Hello, I want to open up an exterior load bearing wall for a room addition. This is an 2'' x4'' first story wall with a basement underneath and another story above. I live in north central Ohio so it would need to accomodate snow load as well. I want to span 20'. Can anyone help me figure out the beam size and # needed? thanks

I removed the carpet in my upstairs bedroom and am looking to replace it with laminate. I have checked how flat the subfloor is and noticed a couple of dips. Both dips are on opposite walls about 1 1/2 feet in. Over the span of 5 feet from the wall to 5 feet into the room, I measure about a 1/4" dip. This is true for both dips. I'm concerned laying the laminate on these dips may cause issues. What exactly do I use for this? I've seen SLC elswhere on this site, which I assume is self-leveling compound. I can purchase this - however, do I need to worry about it leaking through any small cracks in the plywood (by cracks, I mean the gap between two plywood pieces)? Also, one other question. Some of the plywood boards don't line up evenly with one another, but they are less than 1/8" off.. Do I need to worry about this? Should I focus on sanding them? If so, what is recommended for smoothing this out? Thanks!