Gyproc Hydro Joint Mix 3.5 Kg Building material or admixture for cement, mortar or waterproofing works — check application on the label Practical DIY construction item Check content (kg/L), color and application in the product name The Hydro Joint Mix from Gyproc is a ready-to-use joint paste with which you can finish green water-resistant Gyproc WR panels for damp areas up to an Order no Available via at Brico Harput.