I have a partial basement under my house, in this area, the 2"x6" joist are spaced 16" centers with the area being 17.5'x17.5'.
I'm considering placing a cross support, perpendicular to the joist run, of 4"x3"x.250" rectangular tubing, supported at each end. I recognize the level of flex as a load increases. Have considered placing 2 tubes side by side, welded together as one, to run the span. This would create a 4"x6" support with a 4" drop from the joist.
How much would this increase the resistance to flex and would the welds need to be continuous the full length of the beam or could it be a 6" weld spaced 6" between welds, top and bottom with welds offset of the gaps.
I wish to set up a king size water bed in the room above.