CLEVER TRICKS WITH BRICKS

Brickworks
This bold, imaginative, fully sustainable building on a disused brickworks both embraces its past and welcomes the future

Words Hugh Pearman | Photos Hufton + Crow

You don’t know Stewartby? You should. This place – the very definition of post-industrial – was the home of London Brick, mass-producer of your basic self-firing fletton from the local claypits which dot the landscape round about. Just outside Bedford, it was once a forest of smoking chimneys. The 57ha site closed in February 2008, having fallen foul of strict new pollution controls.

Outside the factory gates (‘factory’ here means a sequence of low brick kilns topped with tall, narrow chimney stacks, and associated industrial buildings) London Brick, later part of the Hanson group, built an ultra low-density workers’ village arranged on garden-suburb principles and made, naturally enough, out of the local brick. Built between the 1920s and 1950s, complete with school, churches, shops, swimming bath and social club, it was named in 1935 after Sir Malcolm Stewart, chairman of London Brick, who had conceived it. It is interesting – but too low and spread out to work convincingly as an urban piece.

So what to do with the brickworks site? Next door, another former claypit has been used for landfill but is now full and being landscaped. But here, Hanson has turned developer. There is a masterplan by Studio REAL (formerly Roger Evans Associates) to build a higher-density residential and mixed-use district over the old brickworks on a grid pattern. Four remaining chimneys and two kilns have been listed, though the Evans plan would remove them in favour of a symbolic chimney-like illuminated landmark. Cabe tartly remarked: ‘We find it… perverse to propose the replacement of a real chimney with a symbolic one’, and called for a design code for the development. One to watch.

While the negotiations go on over that, one project has already been built. This is a large, exemplary, properly sustainable new headquarters, just completed at one edge of the industrial site. It was designed and built by TP Bennett to be the new group HQ for the UK operations of Hanson. Designed as not just an admin building but also a showpiece for Hanson’s products, it is thoroughly bespoke. But just before completion the firm decided not to move in, but to market the building instead. So it stands, complete but for loose furniture, waiting for a tenant.

Sophisticated narrative
The project is described as ‘a narrative on how brick can be used in a variety of sophisticated ways reflecting its unique characteristics: as non-load bearing cladding, load bearing walls and as structural frame’. The building, with its two angled wings of offices (and communal facilities like a gym and crèche on the ground floor) plugged into the main social showroom space takes its form from the shape of the site. That site is extraordinary –a patch of partial woodland overlooking a large lake (a flooded former clay pit) beside a smaller stretch of water. As befits the company that commissioned it, it is designed not to turn its back on the desolation of the brickworks site, but to embrace it. It will be a key part of the new community when built.

This 7,000m2, BREEAM-excellent building, contract value £16m, is almost wholly naturally ventilated and has its heat supplied by ground source heat pumps beneath a permeable-surface car park, and heat exchangers in the smaller lake. Together with its high thermal mass, including exposed concrete ceilings, these measures make it a very low-carbon, low-cost HQ for whoever takes it on – although one with an unusually large, triple-height entrance atrium, the area envisaged as its products showcase. The massive freestanding radiators in the building – displayed with pride – are the necessary result of using relatively low-temperature water gained from the heat pumps.

But the building itself is also a showcase. As you would expect, there is some innovative use of both brick and concrete here (it’s a pleasing historical coincidence that the original Sir Thomas Penberthy Bennett, who founded the practice in 1921, did public service as ‘Controller of Bricks’ during the Second World War).

Sight and shade
The 14m tall, slender full-height brick columns to the curving frontage are made in loadbearing pier bond, post-tensioned with steel cables. The aspect of this colonnade means the flanks of the piers act as giant vertical louvres to shade the building – while occupants see out clearly past the narrow ends of the piers. There is some slender steel bracing between the columns, and cross-bracing in the two end bays, but the piers are otherwise freestanding between floor and the rather fine in-situ concrete roof, with its asymmetric integral beams. Another concrete tour de force is the freestanding main staircase, mixing in-situ structure and precast elements. This provides a visual focus to the atrium and a hinge between the two accommodation wings.

The second clever brick trick is to be found in the perforated service cores, lighting escape stairs. These were inspired by the loose stacks of bricks the architects found on early site visits, where apertures are left throughout the stacks for even firing in the kilns. TP Bennett director Mark Stewart and associate director Emiliano Acciarito, working under project director Doug Smith and with project architect Venky Kamat, discovered that solid clear acrylic blocks have such similar compressive properties to brick that they can be regarded structurally as identical, and so can be used instead of more conventional glazing to bring light through an otherwise solid brick wall.

Superior light
The light transmission of acrylic is also far superior to glass of equivalent thickness. The acrylic blocks are arranged in a precisely-calculated staggered pattern through the brickwork, fading away on the flank walls of the stair towers, to give the effect of randomness. Thus distributed they provide a surprisingly large amount of daylight to the stairs, and of course glow enticingly at night. Special thinner, longer bricks are used for most of the building, but are conventionally proportioned in the piers – because the structural properties of the standard product were better known.

It’s no surprise that the team building Tate Modern’s planned extension – another building with a perforated brick skin – has been to inspect Hanson’s Stewartby building as a precedent. In a way it’s a shame that an HQ displaying this level of innovation and good practice is tucked away on a former industrial site, close to a now-full landfill site in another claypit, in a part of the country where few, for now, will venture – because this building deserves to be seen and used. When landscaping works are complete and the brickworks site becomes New Stewartby, it may attract more of the attention it deserves. Hanson has done good work here. In the meantime, congratulations to the TP Bennett team for demonstrating how a younger generation of architects can reinvigorate both a venerable practice, and traditional masonry construction.