One approach other than replacing the supporting beam is to make the
"supporting wall" self supporting, not only of itself but the load above
it. Most generally stated, remove the plaster wall boards and replace with
plywood and bracing. And calculate the deflection and then hold the load
hi an equivilent amount so the supporting wall, ie beam wall, doesn't sag
with the load. In other words, give the "beam wall" a little upward
curvature to compensate for the load when applied.
There is a bit of calculation required and if you are asking the
internet about such things, your task becomes a search for someone
familiar the stresses involved; maybe an architect's engineer or one of
the companies that make roof truses for houses.
If you want to stick with the I beam, start looking for dimensions of
the current beam and, with a beam calculator (probably found on the
internet with the name "beam"), figure it's capability and then find an
appropriate I beam to match it.
There are lots of people here that have suitable calculators and would
be glad to help, given those dimensions.

Hul


wrote:
I need a smaller I-Beam in the basement of my house. The I-Beam would go where supporting joists are currently. Reason for this = if it works it will give me the allowable head room to redo my stairs. The thickest/ tallest I could allow would be 4 inches vertically and up to 2 feet 2 inches wide. This would then be a part of a load bearing wall. So I need to know how much weight that this possible I-Beam could hold. Any help is wonderfully taken into account and thank you so much in advance.