How Much Weight Can Your Sandcastle Hold?
AbstractDo you think a sandcastle can support a brick? How can you change a sandcastle to make it support more weight? Find out in this fun science project!
Find out if adding layers of mesh window screen to sandcastles can help them support more weight.
Building sandcastles is a fun summer tradition for kids at beaches and in sandboxes everywhere. Some people build basic sandcastles from a single mold, and some people build huge, elaborate sandcastles and enter them in competitions!
Figure 1. Left: A basic sandcastle built from a single mold. Right: A huge, fancy sandcastle.
Sandcastles are built from many individual grains, or small particles, of sand. Dry sand is very loose and hard to build with because the grains slide over each other easily. Sand that is slightly damp and packed together works better for building sandcastles. Even with tightly packed damp sand, though, sandcastles usually cannot support very much weight. You have probably noticed this if you have ever smashed a sandcastle by stepping on it.
In this project, you will build sandcastles and stack bricks on top of them to see how much weight they can hold. You will build some regular sandcastles and some sandcastles with pieces of window screen between layers of sand. The window screen is a mesh—a grid with tiny holes in it. These holes can help prevent the grains of sand from sliding around. Do you think your sandcastle with added window screen will hold more weight? Try it and find out!
Terms and Concepts
- Do you think a regular sandcastle can support a brick?
- Do you think adding layers of window screen to your sandcastle will make it stronger?
- The Guardian (July 31, 2019). How to build the perfect sandcastle. Retrieved May 31, 2022.
For help creating graphs, try this website:
- National Center for Education Statistics, (n.d.). Create a Graph. Retrieved June 25, 2020.
Materials and Equipment
- Access to damp sand, either at the beach or in a sandbox
- Window screen (available at a hardware store)
- Bricks or other heavy objects (such as cans of food) to use as weights
- Lab notebook
- Prepare a table like Table 1 in your lab notebook.
|Number of bricks held|
|Type of sandcastle||Trial 1||Trial 2||Trial 3||Average|
|Without window screen|
|With window screen|
- Pack damp sand firmly into your bucket until the bucket is full.
- Flip the bucket upside down. Gently tap and shake the bucket, then slide it up off the sand to make your sandcastle (Figure 2).
Figure 2. A basic sandcastle made with a bucket.
- Gently place a brick flat on top of the sandcastle. Do not drop the brick onto the sandcastle.
- If your sandcastle supports the brick, gently add another brick on top of the first one. Keep adding bricks until the sandcastle collapses.
- Record the number of bricks that the sandcastle supported in your lab notebook. This is the number of bricks the sandcastle supported before it collapsed. If your sandcastle collapsed with the first brick, you would write "0" in your notebook.
- Repeat steps 2–6 two more times, for a total of three trials with the "regular" sandcastles.
- Now build a sandcastle with layers of window screen. First, pack about 1–2 inches of sand into the bottom of your bucket. Do not fill the entire bucket yet.
- Cut a piece of window screen that will fit inside your bucket (Figure 3).
Figure 3. Piece of window screen ready to place in the bucket.
- Firmly press the piece of window screen onto the layer of sand in the bucket (Figure 4).
Figure 4. Window screen inside the bucket.
- Repeat this process, adding a new 1–2 inch layer of sand and then another piece of window screen, until your bucket is full. Make sure you firmly pack down each layer.
- Repeat steps 2–6 with your new type of sandcastle. Note: It may be more difficult to get this sandcastle out of the bucket. If you cannot get it out in one piece, you might need to re-pack the sand after trimming the edges of the window screen pieces slightly.
- Repeat the process two more times, for a total of three trials with the sandcastles with window screen.
- Calculate an average number of bricks for each type of sandcastle. To calculate an average, add together the number of bricks for each trial, then divide by the number of trials. For example, if you did three trials and your sandcastles held three, four and five bricks, then the total is 12. Divide that by three to get an average of four bricks.
- Compare your results for the two types of castles. You might want to make a bar graph showing your results. Which type of castle held more weight? Does this match your prediction?
Ask an Expert
- Try changing the spacing of the window screen layers in your sandcastle. What happens if you space them 3–4 inches apart? What happens if you only add one window screen layer in the middle of the bucket?
- How tall can you make a sandcastle tower before it collapses under its own weight? Does adding layers of window screen help make it taller?
- Can you make a sandcastle strong enough for a person to stand on?
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