Brief Description:

Students will be guided through this activity, building a triangle, a square, and a braced square using LEGO pieces. Students will then attempt to build a sturdy box on their own with LEGO pieces from their kit.

Grades: K-3

Time: 1 hour

Concepts: sturdy structures, civil engineering, strong shapes, bracing, axle, bushing, pegs

Lesson Objectives:

  • Familiarize students with specific LEGO building strategies and new pieces.
  • How to use pegs (friction and connection).
  • Building a triangle and a square.
  • Bracing with beams.
  • Teach the names of LEGO building pieces.
  • Reinforce knowledge of shapes.


  • Lego Simple Machines kits


  1. Review sturdy building and names of pieces (it may help to have an overhead or poster of pieces and their names):
    1. Overlapping beams and bricks are stronger than non-overlapping ones
    2. Three stacked plates are the same height as one beam.
  2. Show students how to build in ways other than stacking pieces (pegs, axles and bushings, etc.).
  3. Have students make a triangle.
    1. Show students on your example how you can use both pegs and axles with bushings to connect beams.
    2. Push on your triangle to show how strong and sturdy it is.
  4. Show students a pre-built square
    1. Show on your demo model that the square is not sturdy and talk about why.
    2. Have students brainstorm ways to make a square sturdy.
  5. Have students build a square and add a diagonal brace to their square to make it sturdy.
    1. Show students that by adding the brace you have created two triangles and remind students that triangles are very sturdy shapes.
  6. Have students use this new knowledge to build a sturdy box.
    1. Use the Engineering Design Process in the process of building the box.
      1. Plan and Create: Build the box using the pieces introduced in this lesson
      2. Test: apply 2 tests
        1. Flick Test – the box won’t collapse when pushed
        2. Drop Test – box doesn’t break when dropped from ankle height.
      3. Redesign: Rebuild the box until it passes the tests. Consider ways to make the box stronger.
      4. Share: Come together as a class to share designs.
        1. Talk about difficulties that different groups had in building their box and how they overcame these difficulties.
        2. Identify different shapes in the boxes and the pieces that the groups used.
        3. Talk about ways that different groups made their boxes stronger.
        4. Look around the classroom for examples of sturdy shapes and sturdy building.

Extensions and Modifications:


  • Extended introduction, emphasis on teamwork:


      • Introduce engineering by reading What Do Engineers Do? (available at the CEEO) and discuss how engineers often work with other people to accomplish goals.
      • In this activity, students will be introduced to partner building. Students will work with a partner to build the above as well as a design of their choice, but must cooperate, discuss, and compromise as part of the challenge.


  • Other challenges that day:


      • Build the widest/longest structure.
      • Build the strongest structure using only 10 pieces.


  • Three Little Pigs: Build a Sturdy House:


      • The final Sturdy Box activity can be expanded into a three little pigs activity. In this activity, students will use the knowledge they learned in this lesson to build a sturdy house for the three little pigs.
      • Students can be challenged to build the sturdiest house out of 1) paper 2) straws and popsicle sticks or 3) lego bricks.
      • After building, they can test their structures with a drop test and a “big bad wolf” test (place the structure in front of a fan) to see which ones are the sturdiest. What worked? What did not work?


  • Build a Colonial Home


      • The final Sturdy Box activity can be expanded into a history/IEL lesson in which students build sturdy structures for the colonists.
      • Read Living in Colonial Times and discuss difficulties experienced by colonists due to limited resources.
      • Build sturdy homes using cardboard, paper, popsicle sticks, straws, pipe cleaners, tape, q-tips, and toothpicks


  • Bunk House for Paul Bunyan


    • The final Sturdy Box activity can be expanded into an IEL lesson in which students build sturdy structures for the Paul Bunyan.
    • Read Paul Bunyan. Identify problems with Bunk Houses and brainstorm solutions to make them better.


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