Flooring material, comprising board shaped floor elements which are intended to be joined vertically

Flooring material intended to be joined vertically comprising floor boards with an essentially square, rectangular or rhombodial shape, which floor boards comprise edges, horizontal lower side and a horizontal decorative upper surface, whereby the floor boards further comprise lower joining lips at two adjacent edges while the two remaining edges are provided with upper joining lips, the lower joining lips and upper joining lips each having a shape to permit assembly in a vertical direction, wherein the lower joining lips are provided with essentially vertical lower lip surfaces arranged parallel to the closest edge which lower lip surfaces are intended to interact with mainly vertical upper lip surfaces arranged on the upper joining lips so that two joined adjacent floor boards are locked together in a horizontal direction and that the joining lips are provided with one or more heels intended to snap join with recesses adapted thereto which, by being provided with essentially horizontal locking surfaces, limits vertical movement between two joined adjacent floor boards, whereby the floor boards are joinable by pressing vertically downwards a first floor board with respect a second floor board to mate the joining lips of the first floor board with the joining lips of the second floor board.