SHPE Jr. Chapter April 2015 STEM Activity
Instructor resource
A Waterproof Roof
Students design, build, and test a waterproof
roof. They learn about roof styles and
shapes, and consider materials and shape
when constructing a roof with a goal to make
the roof waterproof.
Learning objectives
• Learn about structural engineering
• Understand the role an engineer can
play in designing a house and
working with an architect
• Learn about hydrophobic properties
of materials
• Predict and experiment with how
different roof shapes and materials
conduct water flow
(Image: Imgarcade)
Engineering/STEM areas:
Civil engineering, structural engineering, physics, materials science
Materials
• Student Resource Sheets (in lesson)
• Student Worksheets (in lesson)
• A large bin (planter box, kitty litter box, etc. or sink for testing roofs
• Building materials such as leaves, grass, cotton balls, paper towels, string,
paper clips, cardboard, tape, newspaper, wooden dowels, branches,
shells, nuts, pipe cleaners, non-water proof fabric, wax, oil. Foil or plastic
pieces should be no larger than 4x4 square cm.
• Measuring cup
• Towels
• For each pair or team:
• An empty milk carton (preferably a half gallon)
• 1 L of water for testing the roof
Time required
60 mins
Suggested group size:
3-4 depending on number of students
Preparation
1. Read through both the student and instructor resources so you have the
background information
2. Gather all the necessary materials.
3. Add information about available building materials to the Student
Worksheet
4. Make enough copies of the Student Resource so that each student has
one
5. Make one copy of the Student Worksheet per group, plus a few extras
6. Design and build your own roof that you can show as a demo
Procedure
1. Ask students to think about the roles a roof plays in a house. It keeps
water out. It regulates heat. It can provide a decorative appearance.
Explain that the appearance of a roof is the job of an architect. Engineers
and architects sometimes work closely together to design a roof that is
both attractive and works well.
2. Ask students to imagine they had to build a new roof for their home but
they had to use only materials they could collect from their environment.
What materials they would use? They can collect things from parks,
forests, the earth, and public spaces. Stealing roofing materials from a
hardware store is not allowed! Go over the Student Resource and make
sure that students understand the assignment and the parameters to
consider (cost of materials, manufacturing, client’s needs, etc.)
3. Introduce the activity and go over the information in the Student Resource
and emphasize how roof structure and materials need to be suited to the
climate and elements. Tell students that they’ll play the roles of both
architect and engineer.
4. Place students in groups of 3-4 and give each group a milk carton. Tell
them they have about 10 minutes to sketch a roof design and choose
materials from the list on the worksheet. Let them know that the roof will
have to withstand a liter of water “raining” on it.
5. After ten minutes, invite students up to gather the materials they’ll use.
Give students about 20 minutes to build their roofs, and warn them when
they have only five minutes left.
6. While students are working, lay towels out near the testing bin or sink (this
won’t be necessary if you can work outside)
7. Have students bring all their houses to an area near the testing bin or sink
(or outside, if that’s possible). One by one, place each house in the testing
bin, slowly pour 1L of water over it. Take the house out of the testing bin
carefully without tilting it, and set it aside on the ground or on a towel.
8. Each group should take about five minutes to complete the reflection
questions. After they’ve finished their questions, they should check inside
their houses and see how much water, if any, has leaked through the roof.
9. Groups report out on the success of their roof and propose improvements
if necessary.
Assessments
Each group should describe the following to other students:
 Whether their design resulted in a waterproof roof
 How well their original design and materials list matched their final
product. If they made changes to either or both, explain why.
 What they think worked best about their design and why
Extensions
•
Students learn about the design of green roofs, and to propose how they
might change their roof design to make it into a green roof.
If students have access to the internet, you could choose to make this
activity one about green roof design rather than waterproofing. Students
would only be able to make sketches, but they should describe how their
roofs would regulate heat and conserve water usage. The AAAS “Green
Roof Design” is a good starting point:
http://sciencenetlinks.com/lessons/green-roof-design/
•
Students apply what they know about trusses (see Feb activity about
bridges) to design trusses that would allow the roof to hold significant
weight.
