buildings have predominantly glass facades, widely spread structural column grids, and horizontal roofs.
The central building is on four floors with excellent views from the upper floor. It is arranged on a true north, south, east, west axis and oriented so that views of the National Grid structure can be seen only obliquely. Upper floors are arranged around a central atrium with circulation cores at each corner, comprising an entrance, lift, WCs, stairs, environmental ducts and kitchen. North and south corners are escape routes with IT rooms on alternate floors. To the east, opposite the main core, there are additional WCs, goods lifts and escape cores.
The flanking buildings take full advantage of the north-west and south-west aspects of the site.
The 6000m 2south building has two-storeys, the 9000m 2west building is partly two-storey, but takes advantage of the sloping site to gain two additional floors to the north while maintaining a consistent roof line. Both buildings are organised on a triple right-angle platform. The open-plan office is arranged around primary cores, with sufficient plant and metering capacity for the buildings to be let as autonomous units. The fourth structure, to the north-east of the site, is a terraced multi-level car park which screens some of the National Grid buildings. Plant areas on the roof have been kept to a minimum and have been enclosed to create white roof pavilions. The main plant is located above the cylindrical entrance to the central building. External columns are finished in white aluminium, and white aluminium solar foils have been added to the column grid on the south, south-west and northwest elevations. Solid facade elements such as shear walls in the cores are in Portland stone.
The high thermal mass of the structure acts as a heat sink, cooling at night to the point where it assists to reduce ambient daytime temperatures.
A floor displacement air system relies upon opening windows and opening vents located close to the soffit of the reinforced concrete slab. The underside of the slab is coffered to ensure exposed areas of cooling, and modulate office space. The coffers are located on a 1.5m planning grid, and are connected by two spine beams running the length of the building. Bifurcated columns are located at the centre of the building at 7.5m intervals supporting the central area of the slab through which the external ducts pass to the core.
The soffit of the slab is painted white to reflect uplighting and produce soft diffused light at the working plane. Specially designed light-fittings are located within the ceiling coffers, running parallel to the facade at 3m intervals. The sill height of the office space is generally 0.8m above finished ground level, below is a solid wall containing perimeter heating, data services, power supply and telephones. There is a false floor at 450mm containing IT circulation routes and displacement air ventilation outlets.
Structural engineer's account KIM GRADY
Halliburton Brown & Root Floorplates of 15m widths are supported by columns on a square grid of 7.5m centres.
Perimeter columns are within the cladding zone to allow flexibility in furniture planning. Floors and roofs are of exposed concrete, and the ceiling is of sufficient mass to act as a thermal sink.
Being exposed, construction joints on the soffit must be disguised. A ribbed slab satisfies this requirement, as the coffers formed between ribs can be given shape and provide useful space to house lighting units. The transverse span of the coffers is arranged to aid the cross-flow of air from the ventilation system. Coffers are openended to accommodate mechanical louvres at high level, and perimeter support is in the form of an upstand beam. This arrangement makes for faster withdrawal of formwork for re-use in a flying-shutter arrangement.
Virtually all the concrete structure is exposed, and a family of purpose-made glass-reinforced plastic formwork moulds maintain quality and allow repeat use of the forms.
Bifurcated columns support the central spine beam while maintaining continuity of ducting.
The columns are precast and built in to ensure structural integrity, buildability and a high quality of form and finish.
The fully glazed atrium roof is supported on a system of bow-string rafters formed from tubular steel top chords and Macalloy bar tension rigging members. Cantilever arms support the Planar glazing fixings on a 1.5m grid. The rafters are set on a common skew plan. The significant thermal movement of the roof is accommodated using an arrangement of linear rocker bearings.
Mechanical services design KEITH REID
Appraisal STEPHEN GREENBERG
Head of architecture, DEGW Offices are work places first and foremost. Do they do the business? The big success of HBR's n ew headquarters is the office floorplates: the 15m span supported by sculptural bifurcated columns that resemble concrete wishbones, and permit a return air duct to pass between the bones. The office space is day-lit from both sides with internal blinds and external reflectors. The net effect is to create spaces whose power has not been diminished by the low-grade furniture brought from previous offices.
