Hands-on Activity: Simple Snow Load Roof Model Demo: Which Roof Is Tops?

Contributed by: Center for Engineering Educational Outreach, Tufts University

A wide photograph of the view from the top of Giotto's Campanile shows the various terracotta roof top shapes in Florence, Italy.
Look at all the different roof top shapes!
copyright
Copyright © 2011 Darren Po, Wikimedia Commons CC BY-SA 3.0 https://commons.wikimedia.org/wiki/File:Florence_rooftops.jpg

Summary

When you look around your neighborhood, what do the roofs look like? What if you lived in an area with a different climate, how might that affect the style of roofs that you see? Through this introductory engineering activity, students consider the advantages of different roof shapes for different climates or situations. During a teacher demo, they observe and discuss what happens when a "snow load" (sifted cups of flour) is placed on three different model roof shapes. A student worksheet is included.
This engineering curriculum meets Next Generation Science Standards (NGSS).

Engineering Connection

Civil engineers always consider the climate of the area in which they plan to design and build structures. The design and materials chosen for a building's roof help to maintain the desired temperature within the building and provide a stable structure to protect against the local weather conditions. Engineers use models to test the shapes, materials and functionality of their designs.

Learning Objectives

  • Materials both natural and human-made have specific characteristics that determine their suitable use.
  • Engineering design requires creative thinking and consideration of a variety of ideas to solve practical problems.

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Educational Standards

Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.

All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).

In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.

  • Analyze data from tests of two objects designed to solve the same problem to compare the strengths and weaknesses of how each performs. (Grades K - 2) Details... View more aligned curriculum... Do you agree with this alignment?
  • Develop a simple sketch, drawing, or physical model to illustrate how the shape of an object helps it function as needed to solve a given problem. (Grades K - 2) Details... View more aligned curriculum... Do you agree with this alignment?
  • Identify and describe the safe and proper use of tools and materials (e.g., glue, scissors, tape, ruler, paper, toothpicks, straws, spools) to construct simple structures. (Grades Pre-K - 2) Details... View more aligned curriculum... Do you agree with this alignment?
  • Demonstrate that the way to change the motion of an object is to apply a force (give it a push or a pull). The greater the force, the greater the change in the motion of the object. (Grades Pre-K - 2) Details... View more aligned curriculum... Do you agree with this alignment?
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Materials List

Three side-view line drawings show simple curved, A-frame and flat roof shapes.
Figure 1. Three different roof shapes.
copyright
Copyright © 2004 Tufts University

  • 3 shoeboxes or similar containers
  • 1 poster board
  • 1 newspaper and/or cookie sheet
  • ~2 cups flour
  • (optional) flour sifter or sieve
  • Roof Shape Worksheet, one per student

Introduction/Motivation

What shape is the roof on your house? What is the climate where you live? Can you think of reasons why the climate might influence the shape of your roof?

Imagine you live in an area that receives a lot of snow. Architects and engineers who design homes in regions that get a lot of snow think about how snow builds up on the roofs. If a roof is not strong enough, the weight of the snow (the "snow load") may cause the roof to cave in.

If you were an engineer designing a roof for a snowy climate, what roof shapes would you consider to prevent snow from building up on the roof? What types of materials would you use to build your roof to help prevent snow from sticking to it?

Procedure

Background

A model is a copy of an object that is too big, too small or too complicated, costly or dangerous to study easily. Engineers use models to test and study how well things are built or to test different designs. To an engineer, a  "load" is any force that pushes or pulls. For example, the weight of snow pushes down on a building, and that's what we call a snow load. A wind load pushes on the sides of a building and the structures of a bridge.

Before the Activity

  • Gather materials. Obtain flour and containers to hold about 2 cups of flour. A flour sieve is helpful, if available.
  • Make copies of the Roof Shape Worksheet, one per student.
  • Gather a collection of photographs from the Internet that show different types of roofs in various climates to show the class.
  • Create three model roofs for a class demo. Cut away one end of each box so that students can view the effects of snow loads. Use poster board to make three different roof types, one for each box: curved, A-frame and flat (see Figure 1 or the worksheet). Using a single piece of masking tape, tape each edge of the roof to the open top of the box. Place newspaper and/or a cookie sheet under the testing station to catch any loose flour (to control the mess and collect flour to use again in the next test).

With the Students

  1. Show the class photographs of different roof designs. Talk about what types of climates each roof might be found in. What characteristics make a roof good or bad for a given climate? Incorporate the Investigating Questions into the activity.
  2. Show the class the example roofs you prepared in advance. We call these models. 
  3. Explain that the flour represents snow. Ask students to make predictions as to which roof would be best for a snowy climate.
  4. Slowly sprinkle "snow" onto the center of the roof as students watch the roof through the open end of the box.
  5. Have students make observations on their worksheets as the snow is applied to the roof and builds up to a weighty amount ("the snow load").
  6. Repeat the process with each model roof type.
  7. Conclude with a class discussion to share and compare observations and conclusions. Refer to the Investigating Questions.

Attachments

Troubleshooting Tips

To avoid a flour storm after done loading one roof type, carefully lift the roof and gently tap the bottom so that the flour falls into the box. Empty the flour from the box into a container to be reused for the next test.

Investigating Questions

  • Predict: Which roof type will cave in to the snow load the easiest? Why?
  • What happened to each model roof when a snow load was applied?
  • Does the "snow" pile up or slide off? Is this different for different roof types?
  • Which roofs sag? What does the sagging mean?
  • Which roofs fall down? Do they fall slowly or all at once?
  • Which roof design is "tops" for snowy climates?
  • In addition to snow loads, what other forces should we plan for? (The forces of wind and rain and maybe even earthquake shaking; weight of shingles or tiles plus gutters and walking people; falling tree branches.)
  • Which roof shaphe would you want if you lived in a snowy area? A windy area? Rainy?
  • What roof styles, shapes and materials are best for which climates and weather conditions?

Assessment

Questions: Throughout the activity, ask students the Investigating Questions to gauge their comprehension of the concepts. Refer to the Rubric for Performance Assessment for suggested criteria to assess their knowledge and understanding of the concepts.

Copyright

© 2013 by Regents of the University of Colorado; original © 2004 Worcester Polytechnic Institute

Supporting Program

Center for Engineering Educational Outreach, Tufts University

Last modified: March 1, 2018

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