This project started when my wife saw a bunch of these incredibly fancy under-stairs kids' play houses online, and requested that I do something similar with the empty space under our stairs. I couldn't build one of those if I tried, and I wanted to build something a little less permanent that could eventually be removed when our daughter outgrows it, without any lasting damage to the walls. At first we thought we'd build a basic castle out of a few pieces of plywood, but like many other 3 year olds around the country, our daughter is COMPLETELY obsessed with Frozen (just Frozen 1...we're 6 years late to that, and still haven't seen Frozen 2, but close enough). So, I took some inspiration from the iconic Let It Go scene in the original Frozen, and the result is an under-the-stairs Elsa ice castle, made from two 4'x8' sheets of 3/4" plywood, complete with LED strip lighting. You can do this project with basic portable power tools (drill, circular saw, jigsaw) - no fancy woodworking skills required.

If you have a question, please ask in the comments! Also, if you like this project, please vote for it in the Woodworking and LED strip contests.

Supplies

Note: this material list is for exactly what I built. Obviously yours might vary slightly depending on the dimensions of your under-stair space and what you decide to build.

Materials

4' x 8' x 3/4" plywood (2)
3" L-brackets (10)
1-1/4" wood screws
Drywall anchors
Cabinet hinges (2)
Cabinet doorknob
Door pull
Assorted screws for hardware
Magnetic cabinet latch
LED strip light
Snowflake template

Tools

Drill and drill bits
Circular saw and guide (or table saw)
Jigsaw
Finish sander and sandpaper
Assorted spring and bar clamps
Staple gun
Shop vac and/or tack cloths
Primer
Light blue paint
White paint
Brushes
Paint roller
Glitter paint or glitter paint additive*

* I ordered this stuff but it did not work as well as I hoped

Step 1: Concept Design

I started by trying to get a general look and feel for what I wanted to build. Again, the primary inspiration was Elsa's ice castle from the first movie. I wanted a design that matched the sharp/angular feel of the castle, that was also practical and safe for small children. I also wanted to incorporate some of Elsa's more graceful curving/spiraling ice magic. And most importantly...I wanted this to be relatively easy to build - basically just a few pieces of painted plywood.

I searched online and found a lot of craft paper and cardboard ice castle designs that provided some good inspiration. After nixing the original regular-castle idea (see attached PDF), I started sketching various 2D ice castle designs using Powerpoint (no fancy CAD program needed). Powerpoint made it easy to play with different colors and different shapes/sizes for the windows/spires. We settled on the approximate design you see above - a castle with pointy windows, angled crenelations/battlements at the top (instead of square), and pointy spires; with ice-magic-spiral-thingies painted on the walls. The space under our stairs allowed for two walls, so one would have the door and the other would just have windows.

Step 2: Dimensions & Cut List

From the design ideas in step 1, I came up with dimensions and a cut list for the pieces. However, I didn't stick exactly to my original plan - once I cut out the main wall pieces, I sort of eyeballed how big I wanted the windows and spires to be, and tweaked it from there. So the drawings I've uploaded here are the final dimensions of what I actually built. IMPORTANT: you will need to measure the dimensions of the space under your own stairs and adjust accordingly! Also take into account your kids' height, whether you want them to be able to crawl through the windows, and how easily you want adults to be able to fit through the door.

I've uploaded separate images of each dimensional drawing above, but you can also download the whole thing as a PDF.

Under-Stairs Elsa Ice Castle Drawings.pdf
Download

Step 3: Start Cutting!

I don't have a table saw, so I did all the big straight cuts with a circular saw and a guide. For the inside cuts (like the windows), I drilled starter holes in the corners, then used a jigsaw.

Step 4: Practice Fit With Clamps

I wanted to make sure I actually liked how the spires looked before I screwed the whole thing together, so I attached all the pieces with clamps first. I also put three 3" angle brackets on the inside corner where each of the walls joined, and pre-drilled all the holes to attach the spires to the walls (this makes alignment easier later when doing the final assembly).

