I have a 1970's dormer bungerlow.I want to take one of the internal doors and replace it with double doors to let in more light.It is a load bearing wall supporting the dormers above. So i will need to replace the lintel above the door with a bigger one.To install a new lintel will i need to acroprop the wall.The only reason i question it is the house is very solidly built with block and granite sand and i only want to install a 4 ft lintell and their is not an excessive weight above as there is only 2 blocks above the lintel then obviously the floor joists for the dormers.Some sdvise would be gratefully received.