Platform on new construction, renovation, restoration and transformation
Many postwar gallery flats have renovation needs where preservation of balconies and galleries is not sufficient. An example is Hoog Lindoduin in Scheveningen: with balconies and galleries too cramped and affected by sea salt, the gallery flat is no longer up to date. For Hoog Lindoduin (182 homes), Normteq devised a custom solution based on slender prestressed brackets, between which widened gallery and balcony slabs are placed.
Normteq director Peter Kok says, "The structural weight that was removed was allowed to come back with a small increase in weight. If the balconies and galleries have to be wider as in this case, they have to be made slimmer to arrive at the same weight." Normteq's prestressing solution works on the basis of inserting studs into the building structure, in this case some 1.20 meters deep. Because of the slender consoles, the connection to the structure was critical; therefore, a steel anchor was developed as a structural base element in the load-bearing console. That element connects the building structure and that of the load-bearing console.
"The steel anchoring with prestressing rods is delivered by us to the concrete manufacturer; they pour them in. After curing, the concrete manufacturer trusses the brackets. So they arrive ready-made." The brackets form the opposite sides of the future balcony and gallery floors and are fixed at the intersection of walls and floors. "The loose gallery and balcony slabs bear off the structurally anchored consoles, but are not attached to the building. The pre-tensioned connection provides structural bearing downward. Without steel anchoring with application of prestressing, this would not have succeeded."
A customized solution? "Definitely," says Kok. "Based on proven techniques. First, our work from the existing gallery: filling drilled holes provided by the contractor with a high-quality mortar, inserting the studs with filled mortar and testing the strength. Then the contractor removes the balconies and galleries and installs a temporary support on the floor below. Normteq places the new consoles on the temporary support and adjusts them precisely. Then the zone between existing structure and console is formworked and poured, after curing secured with a nut on the front where the threaded rod is tensioned, the formwork is removed and the zone of the tensioning cavity at the location of the nut is poured. This process repeats itself one floor below. Once at the bottom, our work is over. From below, the contractor begins laying the gallery and balcony slabs between the brackets. Once a floor is laid, the walls are placed from the new gallery, then another layer of balconies and galleries and so on. Floor by floor, the homes are made wind and watertight and work can begin inside the homes."
You have to have a good click with the general contractor for such a concept, Kok continued. "These are not systems offered within a logistics system chosen by the contractor. You have to completely align the approach to execution." That is the case; also, contractor BAM and Normteq have fully involved the municipality of The Hague in design and execution. "We are currently assembling the consoles and with this we hope to be ready in March 2020. This solution is very suitable to apply to similar projects."
