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Fig. 56: Types of plinth

From top to bottom: platform, "earth pile", basement, box

The plinth above ground

The historical development of the plinth extends from the pragmatic preparation of the building site to personal protection against external dangers (animals, weather, war, etc.), to the architectural, morphology-based apparition of post-Modernism. Hardly any other building component blends technical requirements and architectural intentions in such diverse ways, the origins of which are no longer distinct. Even in the Greek temple, whose platform is a result of the "cultivation" of the terrain, part of its power is derived from its accessibility and hence its three-dimensional conspicuousness. As it developed further, the "earth embankment" held in place by stones grew to the height of a complete storey (e.g. temple in Nîmes, 16 BC) and it was only a matter of time before this plinth was hollowed out to create usable space.

By the middle of the 19th century the plinth storey only remained a subject for palaces and villas, while all other buildings had normal ground floors indistinguishable from the upper floors (cf. housing in the Middle Ages). Regardless of its use (originally ancillary rooms, later also main rooms), the fortified and solid character continued up to the beginning of the 20th century, sometimes in stone (solid or just a facing) or with less expensive rendering.

The plinth below ground

Other reasons for a visible plinth are underground rooms requiring natural ventilation options and the desire to minimise excavation, both of which led to the ground floor being raised. The basement walls grow out of the ground and appear as independent components because they generally have to satisfy different conditions from the facades above (resistance to moisture, earth pressure, etc.). Irrespective of the plinth question, the elevated ground floor is also a theme at the entrance, where the difference in levels that has to be overcome is accommodated either outside the building, within the depth of the facade, or first inside the building, in the lobby or hall. Basement walls hardly distinguishable externally are those that enclose rooms and extend above ground level regardless of the ground f loor slab, and introduce light into the basement by way of hopper-shaped openings.

The I ightwell functions similarly. Used as an intermittent means, the lightwell is not substantially different from the enclosing walls. To simplify construction, it is available as an add-on, prefabricated element in concrete or plastic, but the disadvantage is that the l ightwell creates a hole in the paving, grass, etc., which has to be covered with a grating. Stretched to a linear element running along sections of the facade, the I i ghtwell, provided it is sufficiently wide (1-2 m), is an excellent way of admitting daylight into basements. Basements are thus turned into habitable rooms, with the only difference being the lack of a view.

Fig. 58: Powerful structural link between substructure and superstructure with different uses (residential and prestigious versus basement)

Hardouin-Mansart, de Cotte: Grand Trianon, Versailles (F), 1687

Fig. 58: Powerful structural link between substructure and superstructure with different uses (residential and prestigious versus basement)

Hardouin-Mansart, de Cotte: Grand Trianon, Versailles (F), 1687

Fig. 60: Lightwell with fully habitable basement rooms

Steger & Egender: Art School, Zurich (CH), 1933

Fig. 60: Lightwell with fully habitable basement rooms

Steger & Egender: Art School, Zurich (CH), 1933

Fig. 62: The lightwell as an Indication of a basement

Marques & Zurkirchen: Kraan-Lang House, Emmenbrücke (CH), 1994

Fig. 62: The lightwell as an Indication of a basement

Marques & Zurkirchen: Kraan-Lang House, Emmenbrücke (CH), 1994

The "transferred" plinth

If the base of the I ightwell drops to the level of the basement floor slab, this creates an accessible external space, an arrangement with a long tradition in Great Britain, for instance. Reached separately via an external stair, such basements are suitable as company flats or for use by small businesses. The requirements the "basement wall" has to meet are now no different from those of the facade above. With such an arrangement on all sides we obtain a "tank" in which the building stands untouched by the geological conditions and where all storeys can be constructed according to the same principles (e.g. timber engineering).

Fig. 61: The "lightwell" here has been extended to form an accessible garden.

Steger & Egender: Art School, Zurich (CH), 1933

Fig. 61: The "lightwell" here has been extended to form an accessible garden.

