How can I prevent or clean the fungi that darken the tile joints?

Use grout with antifungal action (e.g. Weber.Color Premium) to prevent or clean fungi that darken tile joints and, after drying, apply a waterproofing product (damp protection) - e.g. Weber.hidrofuge P, or any other water-based product. Maintenance should be carried out every 4 years and this product should be applied again.

Weber.Antimousse, for example, can be used to clean joints without this protection (applied with a paintbrush). Wait one hour to brush the area and then clean with plenty of water. If necessary, repeat the operation.