Is this good for a fake rock? would i still need to seal it even though it says its waterproof??
http://www.focusdiy.co.uk/Decorating-Accessories/Unibond-Sandstone-Floor-Tile-Quick-grout-5kg/invt/185070
http://www.focusdiy.co.uk/Decorating-Accessories/Unibond-Sandstone-Floor-Tile-Quick-grout-5kg/invt/185070