Easy Method for Curved Stairs

Normal stair cases are tricky, curved stair cases are a different level of tricky.

In this video I’ll show you a unique and easy method we used to build this set of curved stairs to go up to the floating tree deck that I built. Be sure to check out that build if you haven’t already seen it.

First off, big thank you to my friend Tim Uhler (Awesome Framers) who told me about this method of stair building.

Unlike a normal set of stairs where you place the stringers first then set the risers and treads, this method calls for the stairs to be build individually first, then placed on stilts, then connected to one another. That might not make sense right now, but it will soon.

I first started working on cutting all the risers while Jacob started attaching the header to the deck. BTW: if you missed the deck build, check it out HERE

Since we’re building this staircase outside and on uneven ground, Jacob built this temporary platform to give us a level working surface for constructing. Then he also already poured the concrete footers where the bottom of the stairs will end. 

I was ready to start putting together stairs after getting the risers knocked out. 

For assembling, the order is a 2×4 is placed on the 2×12 riser, this will later support the next steps’s sub tread.

Then the sub tread is connected to this face of the 2×12. Construction adhesive is used before attaching each piece. 

After repeating to make up all 14 stairs, we could start adding stilts to the underside. These will be just temporary members so no construction adhesive was used, just driving in two screws per board. Then we were able to start standing it up, and this is where you’ll see how it comes together.

The sub tread of the step being stood up, connects into the 2×4 of the step ahead of it…of in this first steps case, the header on the deck. Then you can repeat with each step following until they are all up in the air and connected. 

For attaching, we would lay down a bead of construction adhesive on the 2×4 then drive in a few screws once the sub tread was in place. Since Jacob had a model of this entire case before we ever got started, he was able to create a layout on the platform showing where each 2×4 post should be landing.

This allowed us to quickly set them up, move them into position, screw down the top, then also throw in a screw at the base to keep it from moving. It was amazing just how quickly all of this came together, I mean in less than an hour we had a staircase we could use to get to the top of the deck. 

Now before you start leaving me comments about how nothing about this is correct, we aren’t done. 

With the steps in place, next we started building the stringers, or what will take the place of the stringers. Instead of 2x12s that you typically see stringers made out of, this unique staircase is using half inch pressure treated plywood laminated together to build up to the thickness needed.

Instead of using a full sheet o plywood we ripped down some strips to make holding it up in place easier. We first set some clamps and made sure that the top was overhanging all of the steps. We applied construction adhesive to all of the 2x12s, 2x4s, and 1/2” sub treads…trying not to get it on the 2×4 silt as we will want to remove that later…..then used screws to attach this first layer. 

Before putting on the bottom piece of the first layer we used she DAP clear caulking to seal the end plywood that will be in contact with the ground. This way it won’t be able to soak up moisture. We attached it the same as the first. 

Once that was fully attached next we trimmed it up to the stairs. This was done with a combination of a jigasaw and router.

A jigsaw to first remove the bulk waste which makes the router bit in the next step not have to work so hard. Then a flush trim bit in a router to get it all nice and flush. It creates a mess, but it’s a quick way to get it done. 

After repeating that same process on the inside of the stairs, we next started adding the treads on top of the sub treads. This is a piece of 3/4” material, again all of this material is pressure treated.

This step is very quick as we just needed to lay down some construction adhesive to the sub tread then set the top tread in place, making sure it was lined up flush, then screw it down.

And here, Jacob has a good trick. To make driving in screws easier, you can use a hammer to tap them into place first. This gets rid of the wobbling around phase when driving in screws.

Oh yes, we also made sure to blow off the step before laying down construction adhesive so the tread would lay nice and flat. 

By the way, those circles in the center of the steps are weep holes. They will give any moisture a way to escape instead of getting stuck. It’s really cool to feel the entire structure get stiffer and stiffer the further we build. 

After reinforcing the steps, next was to add more plywood to the sides. We started off on the inside of the stairs as the concave surface would be the most difficult.

Before moving to the outside to laminate with plywood, we stopped to tape the stairs. And honestly, it would have been better to tape before laminating the inside, because then the tape could just run off both sides. The tape is a time consuming step, but it will drastically extend the lift of the material, so it is worth it. It creates a barrier between the wood and moisture.

Next we moved to the outside and this side is much easier to film and show off the process.

We started by laying down a qood amount of construction adhesive to layer one, then adding on layer two. The most important thing to pay attention to in this step is to get a good connection with no gaps so that these individual layers become one solid piece, giving the support needed.

It’s kind of tricky because both ends require two different cuts. So we would cut one end and start attaching it. Then we would hold up the next board and scribe it to make finding the angle much easier.

Utilizing clamps at the start to make sure it sucked down flush to the curve. With this being a convex curve, it was much easier to bend and shape. To hold it down permanently, we would locate the 2×12 riser of each step and throw in a few screws. 

With the staircase being the length it is, this process took two pieces of plywood to cover the entire length. No problem, we just made sure the seam butted up nice and tight when attaching the second piece.

After layer two, we repeated with layer three, and then eventually, layer four. Ha, Jacob says this is the biggest paper mache project he’s ever worked on. 

Don’t pay any attention to the bottom, all of that will be shaped and cut off later on. Right now, only the top surface matters as it’s the one staying forever. 

Next up was to take off the 2×4 stilts. Since we only put these in with two screws from the front of the stairs, we simply had to unscrew them from the front of each one.

Even though we were mindful on where we placed adhesive, some still needed a little bump of persuasion to let loose. Haha. My goodness, it’s incredible how solid they felt. Very little defection was felt even when full blown jumping up and down on them. 

Ok, lets pretty it up some. This was done by shaping the plywood and can of course be done in any manner of shapes and ways.

I did subtle curves to make it a little unique then cut along my line with a jigsaw. After the cut, this can be sanded to clean it up a bit then called finish. Well for that portion anyways. 

For the steps, they still needed to be decked. We’re once again using the Trex composite decking in order to match the deck’s decking.

Wow, what a transformation. Also, just way more convenient than moving a ladder into place every time we want to sit and enjoy the deck. 

Of course it till needs a coat of paint, no I don’t plan on leaving the pressure treated plywood as is…but the material still needs to dry out a few more weeks before it will accept a coat of paint, so stay tuned on the final look of it and the underside of the deck. 

In the future we will be adding unique railing to not only the staircase but also the deck itself.

I really hope you enjoyed watching this project come together. It has certainly been one of my all time favorite builds and a heck of a lot of work. I’ll see you on my next project. 

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