Mastery in roofing and insulation

Vertical gardens Wonderwoods should restore biodiversity in Utrecht

Anyone who came near Utrecht's Central Station in recent years saw mostly pigeons. Biodiversity was almost zero. The residential towers of project Wonderwoord should soon change this. Thanks to no less than a hectare of greenery on the facades, on the balconies and in the roof parks, a new ecosystem will in fact be created in the city, with plants and trees attracting large numbers of insects and birds. To make Wonderwoods' green ambition possible, numerous specialists are putting their best foot forward. These include the roofing specialists at BOKO Dakbedekkers, who, under the leadership of foreman Ron Karsten and in close construction team collaboration, are realizing a masterpiece in roofing.

Wonderwoods is inspired by Milan's "Bosco Verticale," also designed by Stefano Boeri. The 105-meter-high Boeri Tower will have a green facade with no less than 4 (!) kilometers of planters and 155 tree boxes. Nearly 6,000 m2 of rooftop park will also be created, spread over several floors. The 70-meter-high MVSA Tower will feature nine interior gardens. "It takes a special piece of craftsmanship to achieve a solid waterproofing of all the roofs, balconies and terraces," says Rob Bootsman, Managing Director of BOKO Roofing Contractors. "But here, too, our roofing specialists do not turn their hand around." Within project Wonderwoods, BOKO Dakbedekkers is responsible for the roofing and insulation. "An important question here was to make all the details seamless and watertight." Over 80% of the work has now been completed. Together with Bootsman, we are already looking back on a challenging project, which involved very pleasant cooperation with all construction team partners. Both technically and logistically, in which unexpected matters were handled very energetically.

Right the first time

Because of the many tree and planters, Wonderwoods involved a complex job with major execution risks, he says. "A major challenge, for example, were the precast concrete tree tubs, which fall over the concrete ridges. The roofing on these ridges had to be ready before the installation of the tree tubs. After installation, our roofing specialists also had to provide waterproofing via a manhole. A job that we might only encounter once in a lifetime and it also had to be done right the first time, because after the trees were placed, we couldn't access them again. That's why we went through all the details very carefully in advance with the construction team and coordinated them. In about three years' time we arrived - in collaboration with Boele & van Eesteren and Koninklijke Ginkel Groep, among others - at the most optimal solution."

Very high demands

The Boeri Tower and MVSA Tower together have nearly 6,000 square meters of roof area, while the basement deck has an area of 1,000 square meters. "All concrete roofs are finished with intensive greening, which places very high demands on the roofing," said Bootsman. "For the roof structure, a bonded cast bituminous vapor retarder was chosen in combination with an Isomix Plus roof system (Rc: 6.3 m2.k/W) and two layers of Wédéflex D4 (APP) roofing. A similar construction is used on the balconies and terraces, but with PIR slope insulation and tiles. The details in particular, such as the edge finishes, determine the quality, reliability and durability of the roof system here."

'Flying gardeners'

Wonderwoods' landscaping will soon be handled by so-called "flying gardeners. "To ensure that they can reach everything properly and safely, fixed Rope Access facilities will be installed at the eaves and on the floors," concludes Bootsman. "BOKO Roofers takes care of the waterproofing of all supports. Thus, we go for gold in every area." A DAKMERK MULTI warranty is issued on the entire roof work.