How do I calculate the size Beam I need to install Bi fold doors.Openining is 5.5 metres wide and 2.4 metres high. It does not support a tiled roof, just a colourbond roof. Can any one help please.
OK, you gotta be overseas, I don't work in metric too often. Sizing a beam is identical the world over. You need to know the loads that the beam will support, which is a function of the geometry (clear span) and unit loading of everything above the beam (live plus dead load with appropriate factors of safety). You generally get the loading from code if you are doing residential or light commercial. Then either you get the beam size from standard tables, IF THEY APPLY, or you use principles of mechanics to compute the required beam size.
Beam size depends on the load (as discussed), and the material properties of the beam. A sawn lumber beam is going to be a different size than a steel beam, which is going to be different than a glue laminated beam, etc. The span you quote is relatively large, so you are looking at a fairly large beam. But it cannot be sized over the internet due to the need for detailed, accurate knowledge of your specific code requirements, and accurate knowledge of the geometry of your building. Sometimes (I know this is a radical idea for a DIY forum) people actually HIRE professional engineers or architects to size the beam for them, especially if the geometry is complicated, the loads are large, or they have no idea how to do it themselves. Sometimes you can bring a sketch to a lumberyard, and the yard will size the beam and include the cost with the Glulam they sell you.