1. Polystyrene boards - versatile - easy to install - 100% waterproof - resistant to rot - lightweight. 2. Used in floors, walls, and ceilings, ideal for bathrooms and damp places. The best alternative to plasterboard and cement board. Sizes: 120CM/250CM, 250/60CM. Thicknesses: 12MM, 20MM, 30MM, 40MM, 50MM. Used for custom sinks and tables.