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Under one roof

aj building study

Riverhead Infants School at Sevenoaks in Kent, by Architects Design Partnership, is a clearly set out response to the school's brief for an educationally and environmentally responsive building

While Riverhead School was doing well educationally, with good OFSTED reports, its former accommodation needed improvement. Its small Victorian buildings still included outside WCs, and there was a range of 'temporary' classrooms which, following a fire some years ago, housed eight of the nine classes. Fortunately, Kent County Council had a wooded Green Belt site close by, formerly reserved for a bypass scheme, opposite a junior school. Of the £2.6 million project budget including highway works, some £1.5 million came from sale of this old site for housing development.

The governing body of governors and teachers were given project management responsibility for the new school, one of the first groups to be given so much autonomy by the county. The body does possess construction expertise - parent governor Roger Olsen, a services engineer with Arup, and building surveyor Mark Stott, who drafted the brief.

And this expertise was needed, with the tight DFEE space standards and cost limits to be negotiated, plus setting an environmental as well as an educational agenda.

With the county, the governing body organised a competition, using its contacts to find entrants, and giving the architects five weeks to prepare an outline proposal, general feasibility and a fee bid. They saw all five entrants and made a decision on the same day in May 2000. Olsen admits their surprise at how much work the entrants had done. The winner was Architects Design Partnership, beating four others - Kent Property Services (from the county authority itself ), Brookes Stacey Randall, Arup Associates and Barnsley Hewett & Mallinson Architects.

Riverhead School has a straightforward legibility, from the site layout to the building form to the single-storey plan. The rectangular block faces north-west onto the A25.While pulling the building back from this helps with noise, sound protection also comes from space planning. A wall of small-windowed spaces on the front - staff accommodation, library, IT area and assembly hall - protects the classrooms ranged along the back and their associated outdoor spaces.

A Travel Plan was an important part of the planning application. The space in front of the building provides a car park and set-down area for school runs. There was concern that this space would not be big enough, although most pupils live within three-quarters of a mile. A survey three years ago showed that 56 per cent of pupils arrived by car, some 150 vehicles. But the school has tried to encourage walking, notably with the setting up of three 'walking buses'. For these, adults meet children at prearranged stops and walk with them to school. As well as roadside footpaths, there is a main footpath across fields from the east, the direction of the previous school. So far the prognosis is good.When Olsen visited the school at the end of September, he counted only 12 cars.

The building form can be read in part as an environmental response, the arch-section offering a streamlined profile to the prevailing southerly winds, the intended streamlines emphasised by the main structural tube arches which run to the ground.

Some changes have been made to the diagrammatic idea. The grass roof has been cut to sedum to save weight and thus structure cost, the earth-shaping has given way to flat outdoor teaching and recreation space, and the landscape will take some time to match the lush screening illustrated. But the focus on balancing the needs of southerly openness and protection remains. All the class bases - one per structural bay - have fully glazed walls, shaded by parallel tubes (cheaper than louvres). Calculation suggests no internal blinds will be needed, although they could readily be fitted. Outside, canvas sail infill panels in the open arches both provide some shelter and separate one class base's external space from another. The designer took advice from a BRE environmental audit at an early stage.

Approaching the entrance from the road, the building offers a single, striking presence, clearly spelling out that the school is now under one roof. The entrance/reception area is marked in red, outside and in, and then in the wall straight ahead are the doors to the playground, a secure entry route. Windows are set 900mm above the floor, a dimension arrived at by a school exercise measuring the pupils' average eye height.

Housing up to 270 pupils, the school is three-form entry (30 per form), providing for reception classes, Year 1 and Year 2. The most protected area is for reception pupils, on the left of the entrance. These pupils are located closest to the staff offices. The closable class bases, with WCs within, will help contain them.

A set-back in the back wall marks off this separate reception class area. It also draws attention away from the slight dog-leg in the rear building line. Reception class bases are allowed 5m 2more floor space than other years, so with a uniform 7m structural grid, that extra area pushed the rear wall further out here than for the other six class bases.

Internally, class bases are similar - servant spaces one end, a glazed wall the other, between white plastered side walls. Ceilings are perforated acoustic soffits of the profiled metal roof. Floors have a high-build plastic paint finish on screed over underfloor heating.

The class bases feel light and fresh. The furniture from the previous school becomes less noticeable as the clutter of use accumulates.

Air freshness is always an issue in class bases. When it is too cool or windy to open the glazed double doors, there are vents available above door heads in most class bases, and the rooflight opens to improve stack ventilation. The section helps here too, with the ceiling rising towards the rooflight, creating some of the useful ventilation volume provided by the traditional high Victorian schoolroom. Unfortunately, the greater plan depth of the reception class bases reduces the height under the sloping roof for glazed external walls, and the cladding manufacturer was unable to fit louvres into the shallower gap above the doors. There are trickle vents in the frames but some custom-made louvre panels may well be needed in the future.

The 'corridor' down the spine of the building makes circulation clear for small people.

It is in practice a more three-dimensional space than the plan may suggest, with its high arched roof and rooflit 'winter gardens'.

