Locking system for floorboards

A locking system for mechanical joining of floorboards, said locking system comprising:

• for horizontal joining of a first and a second joint edge portion of a first and a second floorboard respectively at a vertical joint plane:
• a locking groove which is formed in the underside of said second board and extends parallel with and at a distance from said vertical joint plane at said second joint edge, a strip integrally formed with a core of said first board, which strip at said first joint edge projects from said vertical joint plane and supports an upwardly directed locking element with a locking surface for coaction with a locking surface in said locking groove, and
• first contact surfaces at the vertical joint plane;
• and
• for vertical joining of the first and second joint edge portions:
• a tongue which extends from the joint plane and having an upper tongue surface and a lower tongue surface,
• a tongue groove adapted to coact with said tongue, the tongue groove having an upper tongue groove surface and a lower tongue groove surface, and
• coacting second contact surfaces positioned in said tongue groove and on said tongue,
• wherein the locking surfaces, the coacting second contact surfaces, and the first contact surfaces at the vertical joint plane are configured to be operative surfaces in a laid floor;
• and
• further comprising:
• a first inoperative space in the locking system between the first coacting contact surfaces and the second coacting contact surfaces when the first and the second floorboards are joined horizontally and vertically,
• a second inoperative space in the locking system between the second coacting contact surfaces and the locking surfaces when the first and the second floorboards are joined horizontally and vertically, and
• the lower tongue groove surface and the lower tongue surface are not in direct contact with each other when the first and the second floorboards are joined horizontally and vertically,
• wherein said inoperative spaces are configured to be spaced from each other when the first and the second floorboards are joined horizontally and vertically.