Hi I want to widen my fireplace by appx 1ft each side and 3 courses up (i am going to put a lintel in here) - how do i support the internal chamber. I know i can use strong boys to support the face and sides whilst i put in the lintel but do i need to support the inner chamber just behind the face on the left and right of opening because i will be removing bricks from here??. all replies appreciated. 
