Injections

First stage: stop the water

The highly reactive single-component polyurethane resin cures on contact with moisture, developing a tough foam that can reach up to forty times its initial volume. The reaction starts within roughly twenty seconds. It serves to stop active water ingress, not to seal permanently: the foam has good immediate holding power but not the lasting elasticity a crack that keeps moving requires.

Second stage: seal

Once the water is stopped, a second injection follows on the crack with a low-viscosity two-component resin, in a 1:1 ratio. Low viscosity lets it penetrate deep even into fine cracks, and soft-elastic curing lets it follow subsequent movement without detaching. It adheres to both dry and damp substrates.

The injection technique

Injection is carried out through packers inserted into inclined holes that intercept the crack at mid-thickness, placed alternately on the two sides. Work proceeds from the bottom up, one packer at a time, until the product is seen coming out of the next one.

In masonry, where the purpose is a barrier against rising damp rather than sealing a crack, dedicated packers with a ball non-return valve are used, injecting gel or liquid silane at low pressure.