PURPOSE: To shorten the curing time by forming bottomed joint sections on a concrete backing material, arranging a water absorbing material at a bottom section, and arranging a back-up material, a sealing material and a water absorbing primer layer on it.

CONSTITUTION: Bottomed joint sections 8 are formed in a lattice pattern on a backing material 1 made of mortar or concrete. A water absorbing material 2 made of water swelling rubber or the like is arranged at the bottom section of the joint section 8. A space is provided on it, and a back-up material layer 3 and a sealing material layer 4 are arranged. A water absorbing primer layer, a coating floor material layer 6 and a finishing material layer 7 are arranged on them. The drying and curing time of the backing material 1 is shortened, and a floor with the coating floor material 6 not peeling off can be obtained.