I am changing my 2 single garage doors to 1 16 foot gliderol roller door.
I know i need to support the roof (flat roof) whilst i take out the middle pillar and i will also need to replace the wooden lintl resting on the middle pillar.
As it is only a flat roof above i was intending on replacing this with a steel rsj. i was originally looking at 6" by 3.5" rsj 5.4 metres long but will this sag under its own weight. it is only supporting a flat roof with felt so not massive load bearing. if i go for a 6" by 6" steel rsj will this be enough or do i go bigger just for safety.
Cheers in advance