spans larger then 16' can easily be accomplished. Your trade off is obviously a deeper floor system or a heavier type of construction. Spans greater then 16' can easily be done with a heavier 11 7/8" i joist or a 14" i joist. You can also use a floor truss, but chances are they are will 14" range. A 14" i joist would be cheaper then a heavier 11 7/8", both of which are cheaper then a truss. You can also go with a smaller member and space them closer together (16" or 19.2"). Many options. My advice is to make the plan, and it usually can be engineered without much sacrifices.

Thanks for the feedback everyone! A little more information, we live in the San Francisco Bay Area, and the local building department allows us to only have an engineers stamp, it isn't required to have an architect. Additionally, our builder (while not an architect) has a lot of experience drawing up plans, and if we could find a floor plan that only needed some modification then he could draw up the plans. Maybe we will end up going to an architect after all, however at the moment I'm just trying to collect some floor plan options to see if we can avoid it. Ideally, we are looking for a single story home that has a large great room, windows in the kitchen, 3-4 bedrooms and about 3000 square feet. We don't need a seperate dining room, or formal living room, though if a plan has a dining room we will turn it into an office, or some sort of other "flex" space. Thanks!!

I had exactly the same problem. I do not know how it is done for you, but we have two layers of subfloor and, when we will renovate the kitchen in a couple years, we will fix the subfloor and put either wood or tile that will be flush with the rest of the floor.. We have a transition between the two levels, so it was not as weird as it look on your picture. Sorry for the mess, but it was just after we moved in. May be you can do something like that.

I feel like this is a family room type look. But you can use as dining room if that works better for you Many will ask for more pictures and a floor plan. So if you can post those. But I guess to answer your question, if you do end up using this as a dining room: There’s not much room for much so a rug, table, chairs, maybe a bench on one side, what’s your style? Maybe wallpaper on the walls.