I think my fascination with spiral staircases stems from my love of efficiency.
With a standard staircase, there is a ton of wasted space on both floors. For example, with 8-foot-tall walls, the steepest straight staircase allowable by building code in my area would have a footprint of just over 12-feet-long on the second floor and well over 14 feet on the first floor. At a width of 3 feet, this is a total area of about 80 square feet, including landings.
Most architects use some of that space under the stairs for storage, but it still isn’t very useful. A spiral staircase, on the other hand, requires a minimum footprint of 58 square feet including landings. When it comes to saving sustainably, a smaller footprint means spending less money on a bigger house, and using less resources to build. In addition, a spiral staircase is beautiful, and I knew it would be a focal point for the house.
You can buy kits to build a spiral staircase online, but they are extremely pricey, so I decided to build mine myself. I bought the plans from Jim Self. I found his website back when I was designing the house and was impressed by the number of people who had used his plans and sent in pictures of their finished staircases. They looked really good, and many of his customers said that the plans were easy to follow. While I wouldn’t quite agree that they were “easy” to follow, they certainly weren’t too difficult, and the end result was a staircase I can be proud of.
Most of the difficulties I had with construction stemmed from a lack of high-quality tools. These stairs are best constructed in a woodshop with a joiner, surface planer, drill press, and plenty of working space. I didn’t have any of those, and I made do with my tablesaw and hand tools.
If I had any more space to store large tools, I would have bought a few and it would have made the job much easier, but I need to finish building the house before I start building my woodshop! I’ve mentioned it before, but I’ll say it again, and keep in mind this is coming from someone who doesn’t like to spend money. If there is a tool out there that can make the job easier for you, my advice is to buy it. The money you spend will be well worth it.
Design comes first
The first part of building a spiral staircase is designing it. You need to decide how thick and wide you want your treads to be and how steep you want your spiral. The International Residential Code (IRC) limits the distance from the bottom of one tread to the bottom of the next (the rise) to 9 1/2 inches. The tread width is limited to 7 1/5 inches (minimum), measured at 12 inches from the center pole.
Once you decide on the tread size, you measure the distance between the first floor and the second floor and divide by your desired rise to see how many treads you need. These numbers can be adjusted a little to figure out the size of your treads and spacers. My design called for 14 treads, each 2 13/16 inches thick. with 5-inch spacers between them. This allowed for just about the perfect distance when adding in the landing.
For those planning to build your own home, I can’t tell you often enough how important proper planning is. Even with all the planning I did, I still made a ton of mistakes, and those mistakes are the reason it has taken over two years to get to this point in the build. The more you plan, the fewer mistakes you will make, and the faster you will complete your build.
Although the plans called for hardwood, I decided to cut costs and construct the treads from spruce 2×6s. I contacted someone who had used the same plans who had also used softwood and he was really happy with how they turned out, and since softwood can be bought in thicker sizes than hardwood, it would be easier for me to build the thicker treads that my wife thought would look really nice.
The first step to building the treads was to glue the 2×6s together to make 44-inch squares, each 3 inches thick. Without a jointer, I tried to make do using my table saw, but the problem there is that you are using the opposite face as a guide as you run the board through the saw so it won’t work unless one face is already perfectly flat. My solution was to attach each 2×6 to an 8-foot level and then run it through the table saw, using the level as a guide and shaving just enough off to get a straight edge. It wasn’t a perfect solution, but I was using the tools that I had.
I glued 2x6s into a two-layer, 44-inch-square piece that was 3 inches thick. I repeated the above process six more times and then carted all of the pieces to a nearby woodshop for planing. You need a really big surface planer for this task. I was able to cut two tapered treads from each of the blocks to end up with 14 treads.
I also bought a long section of 3-inch pipe, fifteen 3 1/3-inch spacers to go between the treads, and a 3-inch nipple and coupling.
Assembly starts with the center pole
I was lucky enough to have a friend with some welding experience, so after renting a welder he helped me get my skills up to speed by practicing on some scrap metal. Then I went to work on the real deal.
After assembling the main pipe, it was time to position it and, piece by piece, slide the treads and spacers onto the center pole. After all of the treads and spacers were attached I fanned them out a bit to get an idea of how the finished product would look, as shown in the photo below.