Steger & Egender: Art School, Zurich (CH), 1933

The suppressed plinth

In contemporary architecture the plinth theme is mainly relevant only on a constructional/technical level. If the topographical conditions are not conducive to the creation of, for example, a plinth storey, the structural arrangement is suppressed, sometimes at great expense. Increasingly, buildings are being seen more as (art-related) objects than as structures; but they are still built in the same way. We are mostly using the same methods as we did 50 years ago, at best with only minor modifications; the difference is that on the path to maximum formalisation they frequently ignore the "rules of architecture".

Regarding the building as an object emphasises three principles of the terrain-structure relationship: growing out of the terrain, placed on the terrain, and detached from the terrain. From the viewpoint of building technology, growing out of the terrain presents the greatest problems because the continuous, consistent "outer skin" is subjected to different requirements: weather resistance and protection against mechanical damage above ground level, moisture and earth pressure below. Homogeneous materials such as in situ concrete and render (waterproof render and/or moisture-resistant substrate) present few problems. Jointed constructions left exposed present many more difficulties: masonry, precast concrete elements and timber, sheet metal or other lightweight claddings. The weak spots are leaking joints but also the inadequate moisture resistance of the materials themselves (bleeding, rot, etc.).

On the other hand we can detach the building from the ground by employing a whole range of methods, from strip footings above ground to storey-high pilotis, and hence eliminate the "ground-related" effects. Between these two extremes we can place the building on the terrain, an arrangement which through the ground floor slab - and possibly even through a basement - clearly has the effect of anchoring the structure to the ground. However, the fact that the f acade cladding stops short of the ground conveys the impression of an object placed on the ground.

Fig. 66: Rendered thermal insulation with stone plinth

Dolf Schnebli: apartment block, Baden (CH), 1990

Fig. 66: Rendered thermal insulation with stone plinth

Dolf Schnebli: apartment block, Baden (CH), 1990

Our image of the plinth

The tendency towards a formalised object is not least a reaction to post-Modernism, the protagonists of which, with comparable technical means, attempted to create not formalisation but a nonexistent structural versatility in order to achieve the image of the traditional "building" (plinth, standard and attic storey, distinguished only by their surface textures).

Even if only in the form of cladding (just a few centimetres thick), this type of plinth is more than just a way of distinguishing the facade because such an arrangement protects the facade against soiling as well as mechanical damage.

The unavoidable plinth

Ignoring architectural preferences, it may well be that the topography determines the need for a plinth, depending on

Fig. 68: The concrete plinth is the visible part of the excavation in which this timber building stands. Horizontal boards positioned at the steps in the concrete cover the concrete/timber junctions.

Peter Zumthor: Gugalun House, Versam (CH), 1994

Fig. 68: The concrete plinth is the visible part of the excavation in which this timber building stands. Horizontal boards positioned at the steps in the concrete cover the concrete/timber junctions.

Peter Zumthor: Gugalun House, Versam (CH), 1994

the type of construction. Whereas on flat ground it is still easy to suppress or reduce the plinth, on sloping ground we are immediately faced by the question of whether the difference in levels can be accommodated by forming a true plinth storey or whether the plinth should follow the line of the terrain. The former suggests storeys with different utilisation, while the latter raises structural issues: is the plinth the foundation for the facade above, and hence loadbearing, or is it a "protective screen" to ward off the problems of earth pressure and moisture?

Fig. 69: Plinth forms for sloping sites a) Building in open excavation ("protective screen")

b) Building, or rather superstructure, supported on sides of excavation c) "Basement storey" supporting upper floor

Fig. 67: Painted concrete and ceramic tiles as protection against weather and soiling, and also providing a figurative plinth function

Otto Rudolf Salvisberg: apartment block, Zurich (CH), 1936

Fig. 69: Plinth forms for sloping sites a) Building in open excavation ("protective screen")

b) Building, or rather superstructure, supported on sides of excavation c) "Basement storey" supporting upper floor

Building performance issues

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