hello all.anyone use sika waterproofer for rendering as i was supplied with wopping big tub of it today for a job im on.On the insructions it says add 1 litre to every 25kg of cement.Does this work out the same as a take away coffee cups worth(from bp garage) poured into a bucket of water.I no i sound thick but 1 litre of waterproofer sounds like to much to me and that stuff aint cheap.