The choice for untreated copper as the facade material was based on a number of criteria. Naturally, the material needed to be low maintenance. The architect wanted a visually smooth material which would reflect the light, from morning and evening, spring and autumn, dark clouds and sun, the building was designed to show the many changes.
Residential towers in red copper
The residential towers in the Den Helder area meant that a relatively short construction time was required, fixed at 242 working days. In order to realise this, Bot Bouw from Heerhugowaard, devised a logistical solution, where the prefabricated wall elements were brought to site allowing each floor to be completed in 6 or 7 days. The elements, 3,90m width and onestorey high, were supplied to the site, inclusive of the glazed frames and the wood substrate for the copper.
The copper was supplied in coils to the construction site. Ridder Metalen Dak – and Wandsystemen BV from Zwaag - made up the copper elements to the right size in a special facility located on the site. All the copperwork used clips, allowing movement of the metal for thermal expansion.
The residential towers have horizontal cladding in 3 different widths : 33, 43 and 53cm. The horizontal ribbon windows fit in the 43cm width. The copper is only 0.6mm thick and is easily cut and folded, according to Pieter Spijker of Ridder Metalen Dak- and Wandsystemen: "Titanium is much thicker and harder than copper, it is very hard to fold. In order to bring the facade to site we have our own lift scaffold, so that we can work independently from the construction crane. The elements are prepared at ground level and then brought up. Using specialist tools we form the seams on the copper, completing around 10m² per man per day, including the facade material around the window frames.
An unusal thing with this project is the fact that the copper around the windows is a continuation of the facade of the building, says the Spijker. "The horizontal cladding runs up to the window frames, then underneath and on top, as well as on the vertical faces of the windows. The upper- and under-cladding of the window frames uses a perforated copper strip, which makes it possible to have good ventilation behind the copper cladding".
The pre-fabricated sections are fixed with stainless steel clips. Inert materials have been used throughout to ensure that disimilar metals are not in direct contact.. As copper must have a chance to expand and contract, some vertical spaces have been left at various locations to accommodate expansion.
Spijker : "The copper cladding, because of its thickness of less than 1mm, gives a slight speckled effect, it is never entirely flat. For an architect, it is important that he has an idea of how the project will look on completion".