I need to enlarge my fireplace to inset an electric fire. The hole needs to be 56cm wide and 52cm high and 12cm deep. I have seen and heard all sorts of horror stories about chimneys collapsing, the need to put a lintel in as a support etc. As a non builder I cannot see how cutting a hole 12cm deep could cause the chimney to fall down. What is the safe way to do it? Should a lintel be put in above the hole (before the hole is enlarged). If so, how high above the top of the hole should it go?
Thanks
Brian