I am trying to fit upvc slide door in between the door and the boarded window, see pic. the width of the door will be 2100mm. Hence, I need to brick up half of the door and half of the boarded window to make the required space for the door. is there any way I can do that without taking the two concrete lintels which are on top of the window and the door? they are solid concrete lintels and span over the two skins of the walls.