Hi I want to install a dormer window into our bedroom there is already a dormer in the bedroom next door. I have been in contact with building control and they state that no planning is needed just inspection during the process. There is no rsj to support the weight of the dormer so do I need to double up the rafters either side of the dormer and then transfer the weight from the top chord and bottom chord of the rafters I am going to cut with cross beams? the length of the dormer will be aprox 3 metres