With the treads in place, it was time to attach the balusters and railing. The balusters are made from 2×2s with notches routed at one end so each baluster can be screwed to the edge of a tread. After screwing the balusters in place, I used scrap wood and masking tape to attach them all together so they were nice and straight, as the photo below shows.
Next, I cut the center of a piece of poster board out and laid it across the tops of the balusters, stretching it into a small helix. I stapled the poster board to the tops of five of the balusters and then marked out the outside of the balusters on the bottom of the poster board. I removed the poster board and laid it on the floor so I could see all the marks. Using some geometry and a bit of trial and error, I located the center and radius of the marks I had made. I subtracted half the width of the baluster from the radius I had calculated so that gave me the center of the handrail. I added half the width of the handrail to get the radius of the outer form and subtracted it to get the radius of the inner form. Once I felt like I had a good estimate of the railing radius, I set to work making a form for it.
Building the railing
The railing is constructed of seven thin plies, which I placed on edge and glued together. I used a slower-setting glue so I had time to push the plies into the forms before they set in place too much. You want them to be able to slide past each other just a little as they bend into the circular shape.
I built the forms with some scrap plywood cut into a curve for the inside, and then small square blocks for the outside of the forms, as the photo below shows.
The square blocks allow for a little bit of space to maneuver the slats into place before they are snugged up using little shims. It’s important to take care when calculating the inside and outside radii for the forms. I estimated the radius using the tops of the balusters, and I want those balusters to be centered on the bottom of the railing, so I had to do a little math to get the right radius for the inner forms and the outer forms.
The next part was incredibly difficult, and if I had to do it over again I would have used maybe 10 thinner slats instead of the seven thicker ones I used. A few of the slats ended up breaking as I was bending them into place. Fortunately, I was able to just put those in the middle and once everything was clamped together tightly the mistake was hardly noticeable.
Once the glue had dried, it was time to experience the incredible power of sandpaper. You would never dream that this ugly mishmash of sticks and glue would ever turn into such a beautiful railing, but with some perseverance and an orbital sander, it somehow did. I swear, I’m not playing any tricks on you! The only thing I did to get the before and after shots you see below was to sand.
Even though the handrail was glued up on a flat surface, it had enough flexibility after the glue dried that it could be coaxed into the helix shape required to align with the tops of the balusters.
The last step was to drill holes in the railing for the screws and then screw it onto the balusters. I used the same method as with the balusters to countersink the screws and cover them with wood plugs. The color, unfortunately, didn’t quite match the way I wanted it to. The last step was to attach two intermediate balusters between each of the main balusters. The building code dictates that a 4-inch-diameter sphere must not be able to pass through the space between any of the balusters.
The top of the spiral staircase is finished off with a wooden newel and balusters were placed all around the perimeter of the landing. Again, it is important to notch the balusters so they lock into the landing, and also to ensure a 4-inch sphere cannot pass between any of the balusters.
I used a router and some scrap pine wood to build a railing at the top of the landing and then added a couple of metal brackets to bolt the ends of the railing to the wall. If I had really planned things out well, I would have installed some extra blocking in the wall so the bracket could have been screwed into wood. Unfortunately I didn’t so I had to use drywall anchors to attach the railing to the drywall.
I used the same brackets to attach the ends of the hand railing of the spiral to the wall. This makes it just a little less wobbly when you are really pulling on it.
I finished off the spiral with several coats of clear varnish. This will protect it and also gives it a little bit of shine. I also used some black spray paint to cover up the manufacturers lettering on the steel pipe that acts as a center pole.
The only part I have left will be to install some trim where the second story flooring meets the edge of the landing, but that will have to wait until the flooring is installed. The flooring will go over the top of the landing and the trim will extend down the edge to cover the transition from wood to plywood to top tread.
This is one in a series of blogs detailing the construction of a net-zero-energy house in Point Roberts, Washington, by Matt Bath. A list of Matt’s GBA articles can be found below. You’ll find Matt’s full blog, Saving Sustainably, here. If you want to follow project costs, you can keep an eye on a budget worksheet here.
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