Introduction: Cardboard Cat Fort With LED Remote Control Lighting and Real Drawbridge

About: I'm a tiny woman in a big city and I like to make stuff. Crafting is a way of life, my religion is Lego and I cross stitch like a BAMF.

My two precious pet cats are princesses... in the second listed dictionary definition sense:



a spoiled or arrogant young woman.

It's probably my fault – they only have to look at me with those little whiskered faces and I'm helpless. Given their regal demeanour, it's only fitting for the princesses to have a castle or fort to play in. So, being the doting cat slave I am, I set about building a feline fort, complete with moving drawbridges and remote control LED lighting.

Deciding on the building material was easy – I think we've all got a bit more cardboard handy now social distancing is in full effect across the planet, and many of us are taking our shopping compulsions online.

If you want to make your own, you will need:


For the fort:

  • Cardboard
  • LOTS of tape
  • Scissors
  • String
  • Pencil
  • Ruler/tape measure

For the magic lighting:

  • A few white LEDs (I'm using 5)
  • Plenty of narrow gauge electrical wire (I'm using thin stranded wire)
  • Current limiting resistor (Value will vary depending on how many LEDs you use and what battery)
  • Batteries for LEDs (I'm using 2x AA batteries)
  • 2 BBC Micro:bit micro controllers (with battery packs and USB cable to program them) - A transistor (I'm using 2n7000) - Crocodile clips/jumper cables - Optional: breadboard (makes connecting everything easier. But you can use another method if you like – conductive paint, solder, twisting the wires together...)

Step 1: STEP 1 – Pick the Layout and Plan

Start by gathering all the boxes and cardboard you have, so you can block out the rough arrangement for your fort.

You want to think about which boxes are going to connect to which, whether you want the layout to be symmetrical, and how you can include variety – don't have every box connect to every other on the same level; make some of the holes higher or lower, some narrower or wider, some different shapes so there's more to explore.

Another thing to consider is how cats love vertical space. No castle is truly complete without a turret, so that seemed like an obvious thing to include, but cardboard is not the most structural building material so you have to strike a balance between height and stability. In our design, the tallest part of the fort would be securely taped to the base on multiple sides and have support from a wall on one side, so we knew our feline superiors would be safe.

Also, think about how you can include other cat toys or paraphernalia you have – in our arrangement I incorporated a flat area just big enough for our cardboard scratching pad. It looks a bit like a balcony garden, a "clawn" garden, if you will. One of the upgrades we already have planned is to add a dangly feather toy, disguised as a flag pole.

Once you've laid out all the boxes in the rough arrangement they'll fit together, take a picture. You can draw over this picture to visualise the final result and it will also be a handy reminder when it comes time to assemble, since you'll have to deconstruct your arrangement to cut windows and doors.

Now is also a good time to plan your windows. Cats' night vision might be much better than ours, but you probably still want a couple of windows for your sake, not theirs. Why build a cat fort if you can't watch your fur babies explore it?

It's wise to plan other embellishments and features at this stage, to make sure you have enough cardboard. We decided on draw bridges, which didn't require extra cardboard, but also some crenellations (yes, I learned that word for this tutorial, so we're all learning together), which we needed to keep some cardboard spare for, as well as steps up to the turret. That meant we also had to plan what cardboard would be best used where – we wanted to retain some of the sturdier stuff for building

Step 2: STEP 2 – Draw Bridges and Windows

If any of your boxes are open, don't seal them up yet – this will mean you have easier access when you're fitting them together and cutting out details.

First, we marked out our draw bridges. Measure up and draw a line vertically down the centre of one face of your box. Pop a dot along this line at the point that will be the pinnacle of your draw bridge. Next, draw a half circle using this point as a guide before drawing some vertical lines from the edges down to the edge of the box. Once you've cut it out, if you punch a couple of holes in the drawbridge along with two corresponding holes in the roof of the box, you can loop and tie some string through them so you'll be able to actually raise and lower your drawbridge.

When it comes to windows, we went for variety and aesthetics over historical accuracy. Those posthole type windows won't keep any arrows out, but the only projectiles likely to be aimed at Fort Cat are Dreamies, thrown by me, so I daresay that doesn't matter so much. We drew around a small bowl to make the circular windows and measured roughly for the others.

Take care when cutting if your boxes aren't sealed – your feline superiors might want to inspect the work. They can be stealthy and are famously reckless with their safety, given that they have nine whole lives to work with, so keep them out to avoid accidents. Plus, it's better for them to have the surprise of seeing the finished product, even if they don't see it that way.

Step 3: STEP 3 – Main Assembly

Now you've cut your doors and windows and figured out what arrangement your boxes are going to go in, it's time to create the main architecture of the fort.

There are lots of different ways to join different boxes, but we found that common sense and a lot of tape were more or less all we needed.

