Some 70 km south of Hanover, a branch line runs west from the railway station at Northeim through farmland dotted with woods. The land becomes hillier, the woods more extensive and, suddenly, the River Weser appears, whose distant outlet is on the German north coast.
Hereabouts, the Weser skirts the small town of Lauenf÷rde, headquarters of furniture manufacturer Tecta, whose factory is part of an industrial estate but has a broad meadow stretching beside it. A few kilometres upstream, near Baroque Bad Karlshafen, the river runs beneath a thickly wooded slope where Tecta's owner, Axel Bruchhauser, has his home.
Bruchhauser is an unusual man, a true patron of architecture. Since 1984, he has commissioned a series of additions and alterations to both his factory and his house, for which the architect has been the same throughout - Alison and Peter Smithson, with Peter Smithson continuing the work after his wife's death in 1993.
At the heart of these interventions is a wish to connect the buildings more intimately, more directly, with their contrasting landscapes - the meadow and courtyard of the Tecta factory, and the wooded slopes of the Bad Karlshafen house, the Hexenhaus.
The phrase that both Smithson and Bruchhauser use to describe this 17-year process is 'step-by-step'. 'It has been like working on a big estate, where the owner looks at the accounts and says, 'This year hasn't been too bad, let's do so-and-so, '' says Smithson. 'All the changes are initiated by Axel. They all stem from a problem he has identified, or an observation he has made.'
There are similarities here to the Smithsons' strategy at Bath University, which they outlined in the AJ (30.11.83). The arts building they had just completed was described as 'a new piece woven onto the edge of an existing matà the first of a series of tassels that are going to be needed to make that mat's terminating fringe.'
Plans in that same issue for the arts barn at Bath included 14 component buildings, which could be constructed in any order as funds were found.
The difference, though, is that all those component parts were envisaged in advance and placed on the plan. This German work has proceeded more speculatively, without a final vision for either the factory or the house. But, both at Tecta and the Hexenhaus, the result is not just a series of pragmatic additions - it is a gradual transformation.
Into the woods The Smithsons met Bruchhauser in the early 1980s through their Team X colleague Stefan Wewerka, who was then a consultant to Tecta. Bruchhauser wanted to explore the possibility of manufacturing some of the Smithsons' furniture - he particularly liked the 1954 Trundling Turk chair - but their dialogue took on another dimension, and before long, led to the first intervention, which was at Bruchhauser's home.
This part of Germany is Brothers Grimm fairytale territory, and Hexenhaus means 'Witch's House'. For Alison Smithson it was 'a Hansel and Gretel house'. Two-storeyed, with a quite steeply pitched tiled roof, it was built of local sandstone and timber just after the Second World War by a former sea captain, and Bruchhauser acquired it some 20 years ago for himself and his cat, Karlchen.
It sits towards the end of a narrowing cul-de-sac at the fringes of Bad Karlshafen, with tall trees gathered around it and paths into the woods behind. There are oak trees here that are 400 years old, while the beeches have stood for a century or more. Photographs of the house before the Smithsons' work began show an introverted property which gives little away.
'I told Alison I needed a new door, ' says Bruchhauser, but in discussion they agreed that what he really wanted was enhanced contact with the immediate landscape, from which the existing house kept him at a distance - 'a place where I could just enjoy the views or sit when the rain is coming.'
So the eventual outcome of his request was a highly deliberated new porch at the south-western corner of the house. It is built of glass and Oregon Pine, a wood suggested by the local carpenter. 'We have had the same master carpenter throughout, and master carpenter means something in Germany, ' says Smithson. 'He has become accustomed to reading our drawings and the quality of his work is staggering.'
'The porch [is] an exemplar of a method by which a small physical change - a layering-over of air adhered to an existing fabric - can bring about a delicate tuning of the relationship of persons with place, ' wrote Alison Smithson in a commentary in the Gustavo Gili volume on their work (1997).
Integral to this addition is a device which Peter Smithson explains in an essay called 'The Lattice Idea', published in ILAUD 19992000, the year book of Giancarlo De Carlo's International Laboratory of Architecture and Urban Design.
