Introduction: Roman Arch

An architect is the person who plans the construction of a building. The architect designs the shape of the building, chooses the materials it will be built with, and it is architect’s responsibility to prove that the building will be durable, safe, and won’t fall down.

Architects have a lot of responsibility, but they also make a lot of exciting and creative decisions. In this lesson we will learn about some basic principles of architecture, and experiment with architecture in Tinkercad.


  1. Continue to the next step.

Step 1: Introduction

Before there were lumber yards and steel beams the walls of many buildings were made by stacking stone bricks.

As you can imagine this made it difficult to make doors and windows. The arch allowed architects to design walls with doors and windows, and it is a structure made entirely of stacked parts.

In this lesson we will learn why stacked arches don’t collapse, and we will build our own stackable parts that can be assembled to make an arch.


  1. Trapezoidal brick - An arch is a sequence of stacked stones that creates a curve. Each side of the arch leans inward because some of the stones are trapezoidal.
  2. Keystone - The keystone is found at the very top and center of the arch, and it must be trapezoidal. Its the last stone stacked when assembling an arch.
  3. Impost - The bottom stone in the arch. The impost rests on the ground or the foundation.
  4. Abutment - The structure which accepts the outward forces produced by the load on the arch.
  5. Continue to the next step.

Step 2: Make Your Keystone and Trapezoid Shape

We’re going to build the parts for our arch upside down, so we will make the keystone first.

When the keystone is in place it will be at the top of the arch wedged between bricks on either side. This trapezoid shape will also be reused throughout the arch


  1. Drag out a triangular roof and scale it along the Z axis to 31.5mm.
  2. Drag out a box and move it 20mm upward along the Z axis.
  3. Center the box to the roof along the X and Y axis, turn the box into a negative space, or hole, and group it with the roof.
  4. Continue to the next step.

Step 3: Change Workplane

Changing the Workplane will allow us to position objects in relationship to each other in ways we could not otherwise.


  1. Drag the Workplane helper to one of the sloped faces on the trapezoid prism.
  2. Continue to the next step.

Step 4: Add a Box

Now that we’ve changed our Workplane we can add a brick to our arch. Not every brick in the arch needs to be trapezoidal. The next brick in our arch will be a box.


  1. Find the word “Workplane” on your screen and use the 3D modeler’s salute to make sure you know which axis is which. The word “workplane” will be parallel with the X axis.
  2. Drag a box onto the work plane and center it to the keystone along the X axis.
  3. Align the box to the lowest limit along the Y axis.
  4. Continue to the next step.

Step 5: Add Another Trapezoid

Now we want to place another trapezoid in our sequence of bricks.

To put it in place we will need to change the workplane and use the mirror tool.


  1. Set the Workplane to the bottom of your box.
  2. Align your items to major gridlines.
  3. Select the trapezoidal keystone and duplicate it.
  4. Move your new trapezoid to the opposite side of the box.
  5. Use the mirror tool to flip the trapezoid around the x axis and align it with the box.
  6. Continue to the next step.

Step 6: Add a Group of Bricks

Now we're going to repeat the last step, but with a group of bricks instead of just one.


  1. Set the workplane to the bottom of your new trapezoid.
  2. Select and group your original trapezoid and box.
  3. Align all your items to major gridlines.
  4. Create a duplicate of the group you made.
  5. Move your new group to the opposite side of the trapezoid.
  6. Using the mirror tool, flip your group around the X axis.
  7. Manually align your new group to the trapezoid.
  8. Continue to the next step.

Step 7: Prepare to Complete the Arch

We’re almost done with one side of our arch, now we will prepare it to be duplicated and used as the other side.


  1. Group all of the objects.
  2. Reset the Workplane by dragging the Workplane helper to empty space.
  3. Align your group to a major gridline.
  4. Continue to the next step.

Step 8: Mirror the Arch

We’ve built one side of our arch, to build the other side we will create a duplicate of the complete side and mirror it.


  1. Ungroup your parts and then regroup all the parts except for your keystone.
  2. Duplicate your group.
  3. Mirror the group around the X axis.
  4. Align the group with the opposite side of the keystone.
  5. Group everything.
  6. Continue to the next step.

Step 9: Make the Imposts

Imposts are the bottom stones in the arch, they rest of the ground and all the bricks in the arch rest on the imposts.


  1. Rotate the arch 180° around the Y axis.
  2. Move the arch 20mm upward along the Z axis.
  3. Drag out two boxes, center and align one beneath each side of your arch.
  4. Scale each box along the Y axis so that it is the same width as the brick above it.
  5. Group these boxes with your arch.
  6. Continue to the next step.

Step 10: Make an Abutment

Imagine trying to stand with your legs far apart while wearing socks on a slippery floor. The weight of your body would push your feet outward.

If we try to stack all of our parts the imposts will slide outwards. An abutment will prevent the imposts from sliding outward. When buildings were made of stone the walls on either side of the arch would often serve as the abutment.

We're going to make a very simple structure to serve as our abutment.


  1. Drag the workplane helper onto the top of your keystone. Drag out a box.
  2. Resize the box to be 20mm along the Y axis, 6mm along the Z Axis, and 130mm along the X axis.
  3. Center this box to the arch along the X and Y axes. Copy the box.
  4. Drag the Workplane helper to the outside surface on one of the imposts and paste your box.
  5. Align the box to the bottom of the impost. Shorten the length of the box so that it is the same height as the top of your first box.
  6. Copy your box.
  7. Set your workplane to the opposite impost, paste your box, and align it.
  8. Group these three boxes.
  9. Continue to the next step.

Step 11: Prepare for 3D Printing

Now we need to prepare our parts to be printed.

We will make sure they’re all lying down flat on the workplane, and they’re evenly spaced 1mm apart.

Instead of taking apart our arch to print the parts we will simply make copies of all the parts and delete the original arch.


  1. Rotate your abutment 180° around the Y axis and set it aside.
  2. Ungroup your arch.
  3. Duplicate your keystone and one box. Set them aside with the abutment.
  4. Delete your original arch.
  5. Rotate your keystone 180° around the Z axis.
  6. Align your box to the abutment to its lowest limit along the X axis and space it 1mm away along the Y axis.
  7. Align your keystone next to your box with 1mm between them.
  8. Select your box and keystone. Duplicate them and translate 21mm forward, leaving a 1mm gap. Use smart duplicate to create 4 more pairs and delete one of the keystones so that you have 5 keystones and 6 regular boxes.
  9. Align the abutment with the row of bricks.
  10. Continue to the next step.

Step 12: Printing

This print should not be challenging for your printer, but it has a large volume that could take a long time.

Print these parts at high-speed with sparse infill.

  1. From the Export menu, click the button labeled 'STL' in the 'For 3D Printing' section.
  2. When your browser has completed downloading, load the file in to your 3D printer software.
  3. This object doesn't require any special settings.
  4. Print!