The materials commonly used to check dampness can be divided into the following four categories (a) Flexible material Material like bitumen felts (which may be Hessian based or fibre/glass fibre based), plastic sheeting (polythene sheet) etc (b) Semi rigid materials Materials like mastic asphalts or combination of materials or layers. (c) Rigid materials Materials like first class bricks, stones, slates, cement concrete etc (d)Grout materials Grout consists of cement slurry and acrylic based chemical or polymers. Hence, cement concrete falls under the category of rigid materials when checking the dampness of a material.