•
Students become familiar with the hydrophobic effect and the structure of
hydrophobic nanomaterials. One new substance called liquid glass is
being sprayed on roof tiles to make them superhydrophobic.
http://phys.org/news184310039.html
Resources/Bibliography
Windows, Doors, Roofs, and Housing Styles
Utah Education Network
http://www.uen.org/Lessonplan/preview.cgi?LPid=5079
Waterproof That Roof!
Try Engineering
http://tryengineering.org/lesson-plans/waterproof-roof
How to Choose a Roof for Your Home
Today’s Homeowner
http://www.todayshomeowner.com/choosing-a-roof/
Roof Designs and Styles
BUILD
http://www.build.com.au/roof-designs-and-styles
April 2015 SHPE Jr. Chapter STEM Activity
Student Resource
A Waterproof Roof
Having a roof over your head is an important part
of having a place to call home. But if that roof also
leaks on your head, it makes your home a lot less
comfortable. Putting together a roof that’s going to
last for many years requires taking many factors
into consideration. Among them are:





How long do you want the roof to last?
How much money do you want to spend on
the roof?
What type of climate is the house in? Hot?
Dry? Humid? Variable?
Is the frame of the house strong enough to
support heavier roofing materials?
What type of roof best complements the
house aesthetically?
Engineers work with architects and homeowners to answer these questions.
Sometimes engineers and architects collaborate directly, and other tim
es the architect designs some aspects of the house and its roof and the engineer
is responsible for determining how it will come together.
When designing a roof, there are two main decisions to be made. What shape
will the roof have? And what will it be made of?
Roof shapes
The shape of a roof can have a huge effect on the appearance of a house. The
shape of the roof also has to accommodate the weather elements. In a snowy or
rainy climate, you want a steeper roof that lets precipitation slide off. In a drier
climate, you can get away with a flat roof, which doesn’t require extra attic space.
Here are some common roof styles:
A gabled roof is one of the simpler roof shapes. It’s distinguished by the way the
roof goes from a peak to the eaves (where it meets the house). The slopes that
form a gabled roof will make a symmetrically triangular shape when you look at
the building from the side.
Advantages:
• Inexpensive
• Allows extra room for an attic
• The slope allows rain and snow to
slide off
Disadvantages:
• Not as stable in strong winds
• Requires creation of extra space if
not interested in an attic
• Steep angles can make the roof
harder to repair than other types
The design of a hip roof will have four sides, rather than two, with each side
sloping down toward the wall below it. The slopes of a hip roof can extend past
the walls of the house on all sides, making it a good roof type to provide shade.
Advantages:
• Can withstand strong winds
• Slope allows rain and snow to slide off
Can provide shade
Disadvantages:
• Lower roof peak means less attic space
• More expensive than gabled roof
The simplest roof type of all is a flat roof. It’s just like it sounds: flat, though most
flat roofs have a very slight angle to them.
Advantages:
• The most inexpensive to install initially
• Don't require the creation of attic space
• Can be used as an outdoor space
• Easy to access for repairs
Disadvantages:
• Not as durable as other types of roofs
• More difficult to waterproof and prone
to water damage
• Not stable in high winds or storms such
as cyclones
If you take the single plane of a flat roof, extend the edges beyond the walls of
the house, and give it a tilt, you’ve got a shed roof. Shed roofs can lend a
modern and minimalist look to a house.
Advantages:
• Inexpensive
• Good for draining precipitation
Disadvantages:
• Might leave low ceilings depending on
steepness of tilt and the size of the
house
• Less stable in windy conditions than
gable or hip roof
Roofing materials
Not only can your roof take many different shapes, but it can be made of many
different types of materials. In the United States, we commonly think of roof
materials as being shingles or tiles of some sort, whether they be wood or clay or
composite. But in some other parts of the world, you can find roofs made of
natural materials gathered from the environment. In northern Europe, parts of
Asia, and equatorial areas in Africa, for example, thatched roofs made from dried
vegetation are quite common.
