Waterproofing the underground levels of the Upper West Tower in Berlin
The 118m high Upper West Tower will be one of the tallest buildings in Berlin. When completed in 2016, the 34 story building on Breitscheid Square will offer a panoramic view of Kurfuerstendamm.
It took almost a year to excavate the 16m deep pit into an approx. 3,500m² large excavation area and to stabilize it using sheet piling. The design of the building included four entire basement floors.
In order to carry out the challenging task of waterproofing the underground levels, the general contractor decided to use conceptual solutions with contec® Waterproofing Systems as well as recostal® Formwork Systems by DSI Porta Westfalica.
Sectoral Planning using contec® Waterproofing Systems
A waterproofed concrete structure known as white tank system had to be constructed together with a waterproofing membrane for poured concrete according to the guidelines for watertight structures. DSI designed a concept for the complete watertight structure of the building, including a detailed plan for the outer surface seal and the interior joint structures. The Concept included contec® Waterproofing Systems.
Due to the projected high level use of the building, the high strain resulting from 13m of hydrostatic pressure and the requirement to also prevent damp patches around cracks, joints and surfaces in the underground parking garage, the Preprufe® waterproofing membrane for poured concrete was specified as the primary waterproofing for the exterior tank shaped structure. This way, the minimum requirement of a calculated crack width of 0.3mm could be assumed for designing the watertight concrete structure, which resulted in a reduced reinforcement steel demand for the complete watertight structure.
Preprufe® Waterproofing Membrane for Poured Concrete as Primary Sealant
The Preprufe® waterproofing membrane for poured concrete has been effectively used in a large variety of climatic conditions around the world for over 20 years. The multilayer waterproofing membrane consists of robust HDPE and is thus watertight, gas proof and extremely elastic. This way, even post-formed cracks of up to 5mm in concrete structures can be reliably bridged and waterproofed. This unique selling solution ensures a maximum degree of effectiveness in the waterproofing of buildings for all planned and unplanned cracks in watertight structures.
In contrast to comparable products, the Preprufe® waterproofing membrane for poured concrete is nearly diffusion resistant. The Sd value is significantly higher than that of comparable sealing membranes for poured concrete and thus results in a vapour diffusion resistance that is up to 15 times higher – the decisive criterion when choosing waterproofing materials for high quality construction projects.
The unique bond to concrete structures is very advantageous. This adhesion seal is created by a full-surface, permanent adhesive bond between the hardening concrete and the Preprufe® waterproofing membrane. Water ingress can be ruled out even if local damage occurs. In addition, the concrete structure is permanently protected from aggressive media.
The material is very robust and resistant, thus permitting installation in any kind of weather condition. When badly soiled, the product’s full functionality can be re-established by simple cleaning. Furthermore, the self-adhesive selvage on one edge, which does not require any special shaped parts or tools, ensures an easy and safe handling during installation. With only two types of membrane, the product line is straightforward and simple – even in detail. Consequently, faster construction cycles can be planned.
Cost-effective and efficient Installation of Construction Joints using recostal® Formwork Systems
Trapezoidally profiled recostal® 2000 GTF-Z formwork units were used during the installation of the construction joints in the up to 3.00m thick base slab. The profile meets the demands of Eurocode 2 for the highest category “key profiled”.
The customized, self-supporting recostal® formwork units ensured a trouble-free installation and fast construction progress thanks to an optimized installation sequence. Since the recostal® formwork units for the first area pour were factory-fitted with tie bars, work continued quickly and with no obstructions in the second section.
contaflexactiv Metal Waterstops with a sodium bentonite coating are integrated in the recostal® formwork units. The coating is characterized by its high expanding capacity and ensures effective waterproofing without delay in the critical construction joint zone. The permanent activation behavior in changing water levels has been established.
For leakage prevention in the lower 13 layers of reinforcement with different diameters and centers, the DSI experts also developed a project-related, installation optimized solution consisting of reinforced expanded metal elements that can be combined as system components with the recostal® formwork units and the Preprufe® waterproofing membrane without any problems. For the construction joint stop ends in the walls of the four basement floors, recostal® 1000 F activ formwork units, which form part of the system, were used.
The complete concept for the high-grade waterproofing of the building developed by DSI convinced the general contractor. The comprehensive, complete and singlesource waterproofing system by DSI, which was planned, produced and supplied just in time, permitted an economic, efficient and effective waterproofing of the Upper West Tower.