Step 5: Mount the Door

I attached the door and door hardware to make sure there weren't any issues there. Two hinges, a faceted acrylic cabinet knob (I figured it matched the "ice" look), a magnetic cabinet latch attached with a piece of scrap wood, and a door pull so you can pull the door closed from the inside (I forgot to take a picture of that one before painting).

Step 6: Sanding...so Much Sanding

I didn't take many pictures of this part, but...lots and lots of sanding. I took off all the clamps and unscrewed the brackets so I could lay each piece flat for sanding. Then I hand-sanded all the edges and corners (don't want any splinters or cuts when kids are playing!) and used a finish sander on the flat surfaces in preparation for painting.

Step 7: Reassemble With Screws

To get ready for painting, I reassembled the whole thing (except the door) with screws. Clamps come in handy to hold the spires in place if you're doing this part yourself, and remember that it will help if you pre-drilled the holes earlier. I didn't use any wood glue because I wanted to be able to take things apart easily, as I'd need to carry the whole thing from my garage to the basement eventually.

Step 8: Base Paint

I applied one layer of primer and two layers of light blue base paint, all with a brush. Watch out for runs at the top edges and window ledges.

Step 9: Decorative Spirals + Glitter Paint

I free-handed the "ice magic spirals," so I don't have a template for those. I practiced on the inside wall first, since that part won't generally be visible to guests. Once I was satisfied with those, I painted them on the outside. I also used the snowflake template I ordered to paint a snowflake on the door (which again, is inspired by the ice castle from the first movie). I realize that's cheating. If you're more artistic than I am, of course you can paint your own snowflake. Or if you have a laser cutter (I don't), you could cut your own template.

I tried using the glitter paint additive mentioned in the materials section for the ice spirals, the snowflake, and an additional coat of blue paint on the spires, but it didn't work as well as I'd hoped. The instructions say to use a roller for best results, so it didn't really work at all for the spirals (which I had to do with a brush). I used a roller for the snowflake and the spires, but even then, the light has to hit it at exactly the right angle to create a sparkle effect.

Step 10: Assemble Under the Stairs

I took the walls apart so they could be carried individually, but left the spires attached this time (the tallest one just BARELY fits through a door). You might want some help carrying the largest side wall, especially if you have to go down some stairs. Then I reassembled everything under the stairs, and once the fit was correct, anchored it to the wall using more L-brackets. It's pretty heavy and stable even without being anchored, but I predicted (correctly) that my daughter would immediately try climbing through the windows instead of using the door, so I didn't want to risk it falling over.

Speaking of the door, since I was installing this on carpet, I'd initially shaved an extra 1/8" off the bottom so it would open smoothly. That wasn't quite enough and it was still dragging on the carpet, so I had to trim off a little more, and sand/repaint the vertical edge of the door because it was getting stuck when it closed. This happened because the front wall piece twisted slightly when I secured everything. So in hindsight, you can probably get away with trimming a little extra off the door to begin with, if you want to save yourself a few trips back and forth to the workshop.

Step 11: Add LED Strip Light

I ran the LED strip light along the top of the inner walls. I didn't want any kids tripping or yanking the power cord, so stapled that to the baseboard/edge of the wall as pictured. I also knew my daughter would lose the remote, so I attached that to the wall with velcro sticky tabs.

Step 12: Bonus: Snowflake Chandelier

I don't have directions for making one of these, my wife just stole the leftover decoration after her office holiday party. But it makes a perfect chandelier, again inspired by the ice castle in the first movie! Search 3D paper snowflake and you can probably find instructions to make your own.

Step 13: All Done!

And that's it! The LED lighting looks way cooler if you turn off the rest of the lights in the room. An added bonus of the RGB LED strip is that you can change the color to match Elsa's mood (as fans of the first movie will know, it turns a reddish magenta color when Elsa is upset). Very handy for 3-4 year olds who like re-enacting scenes from the movie endlessly and making their parents be Anna...

If you've made it this far, thanks for reading! I hope this provided some inspiration for your own under-the-stairs project. If you have a question, please ask in the comments!