STEAM Corner: Build a Roman Arch


April 27, 2020

By Jess Alexander

Categories: Kids & Families, STEAM

Welcome back to the STEAM corner, a blog series featuring Science, Technology, Engineering, Art, and Math projects to do at home. Today’s family build requires cutting, pasting, and cooperation, which makes it ideal for keeping hands and brains occupied while the Library is closed.

Stay home. Stay safe. Stay STEAM-y.

Want to show off your project? Share your pictures and videos on social media and tag the Library!



Roman Arch

Assemble a set of trapezoidal blocks into a free-standing Roman arch.

In ancient Rome, arches supported the weight of giant structures, including bridges, aqueducts, and the Colosseum. Wedge-shaped blocks press together to maintain the semicircular shape.



  • 7 block templates (print this PDF onto cardstock or hand draw onto cardboard junk mail)
  • Scissors
  • Glue or tape
  • Weights (rocks, pennies, etc.)



Step 1: Cut out 7 cardboard block templates.

Roman Arch - step 1


Step 2: Fold templates along dotted lines.

Roman Arch - step 2


Step 3: Glue flaps to form blocks shaped like trapezoidal prisms.

Roman Arch - step 3


Step 4: Work with a buddy to assemble the blocks into an arch. No glue needed! Weigh down the end blocks to prevent sliding. The middle block is called the keystone. Without the keystone, your arch will collapse.

roman arch


Math Connection

roman arch math

Our arch is built out of isosceles rectangular prisms. Imagine that the legs are extended to form triangles that meet in the middle. The sum of those vertex angles must equal 180°.

Divide 180° by the number of pieces in the arch to find the measure of the vertex angles.

5 pieces: 180° ÷ 5 = 36°

7 pieces: 180° ÷ 7 ≈ 26°

9 pieces: 180° ÷ 9 = 20°


Soundtrack Note

The official accompaniment to this project is “Lean on Me” by Bill Withers. The Club Nouveau rendition is also acceptable.

Jess Alexander is a Youth Services Librarian at Morton Grove Public Library.