Projects: Historic Preservation



ROOFING CONTRACTOR: Vandekerckhove of Ingelmunster





    ▪▪ DELTA-TRELA, which can be used for ventilated and unventilated steep roofs with metal claddings, as well as for metal façades, ensures protection against moisture build-up and white rust formation. The 8-millimeter-thick randomly oriented polypropylene fiber mat with studded structure provides an additional drainage plane below the roofing material and allows unimpeded movement during thermal expansion and contraction. Because of its special structure, the material can be used independently of the cladding alignment when shaping details. The drumming noises of rain and hail are muffled by 15 decibels. With a rating of 120 perms for the carrier membrane, residual moisture that may be present in the wooden supporting structure can safely migrate outward.



Right from the start of his reign, King Leopold II, who ruled Belgium from 1865 to 1909, had ambitious urban-planning projects in mind for the capital city of his still young country. Brussels, which appeared too provincial and compartmentalized for his taste, would impress by projecting the economic status of the country outward—after all, Belgium was one of the top five economic powers in the world at that time.

As one of the first projects, a new Palace of Justice with a representational design was to be built on the terrain of the Gallows Hill. The king commissioned his acquaintance, the architect Joseph Poelaert, for this purpose. Poelaert designed a building on a gigantic scale with a floor plan of 280,000 square feet and crowned it with a majestic dome that towered over its surroundings by more than 328 feet. It was the largest building in the world built in the 19th century and still is the largest of its kind in Europe. Today, the building is protected and its inclusion in the list of UNESCO World Heritage Sites is pending.

BUT TIME is not easily impressed by the grandeur of a project. The building structure has decayed over time and has been unstable for decades. Only some areas are being used. From the outside, its desolate state is clearly evident by the large amount of protective roofing and scaffolding that has enveloped large parts of the building since the middle of the 1980s. Since then, the most urgent renovation, repair, and restoration work has been carried out continuously on the interior and exterior.

A few years ago, the decision was made to replace all roof areas covered with rolled zinc in a sequence of several stages. The work began in March 2012. The tradesmen faced a daunting task. The strongly segmented building consists of numerous individual parts that are grouped around eight interior courts. They are covered by saddle and hipped roofs that have different slopes and are arranged at varying heights. The 27 courtrooms and more than 200 additional rooms needed as much protection as possible from the effects of the weather during the construction work. Under these circumstances, it appeared advisable to perform as much of the work sequence as possible on the construction site itself. Temporary workshops were set up on the roof where the titanium zinc in sheets and rolls was processed.

During installation, the design and construction specifications of the original building stock were followed strictly down to every detail. The characteristic Belgian roll cap roofing was to reflect precisely the original design of the profile, the widths and lengths of its rows.

MANY OF the design details proved quite challenging. Most of the roof surfaces have a slope of only 3 degrees and were constructed with staggered drops to avoid the difficult waterproofing that the transverse joints required on this flat slope. It was planned to recapture faithfully the original workmanship of this variant, too.

A structured separating underlayment layer was installed as the only “modern” concession over the entire area between the existing timber framework, which was to be preserved, and the new sheet metal roofing.

The old metal roofing was removed in as small sections as possible. Then, the underlayment was rolled out and fastened on the timber framework. The wooden battens, which had been sized in the workshop for the specific installation site, were screwed on top and fastening straps were attached. The titanium zinc sections were laid into the fields immediately after and held in place with the fastening straps. Finally, the site-fabricated caps were pushed or clipped on. In this way, only a few field widths were open at any given time and could simply be covered with tarps to protect the rooms underneath during work interruptions or inclement weather.

The construction time has been estimated at a total of 20 to 24 months. Completion is expected for late 2014.


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