I installed a spiral staircase in my small house, with the help of a carpenter. It was a task that took about 3 days, including the prep work. Spiral stairs are a fairly straightforward project, with some of the usual frustrations of working with any building product.
I ordered a spiral staircase kit from Salter Spiral Stairs, and it cost about $2300. It's steel, with an aluminum handrail. I got the 5'6" diameter size, which is comfortably wide. The design meets the building code.
It took a few weeks for Salter to manufacture the stairs and ship them. They didn't call to tell me that it had shipped, but luckily I called them to check on progress before it was delivered to my home. It all came in one huge heavy box, except for the center pole and the pre-formed handrail. I broke open the box to move it all into the house.
The first step in installing the spiral stairs is to stand up the pole and slide the treads onto it. Then attach the platform at the top over the pole and screw it to the wall. Support flanges under the platform interfered with putting screws through the pre-drilled holes, so we had to drill new holes.
Next we got the center pole plumb and screwed down the base. By attaching the platform first, it determines the exact location of the pole. Then we attached a baluster to the top tread, slid it up the pole and fixed it in place with set screws. That's right -- you work from the top down!
A baluster connects one tread to the next and locates it around the spiral of the stairs. The pieces are heavy so this is definitely a two-person job.
After all the treads are in place you attach the handrail. The curved rail takes up a lot of space and I had to corkscrew it into the house and up the stairwell. Again working from the top, drill a hole up through the baluster and attach the handrail with a screw.
Handrail all attached? You're not done yet. Now you have to cut all the intermediary balusters to length and screw them into place. 33 of them in my case. Then cut off the extra handrail and plug the end-hole.
I didn't paint my spiral staircase, although that's actually "step one" in the instructions. The parts are primed with a black primer and look fine. When the treads begin to show wear I'll either paint them or cover with wood treads.
My spiral staircase kit from Salter Industries is a well-made product for the most part. Installation is not as easy as they make it out to be, and the instructions could definitely be improved with more detail and tips. As with all building products, you're the last person on the assembly line so expect to do some cutting and drilling of steel.