Shaker Two Step Stool, Part 1: Design Considerations

A neighbor is having their kitchen renovated, so I asked if I could get the solid wood from the cabinets that were getting ripped out.

A whole bunch of red oak

I got the wood from all the face frames and the drawer fronts.  It takes a bit of work to make this wood usable, but hay, it's free wood.

I've been wanting to build a Shaker two- or three-step stool for a while.  I got some ideas on a design from an image search and came up with this.

The overall design

There are so many questions to answer when designing something.  I start from function.  I wanted a step stool about 18" tall to help get to some higher shelves in the garage.  So the first step is at 9" and the overall height is 18".  For the overall width, I chose 15".  This is the same width as some simple four-legged (staked?) stools I've been making and is plenty wide for me to place two feet side-by-side comfortably.

I've read that Shaker step stools were meant to be used directly against a wall.  Such stools were vertical at the back.

Typical Shaker step stool with straight back edges (3-step version)

Since I wanted to be able to use the stool away from walls without it tipping over backwards, I added a slant to the rear edge of the sides.  I matched that angle on the front edges.

Slanted back edge and matching slant on front edge

If the front edge of the side extended up to 18", the total span of the top step would be 12".  At the bottom, the distance front to back is 16".  So I have a 2" deviation in 18 vertical inches at both front and back (if that makes sense).  This slant turns out to be an angle of 6.3°.  The angle wasn't really important - it just needed to look like I wouldn't risk tipping it backwards when I'm on the top step.

Side dimensions

There's an interesting thing about this.  The front edge of the top portion of the side is dead center of the design.  You can see from the picture that the base is divided up evenly.  I intended to do this, but the undesired effect is that the first step is 7" deep whereas the top step is 6" deep.  I think I'd like them be the same.  I might feel a little safer with deeper steps, but I didn't want this thing to have too large a footprint.  I'll use a prototype to make sure it feels OK.

I wanted to dovetail the steps and sides together and needed to decide about dovetail layout.  But I also wanted a rail under the front of each step, so I couldn't have a half-pin at the front and back ends of the side boards.

Upper step dovetail and cross-rail layout

At the front and back of the step are "half-tails".  I needed to have a tail at front to rest on the cross-rail.  And I added one at the back for symmetry.  I played with the dimensions a bit before deciding on a four-tail design, with the two middle tails being a bit wider than the front and back tails.

I used a similar layout on the lower step, just each tail was 1/4" larger since the lower step was 1" deeper than the upper step.

The two front cross-rails will have their lower edges dovetailed into the sides.  The shoulder of the dovetail will add a bit more resistance to racking than if the rails were not dovetailed.  There's a bit of added complexity for the lower front cross-rail - it fits into an angled edge, so it's upper edge will need to be beveled to mate well with the underside of the step.

Upper cross-rail detail

There will be a cross-rail in the back for even greater stability.  It will be dovetailed into the sides as well.

Back cross-rail detail

I was not too particular about the vertical location of the back rail.  I ended up placing its top edge about even with the top of the first step.

One of the last things I considered was the arch cutout on the sides.  I didn't want the feet to be too wide or too small.  But the main thing I was concerned about was the amount of wood keeping the right half (lower step portion) attached to the left half (upper step portion) of the stool.  I think that's the weak point in this stool design.  If the wood is going to fail, it's going to fail just above the center of the arch.

Original arch detail

At first, I laid out the arch as a full semicircle.  That made the arch 5" high, leaving only 3 1/4" of wood above the arch keeping front and rear portions of the stool together.  So I dropped the arch down to 3 1/2" high to add 1 1/2" more wood above the arch to help keep the stool together.

Arch detail

As an added benefit, I think I like the lower arch shape better.

So much for the design.  Next time I'll go over the prototype build.