Citing the completed Garden Building at St Hilda's College, Oxford (1967-70), and the studies for the Lucas Headquarters competition (1973-74), as early explorations of this idea, he describes the way that a lattice screen over a window or door-opening shapes our perception: 'It affects both our looking-in and looking-out. We are conscious of seeing segments, segments which isolate objects or collections of objects, so we see them strongly. To perform in this way, the lattice bars have to have a certain thickness, which has the effect of isolating and intensifying the fragments seen through the latticeà The thickness of the lattice bars affects what is seen, much in the same way as the frame affects the sense of space in a picture.'
The lattice bars of the porch, which are just under 7cm wide, do not subdivide the glazing into a simple pattern of, say, lozenges or oblongs; nor are they identical.
They rise in an irregular step-like fashion from one edge of the frame to another, looking rather like the branches of the trees beyond - a deliberate allusion: 'The branches that move and the branches that don't, ' said Alison Smithson.
As described in the ILAUD essay, the unorthodox frames that these bars impose on the world outside do focus your attention in unexpected ways, but there are further factors to take into account. The porch reuses separately the French windows that previously gave access from the house to its grounds, and the tight grid of their glazing bars creates a very different outlook. But also incorporated, by contrast, is an uninterrupted, full-height vertical pane of glass, which frames the landscape in its own distinct way.
The perceptual possibilities are diverse.
One repositioned half of the old French windows opens onto steps leading down to a grassy terrace, a transition that is made eloquent by the choice of materials. From the travertine floor of the interior, you step first onto slatted timber, then - as the route bifurcates - onto a block of concrete, and after that roughly-shaped stone, before you reach the grass. The boundary between 'culture' and 'nature' is not abrupt, but a matter of degrees, both visual and tactile.
'With this porch, Alison established the aesthetic for our alterations, a vocabulary which I have followed, ' says Smithson. The porch has since been extended in both directions and is now an approximate L-shape in plan. But it is not just an orthogonal projection from the house: the outer edge of both the original and the additions is faceted, and each change of angle realigns you to the world outside as it redirects your view.
There is a built-in seat at one end, a couple of chairs, and other bits and pieces, including an intricate cabinet by Alison Smithson that hangs on the stonework of the former outside wall (still with evidence of the creepers that adhered to it): this enlarged porch is clearly lived-in, and would seem to be the 'calm cell in nature' that its designers intended.
From outside, you glimpse the stonework through the glass: 'The building has been gradually encrusted, ' says Smithson. In 1998, for instance, he added a porch at the entrance to the Hexenhaus, faceted in the same way as the first but with slightly wider lattice bars in a different pattern - diagonal 'branches' sprouting from an off-centre 'trunk'.
Another, earlier encrustation came with a new window on the south side of the house, now almost adjacent to the extended porch.
The original was placed too high to allow any view of the River Weser at the bottom of the hill. Now, with that window removed and the wall cut away to floor level, you step down into a glass-floored bay-window, set at an angle to accommodate a human-sized seat to one side, and a more elevated catsized perch to the other. Bruchhauser's cat is important to him and the Smithsons acknowledged that from the beginning.
Smithson refers to this addition in another ILAUD essay, 'Being at Home', published in the 1997-98 yearbook. 'Like the porch, one is not conscious of it as a baywindow - rather there is a further space outside the wall, another layeringà consequent simply of the side returns being beyond the sight-lines seen from inside.'
These glazed encrustations are one way in which the house has progressively embraced its surroundings, but there have been others - among them, what Smithson refers to as the 'Hexenhaus holes'. Various excisions in internal and external walls, and both the ground and first floor ceilings, have made visual links between inside and out, in many different directions.
A prime example greets you on entering the house: a semicircular cut through the kitchen wall into the living room, its straight edge at the same angle as the nearby staircase. Beyond this opening, the space is distinctly layered, with a sliding latticed door between the living-room and the porch; then the lattices of the porch configure the backdrop of trees.
What you see is a succession of frames, each overlaid on the next, and the further your eye penetrates, the more complex the sensation becomes.
For the workroom on the south side of the first floor, Smithson has designed a broad new window, divided at varying intervals by three diagonal bars of different length; it gives Bruchhauser a panoramic view when he sits at his desk. A similar lower window in the adjacent bedroom illuminates the floor: 'Perhaps the floor then becomes a place of use, as in one's student days, ' says Smithson.
