I have a 13' deep by 17' wide lean-to unheated enclosed patio. I would like to rebuild the outside walls. The load bearing wall is only 78 inches tall. I am putting in two 6' windows. I need headers of two 2X10s. Can I use steel I-beams of a lot smaller size for the job? Could I use on a 2X6 wall three 2X6s instead? I am trying to keep the header as small as possible to maintain window height. I was even thinking three 2X6s with a steel angle iron inserted for extra strength. Thanks I would really appreciate any suggestions. I have researched this and checked the charts but I am afraid I can't make sense of them. Thanks Carol
OK, you're looking at a header span of 6'-7(6'4 for the window and 1-1/2" at each end for a jack). You're carrying 6'-6(half of the 13'-0) in roof load(plus the overhang which you didn't mention) so let's say a tributary of 8'. You also didn't mention the pitch,whether the ceiling is attached to the roof or the roofing material. Since you're in Canada I'm assuming there's a snow load but I don't know what your local conditions are so I'm shooting in the dark....
My beam calc program says: for the above span/tributaries and a 25 lb/sft snow load plus a 15 lb/sft dead load(the weight of the materials used in the assembly) your triple 2x6 in #2 Spruce/Pine/Fir(whitewood) won't go. If you can source Southern Yellow Pine it works with a double, with a max deflection of .206". If I bump snow load up to 40 lb/sft, it requires a double 2x8 SYP header. If I plug in an LVL, 2- 5-1/2" LVL's work for either load very well, much better than the SYP.
Pine 2x6's or LVL's are a lot cheaper than steel beams but you might get by with an even smaller beam and that's obviously a consideration, so it's up to you to decide. I'm sure there's a local steel yard you can get to and they should be able to spec out a beam for you.
If you want, PM me with an email addy and some details and I'll help you with this.