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Saving Sustainably: Building a Spiral Stair

A site-built spiral staircase saves valuable floor area, but poses some construction challenges

Treads ready for assembly. The site-built circular staircase saves valuable floor space in the house. All photos courtesy Matt Bath.

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.

This drawing shows minimum tread dimensions.

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.

Spacers and treads are in roughly the right position.

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.

Pieces of scrap taped in place keep the balusters plumb.

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 form for the handrail is made from scrap plywood cut to a curve and small, square blocks on the outside of the form.

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.

Getting all of the plies for the handrail into the form wasn’t easy.

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.

Sanding alone turned the rough blank on the left into the finished handrail on the right.

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.

The top of the staircase is finished with a wooden newel.

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.

Previous posts by Matt Bath:

An Introduction

Foundation Formwork

Designing and Installing a Septic System

Pouring the Slab

Framing the First Floor

Framing the Second Floor

Framing the Roof

Shingling the Roof

Wall Sheathing

Installing Drains and Vents

Plumbing Rough-In

Completing the Dry-In

Electrical Rough-In

Installing the Ventilation System

Installing Trim and Siding

Air Sealing and Insulation

Interior Walls

Installing the Heat Pump

 

16 Comments

  1. User avater
    Armando Cobo | | #1

    I have a different perspective. Circular stairways are fine for some uses, but not for most applications. Here is a few issues I have with them:
    • On a 26” radius stair, the effective and safe walkable depth is about 14” from the edge, making it very unstable, dangerous and far more able to cause accidents for all, and especially for young kids and elderly, since the raisers are 2’’ higher than regular stairways, and usually, the spindles are further apart. Same goes for big folks. Those are the main reasons that some codes do not allow them to be used as the primary access to a full second floor of a home.
    • On my calculator, the area of a 3’x14’ straight stair, including 2-3’x3’ landings, is 60 s.f. A 5’x5’ clearance area is needed for a 56” radius circular stairway, plus 26”x36”, or 13 s.f. for landings, totals 38 s.f. I’ll sacrifice those 22 s.f. for safety and comfort anytime.
    • Only one person at a time can go up/down the circular stair.
    • It’s a lot easier and safer to move furniture up/down, or even carrying bags or boxes, on a 36” straight stair than a 26” wide circular stairway.
    • Your own picture really doesn’t show much usable space under the circular stairways, not even for storage.
    Bottom line, if circular stairways were “better” for all homes, then it would be the standard. I do love them on outdoor applications.

    1. User avater
      Michael Maines | | #2

      Armando, have you seen statistics for how many accidents actually occur on spiral stairs? I generally share your concerns, but Matt makes some good points--in particular, how much space a conventional stair requires.

    2. User avater
      Armando Cobo | | #4

      I don’t have any data, but I know of two people that had bad accidents on spiral stairs, and a Builder friend of mine, his Dad was killed on a spiral stairway. I’ve designed spiral stairs on some of my houses, every one of them outdoor and all 36” wide treads, and I’m always super careful going up/down as I’m never comfortable.
      Since you asked that question, I did a Google search. On several sites, National Safety Council is quoted that more than 12,000 people die every year in the US from stair accidents , and the biggest culprit is loss of balance. See my comment on safe walkable space on a tread. “Statistics from the National Safety Council show that Americans over the age of 65 are more prone to fatal injuries from falling down stairs”, “and the most common injury is a broken hip, and 30 percent die from these accidents”. (I didn’t looked the stats, just read the article)(Hey, it was on the internet, so it must be true)
      Attached is an interesting slide picture from a survey in New Zealand about safety on stairs. The study is way too long, but you get the point. (again, from the internet)

      1. Malcolm Taylor | | #7

        I agree. You aren't helping a senior or anyone with a disability down a flight of circular stairs, and would be insane to carry a baby or even a load of laundry on one. They are for the fit and able, essentially limiting access to the second floor for many people.

    3. John Clark | | #8

      Agree 100 percent. Spirals should stay dead with the 1970's-80's.

      I suspect the OP will change his tune after having busted his @ss on those stairs while wearing socks.

  2. Peter L | | #3

    How do you carry something large up a spiral staircase? Like a sofa, king bed mattress or a large flat screen TV?

  3. Malcolm Taylor | | #5

    Our latest code revision effectively made all spiral stairs here illegal.

    I think it's mistake to for some reason look at stairs as just taking up space unnecessarily. We don't do the with any other element of the house, and traditionally stairs were something you celebrated and made into features. Put bookshelves along one side, make the landing into as small sitting nook. No reason to write them off.

    The design Matt chose, which makes each tread a giant cantilever with very little meat on the other side of the centre pole - especially when made of spruce, - gives me the willies.

  4. Alan Afsari | | #6

    Aesthetically, I used to love spiral staircases. Several years ago I chose an apartment to rent that had a spiral staircase to a loft bedroom. That year I hit my head on the stairs so many times that I decided I would never live with a spiral staircase again.

    As far as the question, How does one get large pieces of furniture up the stairs? A lot of cursing.

  5. But Why? | | #9

    The only thing to say about circular stairs is
    Groovy Baby.

  6. Trevor Lambert | | #10

    I'll pile on and say that this spiral staircase is a bad idea. The pros are minimal - slight savings of floor space, they look cool. Functionally, they are terrible. The effective width of the stair tread is a lot worse than it first appears. With a straight 36" staircase you lose about 3" off each side for the railing, leaving you 30". With this 26" spiral, you lose at least 12" off one side and 3" off the other side, and even at this you're left with a rather tiny 7.5" tread depth on the inside (a standard stair is at least 9" by code, and up to 11" is not uncommon). So you've got about 11" of effective tread width left; combine that with the fact you're going around a sharp corner the whole time, you're pretty much required to place each step in an exact spot of each stair +/- an inch or so. That's going to get old really fast. Have fun calling out to make sure no one else is coming up or down the stairs at the other end before beginning your journey up the stairs. I wouldn't consider carrying even a modest sized box on those stairs.

