Load bearing capacity of RSJ's

Hi Martin The two smaller beams will undoubtedly be the outcome as the weight of the single beam would be approximately 350kg this would cause issues on installation especially with a beam of this weight with regard to health and safety issues.this may be more costly as the beams would have to be bolted together a 600mm centres with m 12 bolts,you should also be incorporating steel column supports at either end and a ground beam encased in reinforced concrete at threshold level if this for the application of patio or bifold doors etc,do not just rely on beams as lintels for this application regards dale

you will have to do the relevant calculation to define the load that will be placed on the beam this will define the beam size you need, you must also remember the associated structural details like the packing and shimming of beams, the pad stone support required to the ends of the beams and any foundation work required under the wall supporting your beam. try the Steel Calculator https://www.steelbeamcalculator.co.uk but you might be better just asking your Architect or structural engineer. Good luck with your Project