Waasland Shopping Center is located southwest of Antwerp, on the southern edge of the city centre of Sint-Niklaas and has existed since 1972. In 2004, the complex was expanded to 45000 m², with 140 shops, surrounding parking and a parking roof.

Feasibility study

On behalf of the shopping centre owner, we investigated the technically best, most sustainable and economically feasible roof structure taking into account:

the integral sustainability of the superstructure,
the maintenance,
the lifespan,
the accessibility
and energy consumption.

An important part of the study is a thorough investigation of the possibilities of the systems available on the market based on the set parameters, their technical properties and available references.

Based on the analysis of the boundary conditions and available systems, the parking roof system was determined with which to continue the design process.

Challenge

The load-bearing capacity of the envisaged structure allows only a limited building package. Rather, a light package consisting of mortar - EPS system, bituminous waterproofing and poured asphalt was chosen. Today, the roof suffers from infiltrations, indentations and cracking of the poured asphalt.

The feasibility study also examined the possibility of insulating the roof according to current EPB regulations, with a U-value of 0.24 W/m²K. Since the current roof structure was insulated to a limited extent, with a thin roof structure, raising the roof package has a major impact on the connections at the level of the row slope, entrance doors and eaves. In terms of stability, the additional weight should be limited. The insulation must be single-ply to absorb horizontal forces.

Taking this complexity into account, a TOTEM analysis was carried out to investigate the environmental impact of the new roof package. Different insulation thicknesses were compared, assuming an inverted roof with XPS insulation, comparing material and energy costs. The U-value of the different build-ups was adjusted according to the EPB calculations for the roof, to take into account the correction factor for water infiltration between the insulation boards that is possible with an inverted roof. Based on the different assumptions and boundary conditions, it was decided to limit the insulation thickness to 60mm.

The choice for the roof package fell on Zoontjens' modular Pardak®80 system.

Phased works

A phased renovation was deliberately chosen. This allows the roof to remain in use, partially or not, throughout the year. In the busy winter months and during the summer holidays, no work was carried out to keep the total area available.