  7. Kevin Dickson, MSME | | #11

    Alternating tread, or Lapeyre stair, might be safer, and takes up less space.
    Codes don't generally allow it in residential construction, but it's a smarter alternative to a spiral in many applications. Commonly found on ships.
    Winding stairways are allowed in the US, they are very common in Europe, and save a lot of space as well. https://www.bobvila.com/articles/how-to-build-a-winding-staircase/

    1. User avater
      Jon R | | #12

      Had to look up Lapeyre stair. Evidently it can be steeper while still going down it facing forward.

      https://d3pcsg2wjq9izr.cloudfront.net/files/7744/images/1-40.jpg

  8. Vivian Girard | | #13

    As a spiral staircase enthusiast, I quite enjoyed that piece.

    A dozen years ago, my wife and I were able to turn the basement space of our first-floor condo into a quite pleasant living space. A small spiral staircase was a key to make it all happen. I wasn’t too sure about how it was going to turn, but it worked out beyond our expectations. As pointed in Matt’s piece, when well situated a spiral staircase can be a huge space saver. In our situation, we have a regular staircase going from floor to floor in the common area of our building, so moving large stuff is not an issue. This allowed us to use a 3’6” staircase as opposed to the more standard 60”. The required floor opening of a 3'6" is only 46”by 46”. I can say that this improvement in space use and efficiency was life changing. In our expensive City (Boston) it allows my wife and I to have a nice-enough-for-us home with a good amount of privacy while still enjoying the occasional company (and steady rent!) of a couple of stable housemates. While their rents remain well below market rate, our lodger's financial contribution is what allowed us to repay our mortgage quickly. Nowadays it more than covers our housing expenses. This in turns means that we can focus our time and energy doing things that we enjoy and value (including writing semi-annoying comments!) as opposed to spending our days working for the man.

    From an environmental perspective, the ability to safely and comfortably house more people under the same roof is much preferable to building a new things, even if it's housing covered in PV panels.

    Here are some additional observation based on my experience:

    - Unless I am carrying a large item, I find a smaller staircase easier to navigate than a larger one as it is easier to use hands on both sides when going up or down. Anyone under 225 lbs who doesn’t struggle through a regular staircase should have no problem navigating safely a narrow spiral staircase. Not rushing and using one’s hands are the keys to safety when going up or down, but that’s true with any stairs, not just the spiral type. As with many other things, after a little practice, say, a couple of weeks of regular use, a spiral staircase can feel as natural as a regular one.

    - While I am impressed with Matt’s decisions to build his own spiral without previous experience, a good alternative is to look for one that comes as a kit. Those can even be found used and perfectly reusable since there are no mechanical parts to break. If Craigslist is a thing where you live (there are more listings in large metropolitan areas) they can also be found there. It can take some patience and a bit of compromise in the layout, but that’s how I found a spiral staircase kit for $500 at a building reuse center. I posted below the link to one such good Craiglsist listing at the time I am writing this. If buying a kit, used or new, be mindful of which way the railing turns.

    - A spiral staircase kit is relatively easy to assemble, disassemble transport and store. I carried mine inside a Toyota Echo (with the railing strapped on top). That also makes it highly reusable in a new project.

    - Splurge a little, especially if the staircase is going to be conspicuous and used daily. The cheaper kits (under $1000 new) are made of light gauge metal, and the sectional railing (a key element) feels flimsy. The better ones start around $2000 to $2500 new. The used one I found was made by Mylen (see link at the end). New it would probably cost in the $2500 -$3000k range. Even if buying new in that price range, it's still cheaper than any labor intensive finished-in-place staircase, and the amount of space saved can be worth a whole lot more.

    Useful links

    https://capecod.craigslist.org/mat/d/south-yarmouth-spiral-staircase/7122644692.html

    https://www.mylenstairs.com/spiral-stairs/prefab-indoor-kits/

    Pictures description: This 4’ by 9’ space would have been barely large enough to fit in a regular staircase with landings and a small closet. Thanks to this 3’6” spiral, we were able to fit a (nicer looking IMO) staircase, my home-office on the upper floor and our favorite love seat at the lower level. All of this came at considerably less expenses than it would have cost to build a regular staircase. Navigating a spiral staircase is not hard or dangerous for most people; just be mindful, walk on the outside edge and use your hands. Spiral staircases can be a magic improvement for a smaller and -inherently greener- home!

  9. User avater
    Armando Cobo | | #14

    Getting used to an unsafe stair type is one thing, circular stairs being safe to become the standard or code approved, its another. These people also got used to their stair... ;-)))
    https://www.cnn.com/2020/05/15/asia/china-cliff-top-village-relocation-intl-hnk-scli/index.html

    1. Eric Habegger | | #15

      Wow! It sort of reminds me of how parents used to tell their children to eat all their food because children in China would love to have that much food. Of course this way of thinking is all outdated as China is emerging from their dark ages to challenge us in every way. I imagine they are now telling their children to enjoy their wide, straight, safe stairways because people in America are now going backwards and installing unsafe spiral staircases in order to economize on space...

    2. Eric Habegger | | #16

      I just realized how the "Wow" looked. It wasn't referring to a shortcoming of Armando's comment. It referred to the amazing climb those Chinese children went through. I didn't realize till just now that it might look like I was projecting that Armando was looking at the Chinese as backwards by my saying "wow". I know he wasn't.

      I was just being cute with the second part of that comment and didn't realize how the combination of sentences might have come off as glib and looking down on Armando. Sorry.

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