| CPC E04F 15/02016 (2013.01) [E04F 15/02033 (2013.01); E04F 15/02038 (2013.01); E04F 2201/0146 (2013.01); E04F 2201/023 (2013.01); E04F 2201/042 (2013.01); E04F 2201/043 (2013.01); E04F 2290/00 (2013.01)] | 23 Claims |

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1. A panel comprising:
a. at least one first edge and at least one opposite second edge, wherein said first edge comprises a first upper edge portion, wherein said second edge comprises a second upper edge portion;
b. at least one first coupling part arranged on said first edge, and at least one second coupling part arranged on said opposite second edge, wherein the first coupling part of said panel and the second coupling part of another panel are arranged to be coupled to provide a locking of two coupled panels, such that a least a part of the first upper edge portion faces at least a part of the second upper edge portion to form a top seam in between the panels;
c. wherein at least a part of at least one upper edge portion is provided with at least one expandable material layer, the at least one expandable material layer comprising at least one material configured to expand or swell upon contact with moisture,
wherein the at least one expandable material layer provided is partially covered by at least one protective layer and wherein an exposed portion of said expandable material layer is in direct contact with an atmosphere surrounding the expandable material layer.
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