This is a mixed-mode building with a number of valuable lessons for other architects and their clients. The trick is not to exceed 15m in depth and to have both perimeters facing the outside.
Displacement ventilation is easier to control when it is balanced with night-time fabric cooling and some high-level cross-ventilation, than when one face of the floorplate is open on to an atrium. Air quality is fresher than in recent stack-ventilated atrium buildings I have visited; this may be because there is no recycling and mechanical extract in HBR's building. The same applies to parts which face into the atrium, which is glazed but provides the same high-level crossventilation: there may be a lesson here for designers of mixed-mode in open-atrium buildings.
The daylighting is a great success. While visiting the building on a sunny day, the lighting was switched off and the ambient quality was good. This, I suspect, is a better model than Michael Hopkins' Inland Revenue building where the exposed concrete is not painted white, and blinds are adjustable but permanently down. But at HBR the perforated roller-blinds are already a maintenance problem because they are not interstitial: some are crumpled and there is no BMS override to enable them to be more finely tuned. That said, viewed from the inside, one of the most interesting aspects of this building is the way light is reflected off the blinds, vertical fins and external white-glazed spandrels on to the underside of the large exterior solar gull-wings.
This suggests that there are real opportunities, particularly with low winter sun, to explore the architecture of the brise-soleil and the way it can model light.
When completed, the complex will be classical palatial format with wings. At first sight the plan of the wings might seem generous in perimeter, but it does achieve its ends of preventing space from being relentless and allowing for discrete sublettings if required. The rich elements which are combined in cladding and elevation, come together with greater aplomb on the two-storey building than on the four: the compositional transition from one scale to another is difficult.
But the large building does work well around its central atrium, which is really the heart of the project. While sitting and eating you can see the sky through first-floor windows, though this view is blocked by the unsightly furniture which ignores the space-planning regime, and is spread along the perimeter: a fritted film is needed here to hide all the crud. Once again the environmental strategy of displacement ventilation from the floor of the atrium, with stratification and extract at high level, permits a clear glass planar roof. The restaurant is in the middle of the atrium. The knowledge centre, at one side of the restaurant, has a structural glass flat-roofed extension projecting into the atrium - interesting how quickly an award-winning small job becomes common currency.
In places, in particular the red-painted stairs and suspended gantries inside the entrance drums, the architect has evoked the engineering ethos of the client's business. This was an opportunity to respond to the world of oil-rigs without doing a Richard Rogers, especially as HBR was the structural engineer for the project. But these ideas are not carried through into the interior design. Doors, panelling and interiors are more conventionally corporate.
Many a more celebrated building wouldn't have such a good basic concept for the workspace.
There is a very erudite idea about draining large panels of reconstituted stone cladding, based on a real analysis of how water runs off the surface and how to deal with the big ugly joint - one of the few times an architect has knowingly borrowed from the detailing of Carlo Scarpa without being merely gratuitous. The trouble is there was a building in this detail alone. Perhaps this project has too many good ideas. Walter Gropius is reported to have said to a student arriving at Harvard from Taliesin and presenting a Wrightian first project, 'Nein, too rich for me.'
Cost comment CHRIS BOUND
Davis Langdon & Everest Construction of Hill Park was carried out over a period of 18 months by specialist contractors working under a construction management arrangement.
The development comprised two office buildings, a multi-storey car park accommodating 560 cars and infrastructure/ landscaping work in the 4ha site. Hill Park Court, the four-storey building with an atrium, has a gross internal area of 13,340m 2. The smaller two-storey building, known as Hill Park South, has a gross internal area of 5605m 2.Although initially intended to be serviced using four-pipe fan-coil units, the early decision to adopt a 'mixed-mode' solution necessitated a major reworking of the cost plan. Interestingly, the overall capital cost did not change significantly as the cost savings obtained on mechanical services and suspended ceilings were virtually balanced by the additional cost of fair-faced coffered soffits and motorised windows.
