Just purchased a 1950's ex council house that has a single skin wall side extension, only 1 storey and a flat roof Not of sure the material of roof but hopefully not asbestos. But basically i want to knock out a internal wall to make it longer. How should I go about this, do i need to put a lintel in? If i do i was just going to mimic the same setup as the lintel already in room, build a column up where the wall is then put lintel across and remove wall. Ive done my research and know the type & size of lintel i need. When installing a lintel do i need to wedge it up against the roof or just making it a tight fit suffice? Ive probably explained this really bad, so apologies in advance.