Cantilevered deck with nothing under it - normal or sketchy?

I prefer the aesthetic of the floating design, provided the structural work behind it is absolutely top-tier. I actually oversaw a build last summer where we wanted a massive cantilevered area over a covered patio, so we decided to go that way. The biggest mistake people make is thinking it is simple framing; it is not. It is a serious structural engineering decision.

For that project, we couldn't use simple joist hangers for the entire span. We had to integrate heavy steel moment connections right into the main house wall framing. Essentially, the load was being transferred back into the foundation of the house itself, not into some small, discreet footing just for the deck. We were using 2x10 ledger boards tied into the structural studs using custom galvanized hardware to handle the shear forces.

If you are building over a substantial, solid wall—like an existing garage—you are in luck, because you are attaching it to a proven load path. If it is just a freestanding house, you need to calculate the proper bending moment for the distance you are extending. Just going six feet out is much easier than extending ten feet. It just means you have to engineer the connection point much more robustly.

I have mixed feelings about the floating design approach, expecially when it comes to complicated terrain. I worked on a job outside of Seattle where a client wanted a dramatic ten-foot extension off the back wall. The initial idea was to do a full cantilever, but the guy checking the plans told us the soil shear on that specific hill was too unstable for that amount of unsupported weight. It wasn't just about looks; it was about how the pressure would translate into the ground. We ended up modifying the design to add hidden support points along the outer edge, essentially creating a deep ledger connection into the foundation below. That way, the structure still looks very clean from above, but the critical loads are handled by discrete points rather than relying solely on the main house attachment. I think relying on sheer strength from the main structure is always a risk if you don't have the perfect foundation conditions.

For me, the peace of mind of knowing there is a robust system of support, even if it's hidden, is more valuable than that pure aesthetic appeal. It makes the whole building feel safer.

We wanted the same floating look on our place but the ground made the call for us. Back yard drops off fast and the top few feet is loose fill, so hanging the deck off the wall was never in the cards. The thing that saved it was helical piles. They screw down deep past the junk soil and gave us posts that hold without tearing up the whole slope. From the yard it still looks like it hovers, you only see the posts if you walk around below. So on the original question, I'd ask what the soil is doing on that hillside before deciding anything.

The line between a few feet and ten feet is pretty much written into the code tables, at least around here. When I rebuilt my own deck two years ago the inspector made me keep the joist overhang at 16 inches past the beam, and that was with pressure treated 2x8s on a simple layout. Anything past that and you're into span calcs. As for what I'd pick, honestly the posts win for me. I've crawled under too many of these things to trust anything I can't see holding up.

We bought a place with one of those no-post decks a few years back and nobody warned me about the maintenance side. Since there's nothing below, the whole underside is exposed, so you've got two surfaces weathering at once. Water drips off the upper level right onto the lower one too. I've spent more weekends on my back under that thing staining joists than I ever want to repeat. Looks great in photos though, I'll give it that.