To make a pathway between two boxes of same height, on the same level, we cut a panel out of one of the boxes and made a "H" shaped incision in the other. Slide the boxes together, then open the two flaps created by the "H" cut into the other box and tape them down inside. This kind of join is particularly useful for when you've only got access from one box, if the other has been sealed or joined to another box already.

For the vertical join between the level under the "clawn" garden and the inside of the turret, we drew around the turret box placed on top of the box below. Then, we measured up and cut corresponding squares the same in each box, put them together and taped around the sharp edges on all sides.

Seal up any remaining open boxes.

Step 4: STEP 4 – Adding Embellishments

Time to beautify the box fort.

The main embellishments we added to Fort Cat were the strings for the draw bridges and the crenellations (the square edging bit) around the turret and along the mini balcony. The string lets us actually articulate the drawbridges. Funnily enough, the cats have learned to lower the drawbridges by themselves, but not raise them. The crenellations were made from some thin cardboard packaging cut to fit and taped around the turret.

As you can see from the video above, Princess Magna was a big fan. She ate almost all the edging before I could even get the final photos of the fort.

I thought about adding embellishments to the windows, like sills or arches, but since the cats had already eaten a significant portion of the other embellishments it seemed like a futile exercise.

You could opt to paint yours – just make sure whatever paint you use is pet safe, especially if yours have as powerful a hunger for cardboard as ours do. We decided against paint, since we liked the rustic appeal of the brown and red cardboard offset by the vibrant danger tape.

Step 5: STEP 5 – Building the Stairs

Dividing the distance by the height of our cats (in case you were wondering, no, it was not easy to measure our cats), we figured we'd need about two additional steps to provide a graceful route to the top of the turret. Of course, the cats could definitely just fling themselves up there, like they fling themselves at the coat rack, but that's not very lady like. We wanted to encourage some decorum in Fort Cat.

We ended up making two different kinds of steps: one box step and one step on stilts.

The step on stilts had two stable pillars to support it, and double thickness cardboard for the actual platform. To make the pillars, I took two strips of cardboard that were about four inches longer than the height I wanted the step to be. The strips don't have to be super wide, but don't make them too narrow either, mine were about 20ish cm, maybe 30. I scored them vertically so the strips had four equally spaced vertical lines, then I rolled them up, overlapping the two end sections so that I ended up with two triangular columns. Next, I cut two inches or so down each score line at both ends to create tabs. After bending these tabs out, away from the inside of the pillar, I used them to attach the pillars to the platform part of the step and to the box that the step was on top of.

(It's a bit difficult to explain in words, so hopefully the pictures show basically what you're aiming for.)

To make the other step, I just took a medium sized box, cut it open on one side and laid it out flat before refolding in a slightly different way to make a smaller box. I then taped this box securely in place.

Step 6: STEP 6 – Adding the Lighting

Well, LED lights aren't quite chandeliers, but we all know how long a chandelier would last with cats around. Irresistible dangly playthings.

Our babies are little void monsters, one of them as black as the inside of a cardboard box, so even if we couldn't have chandeliers I really wanted to create a little mood lighting for fort cat – especially since the cardboard castle is in our bedroom. I loved the idea of being able to watch them exploring their dominion with the room lights off, because obviously cats are most active just about as soon as you turn off the lights and look like you don't want to be disturbed. So, I added a white LED light to the roof of each room in the fort and hooked them up to a battery... but the trouble then was that I'd have to get up to switch the lights on and off, either disturbing the cats or my sleep.

My solution was to create a makeshift remote control using two microbits, which are cheap and easy to program micro controllers.

I'll explain he gist of it here, but if you want a more detailed explanation of how to set up your remote control LED lights, I made a video about this that you can watch instead:

First, I connected my 5 LEDs in parallel, with long stretches of wire between them and a current limiting resistor at the end. Instead of soldering the wires, I just twisted my stranded wire around the legs of the LEDs and taped in place – this saved time and was a perfectly viable short-term solution. After poking each LED through a small hole in the ceiling of the cardboard boxes, I covered the wires between them with a good, chew-proof layer of tape.

Then, I got out a transistor (2n7000) and plonked it into my mini breadboard. Using a combination of crocodile clip and jumper wires, I connected the negative end of my string of LEDs to the transistor's right leg (transistor's flat side facing towards you), and connected the transistor's left leg to the negative terminal of the battery I was using to power the LEDs. Next I added a microbit, connecting pin 0 to the transistor's middle leg and ground to the transistor's left leg. Once you've put some code on your microbit, powered it up and attached the positive end of the LED string to the positive terminal of its battery pack, the microbit will be able to turn the lights on and off through the transistor, which is operating like an electronic switch. I enclosed all the electronics in a Tupperware container.

The second microbit will send a signal to the first via radio, which will be the trigger for turning the lights on and off.

Here's a link to the code for the transmitter and receiver microbits:


Step 7: STEP 7 - Enjoy

Fort Cat is finished! Take lots of pictures of your hairy princesses exploring their new abode, and keep lots of cardboard spare for renovations.

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