Building the Cob Honey House: Part 3 – The DIY Spiral Staircase

The honey house now had a green roof with a sitting deck but we had no easy way of getting up on to it. We had thought about a roof access system from early on in the build and considered incorporating floating stairs in to the back wall or building a ladder. It was always our dream, however, to build a spiral staircase and this seemed like the perfect excuse to learn how. It was a steep learning curve but we managed to build a custom spiral staircase with largely reclaimed materials. It was actually relatively straight forward, all things considered. Here’s how we did it…

First we needed a design. This is an outdoor staircase so we knew we wanted a metal frame work. We used 2.5″ schedule 40 steel pipe as the pole. Then we started modelling… Sketchup saves the day again. A couple of 2D images of my model can be seen below.  A staircase can be worked out mathematically using a daisy wheel but I cheated and used an online spiral staircase calculator that came up in a simple Google search. There are a bunch of them. I like this one. There are a few things that you need to know when building a spiral staircase.

1. The total height of the stair case from the ground  ( a.k.a. total rise)

2. The angle of rotation of the spiral (ie where does the first tread sit compared to the last when viewed superimposed on a circle from above)

3. The height of each rise, this can be no more than 9.5″ to ensure adequate head room when you pass under the landing

4. The number of treads

5. The length and width of each tread. Each tread ends up tied to the treads above and below it so leave room in your design for about 1 inch of overlap on each one.

6. Have a look at some spiral staircase building codes to get a sense of what typical dimensions are. When you start to fiddle with this you quickly realize why a 3D model is helpful.

Once the measurements of the staircase were all worked out we started building. We scrounged for metal and spotted a fallen mini-mall sign on the side of the road. The business had left the mall and the managers said we could have it. It was a great source of angle iron which we thought we could repurpose in to strong supports for our treads. We pulled out the angle grinder and started cutting.

First  everything was de-rusted. Then a 90 angle was welded together for each tread. There were already 8 corners inherent in the sign so I only had to weld up a few more. For those of you who don’t weld, but wish you did: welding, at least at a basic utilitarian level, is quite straight forward to learn. My welds aren’t pretty but they work fine. A flux core wire feed welder is reasonably affordable. A stick welder even more so. There are lots of easy to follow tutorials online. Welding opens a lot of doors in the DIY world. Maybe now’s the time to look in to it.

A cross support was added to each one for strength.

Then each tread support was welded to a section of 3″ schedule 40 pipe, cut so as to space each tread to the correct rise. The 3″ pipe fits perfectly with swivel room over the 2.5″ pipe. We drilled holes in the top of the tread supports which we would use later to bolt down the treads.

Then they were all painted up in rust paint. If you look carefully you’ll notice that one of these supports has a shorter section of pipe than all the others. That is stair #1. Its pipe is shorter because it will sit on the 3″ pipe attached to the base of the staircase, as seen below. Together these two sections of 3″ pipe sum to make a rise.

Our treads are wooden. We found these fantastic old oak door frames at our local┬áHabitat Restore for next to nothing and used them for the treads. I think I paid about $25 for both of them. They required a little work but it was worth it. Don’t be fooled by their ugliness.

We pulled off the old door frame hardware and sanded them up. Because these were door frames in their past lives they had a rabbet milled in to one side. No problem. We just filled these with some strips of common lumber, pinned and glued in to place. Then we mapped out the treads on to the boards and used a simple home made jig to cut them on the table saw. Yes, you can cut circles on a table saw, there are lots of videos online showing how to do this. It was pretty fun! You can see in the photo below how we pinned the filler strip in with the tread outline in mind. Then we went back and added a few more pins closer to the edge after it was cut. We practiced with our jig first on a prototype of ply as can be seen in a photo further down this blog. We ended up with a set of cloned treads with a perfect and consistent curve on each one. The curve on the narrow end was cut with a simple hole saw piloted through the hole from the circle cutting jig. Sadly, we were short one tread in the end so we made one out of two pieces of 3/4″ ply, good one side, glued and screwed together. Worked great.

We painted the wooden fills in pretty colours and sealed the whole thing in polyurethane. I think we might upgrade this finish to Cetol marine grade finish next season for better weather protection.

The base for the stair case was made by attaching a 3″ diameter section of pipe to a concrete footer. The pipe section was welded to a metal plate which was then painted up and bolted to the concrete.

Then the actual stair treads were bolted to the supports. To lock the spiral in to place each tread was tied to the one below and above using sections of threaded rod secured with locking washers and acorn nuts. Note that in order to do this each, tread must overlap the one below it by enough of a margin to allow the threaded rod to pass through. The staircase was then secured by way of the top tread to the deck, and to the ground by way of the lower tread. We used a tap and die set to tap holes in to the 3.5″ pipe of the base and placed set screws to tighten the base to the 2.5″ centre pole. We also made a custom bracket which was welded to the centre pole and secured to the roof trusses for added stability and added a couple of other brackets linking the treads to the roof along the length of it to secure it in place. Now it was ready to go.

Tah-dah! The staircase is behind the honey house so it feels like a secret that allows you to climb out of a forest in to the clouds. It’s quite magical really. It has been holding up well so far and it is very fun to climb. We’re really pleased with it over all and had a lot of a fun building it. Didn’t those ugly old oak door frames clean up nicely?

Next, came the earthen floor….

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