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Damp proof course in double-shell brickwork
The Clinical Center of Hanover Nordstadt looks back on an over 100-year long tradition. Since its opening back in 1895 the Nordstadt Hospital has undergone constant changes due to war damage and has been provided with numerous new buildings and extensions.
In 2005, extensive rebuildings in the main building’s basement were necessary when the new surgery ward was built. The old brickwork of the external walls showed severe damage caused by capillary rising moisture. This is why it was planned to install a post-construction water stop in the basement rooms concerned. One major problem was that the hollow layer between the load-bearing inner shell and the facing brickwork also reached into the basement bottom area below the ground top edge.
First of all it was decided to fill the gap between the walls with casting foam WEBAC® 2260 before installing the actual horizontal water stop. The casting foam provided for a pressure-resistant, closed-cell covering which prevented the injection material from flowing into the space between the shells.
The foam has up to 1,8 N/mm² compressive strength and thus ensured sufficient resistance to the injection pressure. At the same time the material functions as vertical barrier to permanently prevent moisture from penetrating the space between the shells. A positive side effect is that the external wall’s calorific value could be improved thanks to the material’s good insulating qualities. This reduces the risk of condensation water formation in the rooms.
The company Lömpel, which is based in Neu-Isenburg/Germany, was commissioned with the implementation of the job and drilled holes immediately above the basement bottom which reached into the space between the shells. At a height of approx. 50 cm, more holes were drilled so that the material could be injected layer by layer. Additional holes were provided to allow for good ventilation and a visual inspection of the injection procedure. At the selected adjustment, the material increased its volume about 14-times and the hollow layer was successfully filled up to the height of the ground top edge.
Following the curing process of the casting foam, WEBAC PU Injection Resin was used to form a barrier to guard against capillary rising moisture.
Polyurethane resins are an ideal and cost-effective solution for demanding sealing tasks. Thanks to the combination of foaming and flexible resins both cavities and capillary pores are filled permanently. Damage due to moisture in undergrade construction elements can thus be durably eliminated..