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PU Casting Foam Resins

PU casting resin for filling cavities

WEBAC PU casting resin is based on polyurethane resin and is used for filling cavities and for improving thermal insulation. The cast resin is also used for stabilizing masonry. The casting material is characterized by its high strength and fast curing process.

The cast resin shows good compatibility with concrete, steel, masonry mortars, foil and cable sheathing. WEBAC PU casting resin withstands salts, lyes and acids in the usual concentrations found in building structures.


Preparatory work

Structural analysis before casting or injecting the cast resin: 

  • Structural condition
  • Moisture condition
  • Voids and leaks

This provides information on: 

  • Selection of suitable filling materials
  • Choice of filler openings/lances
  • Positioning of drill holes

Substrates must be dry or residually damp and free of loose particles and separative substances such as oil, grease and similar. The temperature of the structural elements must not fall below 5 °C. The cavities to be filled must be properly patched and leak free.

Application of PU casting resin

The casting material is applied either via filler openings or by means of injection with a 2C pump via drill holes or injection lances / injection packers. In case of higher filling levels the material should be introduced layer by layer. The reaction speed is influenced by the temperature of the material and the structural element. Higher temperatures accelerate, lower temperatures decelerate the reaction. Always inject pure WEBAC casting material without any traces of residues from cleaning agents or other foreign matter.


  • Introduce the mixed casting material into the voids and cavities via filler openings

Application by 2C pump

  • Provide for an adequate volume flow so that components A and B are mixed in the mixing device (static mixer) until homogenous

Final work 

  • Close the drill holes with suitable mineral building materials

Exemplary application of PU casting resin

One example of the successful use of WEBAC PU casting resin is the renovation of the hospital Klinikum Hannover Nordstadt. The hospital was opened back in 1895 and underwent a lot of modifications due to war damage, the construction of new buildings and conversions. When the new surgery building was constructed extensive conversions in the basement of the main building were necessary.

The old external brick walls showed severe damage caused by capillary rising moisture. The affected basement rooms therefore needed to be provided with a post-construction damp proof course (dpc). The hollow layer between the load-bearing inner shell and the fair-faced brickwork reached down to below the ground top edge, right into the area of the basement floor.

WEBAC PU casting resin was used to fill this void, obtaining a pressure-resistant and closed-cell sealant. The cast resin served as material for the required damp proof course and as vertical barrier/sealant at the same time.