A method for constructing a closed steel sheet structure, wherein the closed steel sheet structure comprises a space to be filled with concrete to form said steel concrete composite structure and wherein the method comprises providing a first steel plate having a first outer surface and a first inner surface that is parallel with the first outer surface, attaching reinforcing members to the first inner surface of the first steel plate so that the reinforcing members project perpendicularly from the first inner surface of the first steel plate, providing the reinforcing members with supporting members, providing a second steel plate having a second outer surface and a second inner surface that is parallel with the second outer surface, providing the second steel plate with first openings between the second outer surface and the second inner surface of the second steel plate, supporting the second steel plate on the supporting members provided at the reinforcing members projecting from the first inner surface of the first steel plate so that the second inner surface of the second steel plate faces the first inner surface of the first steel plate, so that said space is formed between the first inner surface of the first steel plate and the second inner surface of the second steel plate, and so that at least one of the supporting members and the reinforcing members covers the first openings at the second inner surface of the second steel plate, attaching the second steel plate to at least one of the supporting members and the reinforcing members via the first openings in the second steel plate from the side of the second outer surface of the second steel plate of the closed steel sheet structure, and providing reinforcing members and supporting members in the form of profile elements having a web plate forming the reinforcing member and a first flange extending perpendicularly in relation to the web plate and forming the supporting member, characterized by profile elements forming first profile elements, which web plate extending in a first direction between the first steel plate and the second steel plate, and by profile elements forming second profile elements, which web plate extending in a second direction between the first steel plate and the second steel plate, wherein the second direction extend transversely to the first direction. providing a first steel plate having a first outer surface and a first inner surface that is parallel with the first outer surface, attaching reinforcing members to the first inner surface of the first steel plate so that the reinforcing members project perpendicularly from the first inner surface of the first steel plate, providing the reinforcing members with supporting members, providing a second steel plate having a second outer surface and a second inner surface that is parallel with the second outer surface, providing the second steel plate with first openings between the second outer surface and the second inner surface of the second steel plate, supporting the second steel plate on the supporting members provided at the reinforcing members projecting from the first inner surface of the first steel plate so that the second inner surface of the second steel plate faces the first inner surface of the first steel plate, so that said space is formed between the first inner surface of the first steel plate and the second inner surface of the second steel plate, and so that at least one of the supporting members and the reinforcing members covers the first openings at the second inner surface of the second steel plate, attaching the second steel plate to at least one of the supporting members and the reinforcing members via the first openings in the second steel plate from the side of the second outer surface of the second steel plate of the closed steel sheet structure, and providing reinforcing members and supporting members in the form of profile elements having a web plate forming the reinforcing member and a first flange extending perpendicularly in relation to the web plate and forming the supporting member, characterized by profile elements forming first profile elements, which web plate extending in a first direction between the first steel plate and the second steel plate, and by profile elements forming second profile elements, which web plate extending in a second direction between the first steel plate and the second steel plate, wherein the second direction extend transversely to the first direction.