The following costs cover the whole development and represent the actual final accounts. They include the construction manager's staff costs and all the various organisation packages carried out directly for the construction manager. The cost of demolitions and enabling works are excluded, and other normal exclusions such as VAT , professional fees and loose furniture also apply.
SUBSTRUCTURE & SUPERSTRUCTURE PILING £19.00/m2 600mm-diameter reinforced concrete bored piles ranging from 15-18m long to both buildings and multi-storey car park
SUBSTRUCTURE & CONCRETE FRAME £246.77/m2 Reinforced concrete pile caps, ground beams and groundfloor slabs, reinforced concrete frame, troughed upper floors and roof with fairfaced soffits ready for decoration, precast feature columns along centre of each wing, in-situ car park structure including underslab drainage, rainwater goods and waterproofing to top deck
STRUCTURAL STEELWORK £21.80/m2 Steel framing to roof-level plant rooms and to roof overhangs
ROOFING & PLANT ROOM CLADDING £55.32/m2 Inverted roof finish to Hill Park Court comprising single-ply membrane, insulation and paving slabs. Profiled sheeting to Hill Park South, roof overhangs of Hill Park Court and plant rooms of both buildings, insulated sandwich panels and louvres to walls of roof plant rooms, latchway systems, roofs to car-park stair towers
ATRIUM ROOF £31.72/m2 Fabricated circular hollow steel beams with tubular outriggers spanning diagonally across 'L'-shaped atrium; double-glazed Planar units laid sloping and sealed with silicone mastic; special latchway system
WINDOWS AND CLADDING £166.96/m2 Double-glazed window modules with manually opening lights and high-level motorised fanlights controlled by BMS; aluminium cladding to columns and spandrels; curtain walling to drums; soffit cladding and fascia to roof overhangs; aerofoil section brise-soleil; entrance screens with revolving doors
RECONSTRUCTED STONE £34.05/m2 Reconstructed stone cladding to feature areas
INTERNAL GLAZING £21.48/m2 Frameless glazing to perimeter of atrium with high-level motorised fanlights controlled by BMS; frameless glass walls and roof to library and kiosk within base of atrium
INTERNAL FINISHES AND FITTING OUT DRY LINING £30.98/m2 Plasterboard walls to cores; drylining to external columns and solid elevations
OFFICE PARTITIONS £20.43/m2 Plasterboard intermediate walls with frameless glass fronts and doors
CORE FIT-OUT £42.28/m2 Finishes, sanitary appliances and services to WCs, showers, tea rooms, main kitchen, private dining rooms and conference room suite
RAISED ACCESS FLOORS £28.45/m2 450mm-high medium-duty raised access floor to general areas; heavy-duty floor atrium base and reception area to accommodate mobile access equipment, bridging over air ductwork and service pits
GENERAL JOINERY £24.39/m2 Hardwood veneered doors and frames including ironmongery; duct access doors and frames; lacquered MDF panelling to conference suite
METALWORK £23.59/m2 External staircases; plant room access stairs; steel feature staircase to main core of Hill Park Court; steel balustrades with stainless-steel handrails to all other staircases; sundry handrails and other metalwork
SOFT FLOOR FINISHES £19.00/m2 Carpet to general areas; studded rubber flooring to stairs and landing
DECORATIONS £8.81/m2 Emulsion paint to all exposed concrete and plasterboard surfaces; paint to skirtings and duct access doors
INTERNAL BLINDS £4.65/m2 Fabric roller blinds to all windows
SIGNS £2.48/m2 Statutory and corporate signs; entrance signs
