Hello i am looking for information on what size is steal beams i should put into cavity wall there is 3 meter opening on a corner , i was thinking to put 2 beams 100mmx200mm of a 3 meters . But not 100% sure if that is sufficient . I have plans attached . There is currently extension build already with doors but want to open all the way it is the door way from dining room to family room on the plans ( kitchen , dining room , utility room is 1 store extension . everything else is two store house .
P.S floor joist do not sit on the walls that being removed there is another beam already installed dividing family room into half and floor joist sits on it
Another question i have is do beams have to be on the same level or can one be higher other is lower ( i dont see reason why not but prefer to double check on other opinions ) .
And last question is how do you sort out DPM in this instance as well as cavity gap between beams .
This is more informative sample ( the walls that being removed is archway )