25L Sika No1 Waterproofer

The original waterproofing additive for cement based mixes of concrete, render and screed. A real trade classic waterproofer. Unchanged over 100 years! Dilute with water and dose to the mix. Works by allowing a small amount of water to penetrate and cause swelling of the silicate molecules which, as they grow, block the pores and thus resist water under pressure.