SERVICES PLUMBING & MECHANICAL INSTALLATIONS £123.99/m2 Underfloor displacement air system with cooling; perimeter heating; supplementary cooling to conference suite; mechanical ventilation to WCs, tea rooms, showers, etc; heated screed to atrium base; extract canopies to main kitchen
CONTROLS AND BMS £18.16/m2 Control equipment and cabling to mechanical services installations and motorised windows
CATERING EQUIPMENT £7.97/m2 Equipment to main kitchen and atrium servery
ELECTRICAL SERVICES £134.07/m2 HV transformers and switchgear; LV switchgear and distribution boards; lighting with purpose-made luminaires to office areas; general lighting to cores; feature lighting; underfloor mini-busbar distribution with perimeter service pillars housing power, voice and data outlets; fire alarms; power for mechanical services; basket and containment for voice and data cabling
STRUCTURED VOICE AND DATA CABLING £23.07/m2 Category 5 unshielded cabling for voice and data with fibre data and copper voice backbones; patch panels and frames; LJ6 voice and RJ45 data outlets to perimeter service pillars with additional underfloor boxes in selected areas
LIFTS £18.00/m2 Bank of three passenger lifts and one goods lift serving four storeys in Hill Park Court. Two passenger lifts serving two storeys in Hill Park South
SECURITY INSTALLATIONS £11.51/m2 CCTV system with 11 cameras; proximity card access control system; presence detectors and alarm system
EXTERNAL WORKS HARD LANDSCAPING & UNDERGROUND £115.33/m2
SERVICES Recontouring; roads, paving and gravel parking bays; underground drainage and incoming services
SOFT LANDSCAPING £22.43/m2 Topsoil, seeding, turfing and planting to site; external cladding to car park comprising vertical timbers with horizontal stainless-steel wires to support climbing plants
PRELIMINARIES GENERAL BUILDER £50.57/m2
ORGANISATION COSTS £63.73/m2
CONSTRUCTION MANAGER'S STAFF & FEE £59.01/m
Piling 19.00 1.32
Substructure & concrete frame 246.77 17.14
Structural steelwork 21.80 1.51
Roofing & plant room cladding 55.32 3.84
Atrium roof 31.72 2.20
Windows & cladding 166.96 11.59
Reconstructed stone 34.05 2.36
Internal glazing 21.48 1.49
Drylining 30.98 2.15
Office partitions 20.43 1.42
Core fit-out 42.28 2.94
Raised access floors 28.45 1.98
General joinery 24.39 1.69
Metalwork 23.59 1.64
Soft floor finishes 19.00 1.32
Decorations 8.81 0.61
Internal blinds 4.65 0.32
Signs 2.48 0.17
Plumbing & mechanical installations 123.99 8.61
Controls & BMS 18.16 1.26
Catering equipment 7.97 0.55
Electrical services 134.07 9.31
Structure voice & data cabling 23.07 1.60
Lifts 18.00 1.25
Security installations 11.51 0.80
Hard landscaping & 115.33 8.01
underground services Soft landscaping 22.43 1.56
Subtotal 1276.69 88.66
GENERAL BUILDER 50.57 3.51
ORGANISATION COSTS 53.73 3.73
CM'S STAFF AND FEE 59.01 4.10
Total 1440.00 100.00
CLIENT Haliburton Brown & Root
ARCHITECT Blair Associates Architecture, formerly Blair Eastwick: Michael Blair, partner in charge; Christopher Firth, associate; Colin Eastwick; Adam Baines, Martyn Pritchard, David Wrigglesworth, Doug Reid, John George
STRUCTURAL ENGINEER AND M&E ENGINEER Brown & Root Structures
QUANTITY SURVEYOR Davis Langdon & Everest
CONSTRUCTION TEAM Brown & Root Projects
SUBCONTRACTORS & SUPPLIERS atrium roof Portal, external cladding package for windows, brise-soleil Witte (UK), reconstructed stone package The Marble Mosaic Co, internal glazing and atrium wall package Optima, flooring and carpets A1 Flooring and Milleken, carpeting Axiom, general joinery & door packages Kilby & Gayford, electrical works package N G Bailey, specialist-designed light fittings Creed Lighting, purpose-made radiators Hudevad Britain, reinforced concrete frame P C Harrington, metalwork Glazards