But, cued by the position of the fachwerk (half-timbering) of German tradition, the cuts on the first floor are mainly triangular:
from the workroom desk, for example, Bruchhauser can look through the inner and outer walls of the intervening bathroom, towards a segment of foliage or sky.
The real surprise here, however, is to find that the low ceiling now suddenly opens up in the shape of a lopsided cone, lifting the eye toward a skylight through which the overhead branches appear. 'They've given me a cathedral dome, ' says Bruchhauser. A smaller equivalent is situated directly above the washbasin in his bathroom.
Back on the ground floor, sitting in the Smithsons' Popova chair from which he watches television, Bruchhauser explains how these encrustations and 'holes' have radically changed his experience as occupant. Turning through 360infinity, inclining his head at times, he indicates some 10 separate vistas from inside to out, as new glazed openings onto nature alternate with the solid original wall.
'The Smithsons have understood my needs exactly, ' says Bruchhauser. 'I don't want the exposure of the Farnsworth House.
I want to see out like this, but I need a sense of protection as well.'
For his part, Smithson reiterates that the changes are all initiated by Bruchhauser.
'We've had the role that Rietveld had with Mrs Schr÷der-Schrõder - we've been the vehicle for realising Axel's wishes. But she was planning in advance, imagining how she would want to live - her decisions were intellectual. Axel, on the other hand, has come to his conclusions through living somewhere, day after day. His decisions are corporeal.'
Over the years, those decisions have borne on the surroundings of the Hexenhaus as well as the building itself. By ancillary and freestanding structures, it has reached out increasingly into its hillside site.
These additions have all been integrated with the existing system of pathways and terraces - paths which, perhaps because their stones are often so lichenous, look longer-established than they actually are.
To the west of the house, a narrow bridge leads from the first floor to a small look-out tower, which in turn connects by a further bridge to a terrace at the rear. On a broader terrace to the east, catching the early evening sun in summer, stands a tea house, its roof thatched with reeds around a central skylight.
The piÞce de rÚsistance, however, is reached from a door that opens directly out of Bruchauser's bathroom. Turn left and a bridge leads you to the slope behind the house. Turn right and another bridge climbs up to the Hexenbesenraum - the Witch's Broom Room.
This is what Bruchhauser calls his 'holiday home': a lofty, tree-surrounded pavilion on stilts - nine 11m oak legs, reinforced with steel. From the roadway, it is blank and unrevealing. 'I show you my cold shoulder, ' he says. But on the north and west are fullheight windows, the pavilion's roof is partly glazed and, crucially, its floor is all of glass. It is like a huge lantern when illuminated at night.
Inside it is comfortably appointed: a broad couch to one side, a bench-seat opposite, an electric fire. The sophistication of its carpentry, coping with complex joints and an absence of right angles, bears out Smithson's comment on German craftsmanship.
As you sit there with a breeze outside, the pavilion sways slightly - a visceral reminder that you are up among the trees.
Ten or more people can be entertained in the Hexenbesenraum, but for Bruchhauser it is primarily a place of retreat, an aerial observatory.
In winter he can lie back on the couch and look up at the stars. As tree-cover returns, he can study a single branch.When he gazes down through the transparent floor, he sees the glazed segments of the roof reflected: they look like mirrors suspended midway between the pavilion and the earth.
The leaves that are overhead in reality, in reflection almost merge with the foliage on the ground. One glance at Bruchhauser's bookshelves, with their volumes on El Lissitzky, Mondrian and the like, suggest how much he must enjoy such optical and spatial ambiguities.
'It is fantastic during stormy weather, ' says Bruchhauser. 'The rain, the snow, comes directly at your face. It is like a theatre. It's so dramatic.'
'You cannot imagine what happens in that room until you experience it, ' he adds.
'If I am to survive as a modern businessman, I need a place like this - a place where I can recharge myself, away from the busy world.
The Smithsons recognised that - it is the most wonderful gift from them. To take such serious care for one person - for his soul - is unbelievable.'
Into the meadow But while thinking of what might enhance his own life, Bruchhauser has also considered his employees at Tecta and, in tandem with the work at the Hexenhaus, the Smithsons have made many improvements there.
