WHAT IS A WATERPROOF ADDITIVE? What is a waterproof additive?
Submitted by: Les Collins Answer: A waterproof additive, also sometimes known as a salt retardant additive, is usually a liquid (powder versions are available) that is added to the gauging (mixing) water used to mix a sand and cement render. Most waterproof additives are to all intents and purposes soaps and they act as a plasticizer. They work by entraining small air bubbles in the mix which act as tiny ball-bearings enabling the gritty sand particles to rub against each other with relative ease. This means that less water is required in the mix for ‘workability’. It is important to note however that waterproof additives are very much secondary in the creation of a waterproof render. The most important aspect is the sand and cement ratios used and the type of sand. The recommended specification that should be used following a remedial DPC is 3 parts of sharp washed well graded sand (to BS 1199) to 1 part of cement. This ratio and type of sand means that there is sufficient cement (pas
