Index Card Castles {STEM Challenge}

Here’s a fun STEM challenge that works well with all ages, and the supplies are CHEAP! Grab a pack of index cards and a roll of tape, and set the kids to work building and designing castles. As it turns out, index cards are a great material for this!

I would recommend this project for kids ages 7-13, or 2nd grade through 8th grade. My 6 year old (nearly 7) built her own castle with only minimal help, and loved the process! Elementary students will do great with this. However, middle schoolers will also have fun with it and can create stronger and more elaborate castles.

Supplies Needed for this STEM Challenge:

• Index cards
• Clear tape
• Scissors

This engineering challenge could not be simpler. For the index cards, they can be either plain or ruled, but I would recommend avoiding heavyweight index cards. We had some heavyweight cards that we tried, but they don’t bend nicely into round towers. They just make creases when you try to bend them in a circle.

Doing this with a group? I would recommend one pack of 100 index cards per 4 castles. But that’s just an estimate based on what we used.

A great way to start building a castle is to make four towers for the corners. Then tape index cards to the towers to make walls.

Try making your towers square by folding the index cards into fourths instead of bending them into a circle!

If you want a circle shape for a tower, trace a cup. This is one of our go-to methods for getting a nice circle!

Then you can attach the circle to a tower like this. Cut two strips and fold them at a 90 degree angle. Tape the bottom of each strip inside the tower. Now you have the top of the strips to tape to your circle!

You can see the completed tower on the top of this castle.

Another fun idea is to add rounded roofs on some of the towers. We used colored index cards for this, which looked really good. Trim your index card to make a square. Then cut a slit that goes to the center.

My son made the taller towers by bending and taping an index card lengthwise. He also decided that he wanted a piece of paper for the base.

Here’s how to make the round roof piece. Start with a rectangle. We trimmed some off the end of the index card to make this shape. Then cut a slit to the center.

Slide the card past the slit to make a cone shape. Use tape to secure it.

Then trim around the bottom in a circle shape.

This was our biggest castle, built by my 14 year old. Attach more than one index card together to make larger towers. It’s amazing what you can build with just index cards and tape!

Tips for Expanding the Index Card Castles Project:

• Try cutting windows before assembling the castle! They can’t easily be cut afterwards.
• Decorate the castle with markers or colored pencils.
• Make index card knights, horses, kings, and queens for the castle! Make them stand by attaching them to a strip of index card bent into a ring and taped.

Need more STEM challenge ideas? Here are 30+ Engineering Challenges with Simple or Recycled Materials!