Is a spiral staircase actually practical for daily use?

We've had one for about six years now, main stair from kitchen to bedrooms, so I can give you the honest version. Laundry basket: you learn to carry it on your hip like a toddler, becuase both hands go on the rail. Groceries are fine one bag at a time, annoying with eight. Kid on the hip is the one that gets old, honestly. Three steps up you realize your hand is full and there's nothing to grab. My wife just planched the kid in a carrier until he was two. Furniture is the real dealbreaker, a decent mattress went up through a window on a couple of straps. Day to day you adapt faster than you'd think, but if this is your only stair, live with that tradeoff before you order.

On the headroom, don't trust the catalog drawing, check it yourself. The number you need is the distance from the walking line of the stair up to the floor edge above, and the tight spot is always where a tread passes under the front lip of the opening, not the center of it. Get the riser height off the spec sheet, count how many risers it takes to climb from the bottom tread to where your head would hit the floor edge, and measure what's actually there in the rough opening with a tape and a plumb bob. If it's tight on paper, it'll be worse in real life once treads and finish flooring eat up an inch here and there. Ten minutes with a tape measure beats a phone call to the stair company after the steel shows up.

For attachment, ours has a base plate that bolts down to the slab with wedge anchors, and up top a bracket that screws into the framing around the landing. The center post does carry most of it, so the slab spot matters. Tap around where the plate will sit with a hammer, a hollow sound means thinner pour or voids underneath. If you want certainty, have the builder drill one small test hole and check the depth. Also confirm the slab there has no radiant tubing or rebar in a bad spot before anyone fires anchor bolts into it.

Worth a call to your building department before you commit. Ours wouldn't sign off on a spiral as the only stair to a bedroom floor, somthing about width and riser rules for egress, so we wound up doing a tight winder stair instead and it scratches the same itch. Takes a bit more floor than you're hoping for, but we can haul a queen mattress up it and I've never once had to strap furniture to a window. Also check what your insurer thinks if it's your only way up. Cheaper to ask now than after the hole's cut.

Put your hand on the catalog and look at the tread dimensions, not the overall diameter. Ours is 5 foot across and the usable part of each tread is only about 26 inches deep at the walking line, the inner half is basicly decorative. Anyone with size 12 feet learns to walk on the outer edge real quick. Also think about wich way it winds before you lock in the landing spot. Ours turns so you step off facing the hallway, and that ended up mattering more than I expected. A friend's spins the other way and you come off the top facing a wall, so everyone exits sideways every single day.

Put one in a lake cottage back in the late 80s, steel kit job. Two things the catalog never tells you. That center post is a big chunk of steel running floor to floor, and in winter it drinks the cold right off the slab and chills the whole room. Ours sweated in humid weather too. And after twenty years the bolt holes at the base plate elongated a little from the post flexing every time somebody went up. Used to snug the anchors every spring like clockwork. Ask the manufacturer what they say about retightening and how the post is isolated from the concrete. Ours sat right on bare steel and I'd do it different now.