Is a 6X6 IBeam enough to support the first floor of a house?

Question

I need to add a support to the ceiling in the basement of a house. The span I need to cover is 19 feet. Would a 6X6 steel i-beam do the trick?

Answer 1

Yes and then some! A better question is do you have a small army formed to get said I beam into the basement!? lol

Answer 2

19 feet is a fairly long span for a 6 inch deep beam of any material, even if you don't exceed the allowable stress in a steel beam, deflection is likely to be a problem.

While you did give the span, that is not enough information to give an answer, you also need to know how much weight is being supported.

[EDIT] the additional details help. If the 26ft direction is being divided into 4 equal spans, then each beam supports 1/4 of the total area (the end walls support  the remaining 1/4) so you have 6.5' x 19' about 124square feet of floor on each beam. A typical live floor load for a residence is 40 lb/ft^ the dead load (weight of the floor structure itself) can vary depending on construction and floor covering, but 20lb/ft^2 is probably pretty conservative. (40+20) x 124 = about 7500lb uniformly distributed on the beam, which I'll assume is simply supported at the ends. Looking at the tables in the AISC, ASD 9ed.  We see that the tables only go up to a 14ft span for any  W6 beam, As I said before, 19ft is a lot for a 6" deep beam. Just because it is not in the table doesn't' necessarily mean it won't work, for example at 14' span a W6x25 could support more than twice your load, but I don't really want to bother doing the calculations because I really think the deflection is going to be excessive.

An W8x? would probably work, but you need to get a licensed engineer to calculate which weight. The tables show that even for a  W8x13 (pounds per foot) the allowable stress would not be exceeded, but the deflection would be too high. A heavier beam will be needed to reduce deflection, but it will take some calculation to determine which, it can't just be simply read off a table.

The above assumes the new beams will carry all the load, usually when people ask this sort of thing they want to remove existing supports to open up the area. If you are going to keep the existing structure and just reinforce it, you will probably need less steel, but clearer information about the existing structure, and more calculations will be needed, so you really need to consult a local engineer.