Building Strong Structures

At the beginning of our Engineering Unit, we studied Towers – where the goal is to build a structure as tall as possible. In this session, we work to build a structure that’s as strong as possible. You can read the full Structures Lesson Plan here. In this post, I’ll just share some samples of materials we use in our buildings.

Toothpick Structures

For this method, you can use toothpicks with marshmallows or gum drops, grapes or cheese cubes. (We use “spicy gum drops” because the kids don’t eat more than one of those!) Kids can build as simple or complex as they like.

One way I scaffold this activity is shown in the diagram below. If they only have vertical and horizontal bars, the structure tends to be wibbly-wobbly. If you put in a diagonal truss, it makes it much more stable. But the toothpicks aren’t long enough to stretch from one corner to another, so you need to use 1.5 toothpicks with a gum drop joint in the middle, or extra long toothpicks. After they’ve learned this ideas, you can extend it to ideas like building a series of triangles – like a truss bridge or a geodesic dome.

Interlocking Cardboard

By cutting slits in cardboard, you can create interlocking pieces that make much sturdier buildings than if you just stacked the cardboard. I recommend the first method shown below – the round TP tubes are hard for kids to assemble. (You can also help your child notice how many building toys lock together in some way: Legos, Lincoln Logs….)

I’m also intrigued by this project from Fairy Dust – punching holes in TP tubes and using straws (or pencils or dowels or tinker toys) to hold them together.


If you’ve built towers with cups, boxes, tubes, or blocks (as shown in our Towers post), you could demonstrate to the child how much sturdier their tower can be if they use fasteners such as tape, glue, binder clips, or string to attach items to each other. (You’ll want to remind them that they’re not allowed to glue things together without asking your permission first.)

Different shapes

Explore the idea that different shapes are sturdier. Try building some square columns and some round columns – which can hold more weight? Try adding an accordion folded layer into a building. Can it now hold more weight?

Strength Testing

You can test strength in a couple different ways. One is to return to the method from the Towers week of trying different methods to knock the building down. And every time you knock it down, you try re-building it stronger. The other is the “how much weight can it hold” challenge. Try the index card bridge method or the binder clip and popsicle stick method.

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