Economical liquid composite waterproofing based on recycled polystyrene, which can be easily applied with a roller or brush, capable of adhering to multiple surfaces, with a performance equal to or better than its competitors, but with better thermal, optical and mechanical properties. It has the capacity to cover up to 2 m2 per liter of product and is also capable of perfectly sealing cracks up to 1.5 mm wide for a period of more than 8 months, according to our most recent studies. The product was improved with additives that, according to various analyses, reflects 99.9% of UV radiation (which is the main cause of polystyrene degradation), as well as being flame retardant and reflecting more than 90% of infrared light, which , as a whole, the temperature difference between exterior and interior decreases by more than 20 °C, even in extremely hot conditions, such as in the Yucatan Peninsula. Given its reliability, reinforcing mesh is not required, which further reduces the installation cost, and can be applied by anyone without high technical knowledge and using minimal personal protection equipment.