In message , TheScullster
writes
Put the beam under the rafters ..............


Do you mean joists??

Yes.


Do you actually need a beam, if there is no load on the joists?

I certainly need something. There is a wall running across the room at the
point where I intend to install the beam. At this point the joists are cut
and overlapped with the overlap sat on top if the wall, presumably to keep
the beam span and therefore the section size down. The joist spans are
approx 3.5m and 1.5m.

I suppose you could look and see if they are nailed together or jointed
in some other way.

My active brain cell was struggling with how you are going to insert
both sets of joist ends into the beam webs. I suppose you would have to
support the ceilings and slide it across.

You really must get some proper advice before embarking on this project.

regards
--
Tim Lamb