These winter gardens enliven and open up the linear route as well as side-lighting the northern rooms with their smallish, soundlimiting external windows. In one of those Catch 22s of space allocation, the winter gardens count as lightwells, but it was cheaper not to wall them in. They await fundraising by the school to populate them with plants.

There are limitations to this corridor, though. The class bases' servant spaces project into the corridor, but only at normal ceiling height, with potentially dusty space above - a void that may prove tempting for storing materials, pupils' work and other clutter. And at the entrance to the assembly hall, the corridor does feel narrow and under-illuminated. Some rooflights were lost to cost reduction.

Once inside the hall, you are in a relatively light, high volume that projects above the curved roof. It is used for eating packed lunches as well as school activities, and can accommodate all pupils, often not the case in schools today. A neat move has been to set back much of the internal wall and paint it blue to create the sense of a proscenium arch.

This colour is used externally to mark the hall too. Beyond the hall is the IT classroom - the brief looked ahead to computers in class bases too - and the library, including a softer area for storytelling. Not to forget more WCs, never far from thoughts in a primary school, located at either end of the corridor for children using outdoor spaces.

With the school's history of temporary buildings, the governors did consider the potential for expansion but decided to give it low importance in the brief. Internal change is possible, with non-loadbearing partitions.

But generally they felt that three-form entry was as large as they wanted the school to be.

This allowed the designer to develop a contained structure. The designer was also successful in changing the expectations of the brief for a building 'likely to be [in] traditional enveloping materials with pitched roofs'. It has delivered an innovative yet straightforward and friendly learning environment for what is, for many, pupils their first day-to-day experience of a major building. It is a real second home for the school.

Environmental design

The form and layout of the school relate directly to its setting, with the landscape sweeping up to and over the building. All classrooms face south, with floor-to-ceiling glazing overlooking parkland. The north elevation is more solid, acting as a buffer to the busy A25 road.The building footprint is compact and efficient, maximising usable space and minimising external heat loss. The heavily insulated sedum roof acts as a thermal sink while external louvres prevent excessive solar gain.

Local and recycled materials have been used where possible, such as crushed recycled glass rather than sand for bedding paving materials.

External render is water-based and solvent free.

Our design concepts take account of Kent design: a guide to sustainable development, and were tested at an early stage by a BRE audit. This found that our strategy was sound, and suggested refinements were implemented.

A series of 'walking buses'have been established, for which trained adults collect children at a series of stops on fixed routes which converge on the school. Footpaths have been upgraded and road crossings provided: all part of the school's Travel Plan.

The site itself was brownfield, having been used as a road builder's compound, then as a dump. The green roof extends the gently rolling terrain while new trees will screen the road and act as an air filter. The glorious south-facing grounds retain exceptional mature oak trees close to the building. New planting provides a protected wooded environment rich in wildlife, and safe sunlit spaces for outdoor learning and play.

Many aspects of the design relate to the scale, needs and interests of the children. Our attempts to integrate the building with its context, and to minimise its use of energy, convey important messages to the school's pupils in their formative years about a wide range of environmental issues.

Roger FitzGerald, Architects Design Partnership

Structure

The building's strong and natural structural form emerged from the fusion of ideas between architect and engineer, given a real greenfield site and a blank canvas.The skeletal steel tubular bowstring arches, tied with Macalloy bars under the footprint of the building, give clean structural lines.Placed on a grid of 7m, they define the classroom widths. A single line of 'pencil columns'defines the central corridor and props the three-pinned arch to enable the lightweight structure to carry the sedum roof. Slim external posts are used as deflection-limiters at the external face. A Plannjaprofiled decking, exposed internally, forms the structural deck and also acts as a structural diaphragm, negating the need for conventional bracing.

The decking is stitched to the folded plate fabricated eaves beams, and together with a central row of tubular ties on the pencil column lines, carries loads back to the main entrance hall 'goalpost'portal frame, which is expressed as part of the entrance to the building.This, together with braced stud walls to the hall, provides all the structural stability when combined with the natural benefits of the arch.

Early meetings with steelwork fabricators confirmed both the buildability and economics of the chosen structure, and W S Britland eventually won the competitive tender for the steel frame subcontract.

The design team was additionally grateful to Littlehampton Welding for its early input, which aided the success of the project.

Foundations are relatively orthodox with a sand natural stratum.

Shaping of the site was required and the sand was ideal as cut-and-fill material to achieve the flat warehouse-like formation. Pad foundations and the ground slab together with the below-slab ties were all installed prior to steelwork erection and gave the required working base to erect it.

With effective pre-planning, the fabricators adopted the designer's intentions of on-site welding to complete the tubular arches. Erection of the frame was relatively hitch-free. The high quality of detailing and workmanship required was achieved.

