Hello.
I am planning to open up between the kitchen/dining room as it is just a regular doorway now (no frame). So I thought I would widen it by removing a bit of wall on each side of the door so the opening becomes about 2.5 meters wide instead of the current 90 cm. And continue the floor from the dining room into the kitchen. But if you cut the interior wall in line with the floorboard, there will be a sort of hollow in the wall down to the beam that rests on the concrete with sand on each side of the wall! I assume there's no sand inside the wall under the floorboard level anyway... do you need to fill/cast in that hollow or is it enough to insert a horizontal beam that aligns with the finished level of the upper edge of the board and continue with the laminate flooring into the kitchen?