Call an architect or a designing building contractor.

You will need to add a header and header support columns. Figuring the loads and sizes is a job for an experienced professional with insurance.

This is a project in which you should consult a professional. However I have a few questions.... Are your ceiling joits continuous or do they break on the wall that is being removed? What is under these rooms living space, crawl space or a slab?

Hire a structural engineer who will put his stamp on the plans.

We removed a load-bearing wall and replaced it with a flush laminated beam in the attic above (look ma, all open space!). The other (simpler) option is to have posts on the side and a beam below the ceiling, all of which will be covered by drywall. You need to decide which way you want to go.

We went to a truss company that built us a lam beam, and did the calcs for how thick it needed to be, based on how long the span was. One end rested on the rim joist and the other on a LB wall, so the loads transferred properly. We then followed the directions in a really detailed article in Fine Homebuilding that someone on GW pointed us to (cut into existing attic joists, put beam between them, attach joists to new beam with joist hangers). If you're interested in going that way, and you trust your DIY skills, let me know and I can give you more details.

With the inside-the-room option, you still need to get the right size beam and ensure the posts/columns on the outside are transferring their load properly. Hence the above questions about what's under the floor.

Replacing a load bearing wall with a beam really is not all that tricky. Of course first thing is get a structural engineer to determine the size of the beam. A lot of people want to skip the part where you put up temporary walls to hold up the ceiling while you are installing the beam, not a good idea. I had one guy get all bent out of shape when I told him that he should not have used short sheet rock screws to fasten the joist hangers.

Thanks for the input, everyone.

I am thinking of going the 'ceiling-beam-secured-to-sidewall-posts' route (and finish off with drywall). I figured there's a calculation related to the length of the opening and the expanse being loaded (attic/roof), by which I can determine the proper size beam.

The floor joists lie perpendicular to the wall length I'm removing. The rooms sit above a 3' crawl space. Perhaps I would need to reinforce the floor joists with support beams? If so, do ALL the involved joists need to be supported where the wall is being removed?

The attic joists also run perpendicular and, indeed, they DO meet at the point of the wall in question.

Input & insight? Thanks.

Go down in the crawl space and see what's underneath the LB wall. If there's a beam underneath the existing wall, you're home free and a couple sidewall posts that rest on that beam will transfer the load just fine.

As far as temporary support walls, they'll only be up a short period, and in that time you're not likely to get a bowed floor (that's generally something that happens gradually over a period of time), so you don't need to do any extra reinforcing in the crawl space.

For a 16-foot span, I'd go with something engineered for the beam. Call up a local truss company and they should be able to help you with the span calcs. Our laminated beam was over 20 feet long and cost less than $150.

Linked some pics below of our LB wall removal.

Here is a link that might be useful: wall removal

Draw a scaled plan and a section with accurate dimensions and people can tell you something more definite. Everything depends on the ceiling height, span, load supported, available support points below the floor, etc. There are no simple answers that apply to all possible conditions although if the 16 ft dimension is perpendicular to the attic joists/rafter ties, then a beam above the ceiling will work if there are adequate support points at the ends. The load of the attic joists depends on whether or not the attic space is large enough to be used for storage or future occupancy.

Weedyacres, do you remember the title of the Fine Homebuilding article detailing the work?

I might have a copy of it on my home computer. I'll look it up when I get home Friday. Nudge me again if I forget.