The factory, dating from the early 1960s, was designed by its architect-proprietor Hans Konnecke, using rendered concrete block and timber. 'It was built in a very economical way - built in a poor Germany, ' says Smithson. 'Everything was done in a minimum way and has mostly lasted very well. Architects there in the 60s were beginning again. It feels a bit like the Bauhaus.'
By the 1980s, though, some features seemed a little too basic. The Smithsons have installed new WCs, for instance, with the same costly materials and fixtures as in Bruchhauser's bathroom at home, and a screened view of the courtyard outside.
But what distinguishes their interventions is the integration of the workers' welfare with a strategy for the building in its landscape - once more, 'a tuning of the relationship of persons with place'.
In another ILAUD essay called 'Empooling', published in the 1996-97 yearbook, Smithson describes the guiding concept at Tecta with an evocative analogy: 'When there is a sandy beach with rocks standingup from it, as the tide recedes, small pools are left at certain places where the rocks cluster. Similarly, the formation of buildings can carry with it an empooling of the space between and, as with the rock pools, what is within that space-between seems extraordinarily vivid.'
This, he wrote, marked a shift of emphasis on their part as architects - thinking less of the building as an object than of its 'special shaping of the territory'. At Tecta, three areas for that shaping, that 'empooling', were identified: its entrance, its garden courtyard, and the meadow alongside.
The entrance to the single-storey factory is right beside the road leading into Lauenf÷rde's industrial estate, and what the visitor sees first, perched at one corner of the building, is an oversized replica of Mart Stam's pioneering cantilever chair of 1927: an apt sign for Tecta, as classic Modern steel-tube furniture is central to its output.
At the same corner, a wedge of established mixed planting supplies a boundary to this forecourt, while two new raised paths in bianco sardo granite converge towards the otherwise discreet entrance door. A third path, just protruding onto the block paving of this area, heads off at an angle across the grass to a steel-and-glass pavilion by Wewerka, directing your attention to the larger site in which the factory stands, but not raising doubts about where you should go.
This ensemble encourages you to pause for a moment to survey the scene, especially given one other addition - the polished stainless-steel fascia which the Smithsons have overlain on the existing black one. This forms a continuous ribbon around the factory, and its blurred reflections - capturing only parts of things, man-made and natural, and so turning them into semi-abstractions - are an unpredictable visual delight.
But the sense of 'empooling' is much stronger in the lushly-planted garden courtyard, whose enclosed form clearly lends itself to 'rock pool' treatment. Projecting into it now is one of the Smithsons' earliest works at Tecta, the Canteen Porch, conceived along the same lines as Bruchhauser's porches at home.
Its outer walls are faceted in a comparable way, it contains seats on both sides, and its yellow-painted woodwork frames are another lattice variant. As at the Hexenhaus, the new porch is wider than the opening in the canteen wall, so it reads as an extra layer between inside and out.
Protruding on the same side of the courtyard is one of the latest additions, a room for Bruchhauser's father to sit out in while still feeling connected to Tecta's daily life. But the focal point here remains the Yellow Lookout, subject of a Working Detail (AJ 8.6.94).
Its ancestor was the Smithsons' unbuilt Straight Climb Lookout for Kingsbury Water Park in 1977; its progeny include smaller towers at both Tecta and the Hexenhaus (and indirectly the Hexenbesenraum).
It serves both as a lookout and a marker, one of several foci that now locate the factory in its landscape.
As you climb up from the sheltered courtyard, you begin to intercept the breeze and the view. At the top, you come face-toface with the branches of two sugar maples:
'substantial beings', as Smithson says, that completely shade the offices below.
This is the one moment at Tecta when your experience of nature is much like that at the Hexenhaus - you are almost engulfed by the trees.
From the top too you can see a scaleddown yellow tower at the factory's edge, directly overlooking the meadow - another marker that alerts you to the third of the 'empoolings', a radical change in Tecta's relationship with its surroundings. This side was formerly the back of the factory but is now the front; the building has been steadily reorientated.
The meadow had been earmarked for expansion of the industrial park but, as the Smithsons' discussions with Bruchhauser proceeded, he resolved to purchase it to keep it as open green space. Subsequent additions and landscape works have brought it thoroughly into play.
