A mold arrangement for precasting load bearing wall panels, the mold arrangement comprising: a shrinkable core comprising a first wall and a second wall being spaced from to each other by a first distance to define an internal region in-between; a first side element and a second side element arranged to close opposite edge portions of the spaced first wall and second wall such that fluid concrete cannot pass the opposite edge portions to get into the internal region, the first side element and second side element being spaced by a second distance; and a spacing element configured to vary at least one of the first distance and the second distance such that a circumference along the first and second walls (110, 120) and the first and second side elements (112, 122) shrinks monotonically with lowering said at least one distance; a first outer wall and a second outer wall being arranged oppositely to each other; a first outer side wall and a second outer side wall being arranged opposite to each other and combined with the first and second outer wall (210, 220) to form a molding there-between, wherein the outer side wall has further projections extending from the bottom part to a top of the first outer side wall, and the second outer side wall comprises further grooves extending from the bottom part to the top of the second outer side wall, wherein the further projections and the further grooves are configured to cast grooves and projections at the side parts of the precast load bearing wall panel which are adapted to engage with each other when connecting the precast walls with each other; wherein the shrinkable core is arranged in the mold such that the first and second wall (110, 120) are arranged in parallel to the first and second outer wall (210, 220), wherein the shrinkable core comprises: characterized in that at least one of the first and second outer side walls (212, 222) comprise at least one protrusion which extends in the mold and is configured to get into contact with at least one of the first and second side elements (112, 122) of the shrinkable core when it is inserted in the mold such that after casting the load bearing wall panel with the cavity formed by the shrinkable core, the cavity comprises a further opening perpendicular to the two openings along the lateral extending of the shrinkable core. a shrinkable core comprising a first wall and a second wall being spaced from to each other by a first distance to define an internal region in-between; a first side element and a second side element arranged to close opposite edge portions of the spaced first wall and second wall such that fluid concrete cannot pass the opposite edge portions to get into the internal region, the first side element and second side element being spaced by a second distance; and a spacing element configured to vary at least one of the first distance and the second distance such that a circumference along the first and second walls (110, 120) and the first and second side elements (112, 122) shrinks monotonically with lowering said at least one distance; a first wall and a second wall being spaced from to each other by a first distance to define an internal region in-between; a first side element and a second side element arranged to close opposite edge portions of the spaced first wall and second wall such that fluid concrete cannot pass the opposite edge portions to get into the internal region, the first side element and second side element being spaced by a second distance; and a spacing element configured to vary at least one of the first distance and the second distance such that a circumference along the first and second walls (110, 120) and the first and second side elements (112, 122) shrinks monotonically with lowering said at least one distance; a first outer wall and a second outer wall being arranged oppositely to each other; a first outer side wall and a second outer side wall being arranged opposite to each other and combined with the first and second outer wall (210, 220) to form a molding there-between, wherein the outer side wall has further projections extending from the bottom part to a top of the first outer side wall, and the second outer side wall comprises further grooves extending from the bottom part to the top of the second outer side wall, wherein the further projections and the further grooves are configured to cast grooves and projections at the side parts of the precast load bearing wall panel which are adapted to engage with each other when connecting the precast walls with each other; wherein the shrinkable core is arranged in the mold such that the first and second wall (110, 120) are arranged in parallel to the first and second outer wall (210, 220), wherein the shrinkable core comprises: