The need of waterproofing roofs, terraces, industrial sheds, bridges, viaducts, basins, walls against the ground, fluvial channels, tunnels, remakings of old sheath coverings, expansion joints of any dimension, shape and nature, is well known.

It is the aim of the present invention to realize an mulsion that may be applied in all mentioned cases, of a highly adhesive kind and that will never loose in time its adhesiveness.

The aim set forth is reached by the mulsion according to the present invention, comprising a percentage of bitumen in weight of 35% to 70%, modified with a percentage variable from 3% to 1 5% of elastomers (SBS) and spray applied with a two-nozzle spray, one for the mulsion and the other one for the catalyst, consisting of calcium chloride dissolved in water, so that the meeting of the two sprays on the surface to be treated obtains an immediate catalization. The mulsion according to the present invention may be applied on any kind of structure, cement mortar, sheet- zinc, already existing sheaths, allowing to perform in short times waterproofing of great surfaces.

Above mentioned spray with two nozzles is provided with flexible pipes of appropriate width, thus allowing to leave the working unit downstairs of far from the application point. Due to the calcium chloride dissolve in the water, the sprayed product catalyzes as soon as it gets into contact with the application plane sticking strongly to the same, thus forming an elastic monolithic coat on whatever surface applied, of the desired thickness (suggested thickness: 4 mm ca.). The coat thus obtained is insoluble if it gets into contact with water, even a few seconds only after spraying, like in case of sudden rain.