Unobtrusive roof

It is hard to believe that the membrane cupola, which has been recently added to roof the Kleiner Hof (small inner courtyard) of the Dresden castle, has been occasionally described as too much of a new addition. The above photograph shows how modestly the construction hides behind the castle gable and the ridging due its design and material. Already today several thousand art lovers visit the museums of the state art collections. It was therefore logical to position the foyer, pay and information desks, plus the coffee shop and the museum shop, in or near the Kleine Hof, which is accessible from the exterior on three sides. The required roofing of the courtyard had to take various cornice levels and gable effects into account while not being obtrusively visible from the outside.

The bar construction cupola spans the courtyard, which measures approximately 620 sqm, without additional support. The rack screen frame with flexurally rigid joints is covered by 265 membrane cushions, whose ETFE foil is very transparent, weather-resistant and light-weight. The entire construction weighs around 84 tons. The cushions are kept under a constant pressure of 800 Pascal, while air is supplied directly through the hollow structural steel sections made of square pipe with a cross sectional area of 18 by 18 cm. This rendered an additional air supply system unnecessary.

The layout contour of the cupola resulted from the complex, irregular roof landscape around the courtyard. The view presented below shows how in a transition area the irregularities were incorporated with the help of a precise computer-generated model, which was applied as the basis for accurately fitted implementation. This resulted in a roof featuring a comparatively undisturbed support zone. One by one, the parts of the ensemble will be renovated, reconstructed and  adjusted to contemporary visitor requirements. It will be a key concern to keep signs of this adjustment visible and comprehensible. The courtyard roof is an excellent solution for this demand.
Ursula Baus