Anthony W Ward, Anthony Ward Partnership

Costs

The analysis is based on the tender sum. Costs rounded up or down to the nearest pound

SUBSTRUCTURE FOUNDATIONS/SLABS £71.22/m 2Reinforced concrete bed, damp-proof membrane and insulation; plain and reinforced column and rib bases

SUPERSTRUCTURE FRAME £143.15/m 2Exposed decorated tubular steel arched ribs with tension bars in under-slab ducts, central support columns and reinforced concrete buttresses; steel frame to entrance and assembly halls

ROOF £196.81/m 2 Sedum roof coverings on insulated profiled galvanised metal structural decking with exposed finish to soffit; aluminium eaves fascias; fall-arrest system

ROOFLIGHTS £43.78/m 2 Circular rooflights to classrooms and two large rectangular rooflights to internal garden areas; all remote motor-driven operation

EXTERNAL WALLS £72.83/m 2 Insulated block cavity walls with coloured render finish

WINDOWS & EXTERNAL DOORS £56.75/m 2Double-glazed, aluminium-framed windows and entrance doors, and glazed screens and doors forming south elevation walls to classrooms

INTERNAL WALLS AND PARTITIONS £60.38/m 2 Painted plasterboard metal stud partitions; glazed screens between classrooms; WC cubicles

INTERNAL DOORS £35.49/m 2 Painted flush timber doors generally; laminate classroom doors; servery shutter

INTERNAL FINISHES WALL FINISHES £16.39/m 2 Painted plasterboard linings; laminate panel and ceramic tile splashbacks

FLOOR FINISHES £53.07/m 2 Reinforced screed; poured seamless polyurethane flooring generally; carpet to library; coir entrance mats; painted MDF skirtings

CEILING FINISHES £6.01/m 2 Plasterboard linings to classroom WCs; Gyproc MF gridded ceiling to entrance and assembly halls

FITTINGS AND FURNISHINGS

FURNITURE £12.51/m 2 Classroom pinboards and whiteboards; coat hooks and battens; servery fitments; reception counter; signage

SERVICES SANITARY APPLIANCES £19.69/m

2SERVICES EQUIPMENT £3.36/m 2 Servery appliances

DISPOSAL INSTALLATIONS £7.94/m 2

WATER INSTALLATIONS £31.13/m 2

SPACE HEATING/AIR TREATMENT £67.58/m 2 Gas-fired low pressure hot water under-floor heating;

mechanical ventilation to WCs

ELECTRICAL SERVICES £93.70/m 2 Mains and sub-mains distribution, lighting, emergency lighting and power P

ROTECTIVE INSTALLATIONS £14.46/m 2 Intruder and fire alarms; disabled WC call

COMMUNICATION INSTALLATIONS £6.84/m 2 Telephone/data system cables; TV/FM aerial system BUILDERS'WORK IN CONNECTION £7.11/m 2

EXTERNAL WORKS LANDSCAPING & EXTERNAL DRAINAGE £299.80/m 2 (Including proportion of preliminaries, overheads and profit. ) Extensive site clearance; access roadway and car parking; perimeter paving, footpaths and play areas; extensive soft landscaping with tree, shrub and bulb planting and grassed areas; metal boundary fencing, barriers and guard rails; foul and surface water drainage; external lighting

PRELIMINARIES PRELIMINARIES, £138.70/m 2

OVERHEADS AND PROFIT

WEBLINKS

Kent County Council www. kent. gov. uk

Architects Design Partnership www. adp-architects. co. uk

CM Parker Browne www. cmpb. co. uk

Slender Winter Partnership www. swpltd. co. uk

Rummey Design Associates www. rummey. co. uk

The Buxton Group www. thebuxtongroup. co. uk

Babtie Group www. babtie. com

CREDITS

TENDER DATE 3 April 2001

START ON SITE 9 July 2001

CONTRACT DURATION 51 weeks

GROSS EXTERNAL FLOOR AREA 1,340 m 2

CONTRACT/ PROCUREMENT JCT Local Authorities with Quantities,1998 Edition incorporating CDP Supplement

TOTAL COST £1,954,652

CLIENT The governors of Riverhead School/ Kent County Council

ARCHITECT Architects Design Partnership: Roger FitzGerald, Claire Appleby, Nichola Wood, Alison Golding, Kirsty Burnett

QUANTITY SURVEYOR C M Parker Browne

STRUCTURAL ENGINEER Anthony Ward Partnership

SERVICES ENGINEER Slender Winter Partnership

LANDSCAPE Rummey Design Associates

MAIN CONTRACTOR The Buxton Group

HIGHWAYS CONTRACTOR Babtie Group

SUBCONTRACTORS AND SUPPLIERS Rooflights Rooflight Systems; green roof Erisco Bauder, E J Roberts; render Sto, N B Stonecraft; steelworkW S Britland; metal gate Twickenham Forge; electrical GWE Smith & Son; mechanical Vivathorn; metal decking/ fascias Plannja, T A Colbourne; steel chains for drainage John Howard & Sons; flooring Sports Surfaces; fixed furniture, cubicles Decra Plastics, David Bailey; doors Leaderflush + Shapland, Decra; lighting Lyktan Lighting; windows Kawneer, Dudley;

ironmongery Higrade; sails Spencer Rigging; signage H B Signs; rainwater drainage Alumasc

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