At the meadow's far edge is an unbroken screen of trees beside a brook, with low hills rising beyond - a clear-enough existing demarcation. But to left and right, the space was leaking away, so these boundaries are being strengthened with planting, particularly of silver birches - light-leafed in contrast to the darker trees by the brook.
Smithson also envisages 'an out-andback path system with marker lanterns to keep the sense of the 'internalness' of the meadow space'.
Emerging onto the edge of this field from the factory - 'like fingers onto the landscape, ' says Smithson - are the Sewing Room Porch, the Weaving Room Porch, and the Metal Workshop Porch. Providing rest and recreation areas for Tecta's workers, they are simplified versions of the first Hexenhaus porch, with less elaborate lattices.
All open directly onto the meadow.With its smells of sawn wood, cut metal, lacquer and so forth, you could navigate the Tecta factory in a blindfold: walk outside on the afternoon I was there and you were met by the smell of newly-cut grass. It is this kind of contrast and relief that Bruchhauser wants his workers to enjoy.
Cantilevered at one corner, and reached by a hidden stair, is the Panorama Porch, an extra office space, with the view its name announces. Bruchhauser's own office has, as Smithson puts it, 'a corner chewed out of it', which opens it to the meadow on a diagonal:
an axis emphasised by a new granite path, with an eccentrically-skewed red chair by Wewerka as an eye-catcher at its end.
A view that visitors have as soon as they enter the factory encapsulates the changes there. You look through a glazed corridor to the garden courtyard with its porches and tower, and as the building on its far side is a glazed link, you can see beyond the courtyard, first to the Metal Workshop Porch, then to a chestnut tree, and finally, in the distance, to the far boundary of the site, newly embanked, with its young silver birches. Layer after layer is successively defined.
In support of their entry for the Biblioteca Alexandrina competition in 1989, when these step-by-step German projects were well under way, the Smithsons wrote: 'Throughout the libraries there are devices to bring the sense of the sun, the state of the day, the seasons, to the readers and staff.' It is just this awareness that their work at Tecta fosters.
So many modern buildings are no more rooted to their site than a Post-it note. Tecta is different.
Territorial advantage Returning to Bruchhauser's house before my departure, I climbed up again to the small balcony outside the Hexenbesenraum from where the site, the property, and many of the Smithsons' additions can be seen.
With the different greens of beech and pine, of rhododendron, ivy and moss all in view, a couplet from Andrew Marvell's poem The Garden came to mind: 'Annihilating all that's made/To a green thought in a green shade.' Marvell was writing in 17th-century England; the experience, of course, is timeless.
It is clear that, with its encrustations, holes, and other devices, an 'ordinary' house has become extraordinary. 'I know, ' says Bruchhauser. 'I thankfully realise that every day. I don't have to take holidays or go travelling - I have paradise on earth right here.'
Not many architects get a compliment like that from their client, 17 years down the line.
In an ILAUD essay, 'Gates, Porches, Portals', collected in Italian Thoughts (1993), the Smithsons wrote: 'Territory is easily transgressed: how often it is a question of a window being exposed by the cutting of a tree; the penetration of a patch of open sky by a chimney; a change of the paving of a street where someone played; the brightening of street lighting; a new kind of sound; that can make us, the inhabitants, feel disinherited.'
At both the Hexenhaus and the Tecta factory, the reverse has happened: territory has been consolidated and the inhabitants have come into their own.
Not that the work at either location is complete: 'It's like the Sagrada Familia - never finished, ' says Bruchhauser.
At the Hexenhaus, a Lantern Pavilion will soon be constructed on another of the old terraces; at Tecta, a museum is planned.
Smithson and Bruchhauser will continue step-by-step.
CREDITS CLIENT Axel Bruchhauser ARCHITECT Alison and Peter Smithson: Alison Smithson, Peter Smithson, Lorenzo Wong, Hermann Koch (Hexenbesenraum) STRUCTURAL ENGINEER Bollenger & Grohmann (Hexenbesenraum) CARPENTER Nolte: Herr Schrick SUPPLIERS brickwork Theile; glass Interpane; roof Rauscher