Windmill foundation grouting waterproofing Grout is an extra high properties material that is normally used in wind farm construction just below the tower flange, above the foundation. It is a transition material, designed to have a very high fatigue resistance. All the dynamic loads need to be transferred and absorbed by the grout connecting the tower to the foundation structure. Grout is volume stable and his resistance grow very quickly (it is faster than normal concrete in achieving a relevant percentage of his final value, and it has a very low porosity and water absorption.