Locking system and flooring board

A locking system for mechanical joining of rectangular floorboards having a body, long edges and short edges, the long edges being perpendicular to the short edges, the locking system comprising:

• a tongue and a tongue groove for vertical locking of two long joint edges of two adjacent floorboards, wherein the tongue and the tongue groove form a tongue-and-groove joint, and the tongue-and-groove joint is configured so that there is in the groove, in the joined state, a space below the tongue,
• for horizontal mechanical joining of the long joint edges, a locking groove formed in the underside of a first long joint edge, and a portion projecting from a second long joint edge, the projecting portion extending from the body of the floorboard and supporting, at a distance from the second long joint edge, a locking element cooperating with the locking groove,
• wherein the tongue is arranged on the second long joint edge, the groove is arranged on the first long edge, the projecting portion is integrally formed in one piece with the floorboard by working of the body of the board,
• wherein the tongue and the tongue groove have cooperating upper abutment surfaces and cooperating lower abutment surfaces for vertical locking of two long joint edges of two adjacent floorboards, the upper and lower abutment surfaces being essentially parallel with the principal plane of the floorboards,
• wherein, in a joined state, the cooperating upper abutment surfaces are limited horizontally inwards from one of the long joint edges and horizontally outwards to the one long joint edge by an inner vertical plane and an outer vertical plane, respectively, and the lower abutment surfaces are positioned essentially outside the outer vertical plane.