Roofing materials can strongly effect the appearance of a house, and they also
serve an important part of its function in protecting against the elements. In areas
where wildfires or high-wind storms like hurricane and tornadoes are likely, you
need to choose a material that is fireproof or wind-resistant. And some materials
are much heavier than others, and not every roof can hold them.
Here are some roofing materials to compare:
Thatched roofs are an ancient as Bronze Age structures in Northern Europe.
Thatch is hand-made from vegetation. Usually the vegetation has been dried, but
in humid climates, sometimes items such as large leaves are used green and
mixed with reeds or other more fibrous materials. Thatch is often thought of as a
material used in developing countries, but thatching is becoming more popular in
places where people want to build structures from more sustainable materials.
Advantages
• Can be used on many different roof
shapes
• Can be collected from the local
environment
• Very long lasting. Repairs and
improvements involve adding more
thatch, rather than replacing a roof.
(Some buildings in England still have a
base layer of original thatching that dates
back 500 years.)
Disadvantages
• Expensive (in the U.S. and Europe)
• Must be coated to reduce fire danger
• A thatched roof may require a steeper
slope than other roofing materials in a
very wet or snowy climate
A thatched-roof house in England
Asphalt shingles are the most popular shingles in the U.S., probably because
they’re relatively affordable and quite versatile. Asphalt shingles come in a
variety of colors, and can be used on moderate and steeply sloped roofs.
Advantages:
• Can be used on many different roof
shapes
• Potentially eco-friendly if made from
recycles materials
• Fire resistant
• Inexpensive
• Lightweight
Disadvantages
• Doesn’t last as long as other roofing
types
• Made from petroleum products: not ecofriendly unless recycled
• Only fair resistance to wind
• May develop growths of algae unless
coated
A house with asphalt shingles
Clay tiles, while not as ancient as thatching, have been used for a very long
time. They can lend an Italian or Spanish flavor to a home’s appearance.
Advantages:
• Very fire resistant
• Long lasting (often lasts longer than the
frame of the house)
• Made from natural materials (kiln-fired clay)
• Can be used on moderate to steep sloping
roofs
Disadvantages
• Very heavy, roof frame must be able to
support it
• Expensive
• Poor wind resistance
• Brittle and may break when making repairs
Wood shingles can lend a home a rustic look. Because each wooden shingle is
unique, a wood shingle roof can have a lot of character.
Advantages:
• Made of natural materials
• Much lighter than tile
• Also helps to insulate roof
Disadvantages
• Doesn’t last as long as other roofing
types
• Rotted wooden shingles can’t be
recycled
• Must be properly treated for fire
resistance.
• More difficult to install than other
roofing types.
Metal roofing was very popular in the 1700s and 1800s, and you can see
examples of it on the Washington Monument and Thomas Jefferson’s Monticello.
Today, metal roofing often offers a modern look.
Advantages:
• Long-lasting
• Can be made from recycled materials and
recycled when replaced
• Fire and wind resistant
• Lightweight
Disadvantages
• More expensive than asphalt roofs
• Longevity of the roof depends on which
metal is used
• Can be noisy during rain or hail storms
• Must be carefully installed so that water
doesn’t accumulate and cause rusting
Apr. 2015 SHPE Jr. Chapter STEM Activity
Student Worksheet
A Waterproof Roof
Activity Procedure
In this activity, you’ll design and build a roof that can remain waterproof while
having a liter of water poured over it. As a group, you’ll need to consider:




The climate and elements in the environment of the roof
How different roof shapes direct water
How different roofing materials will direct water
Which combination of shape and materials is best suited to the
environment
Here are the building materials your instructor will have available for you:
(Instructor: ADD MATERIALS LIST HERE)
In the box below, make a list of the materials you’ll be using and the amounts you
think you’ll need. You may also want to make a sketch of your roof design.
Use your Student Resource to help you choose a roof shape and to think about
how to use your materials.
Build and test your roof
1) Put your roof together according to the roof shape you’ve chosen. It should fit
on top of your milk carton and cover it completely.
Your roof will need to remain waterproof as a liter of water is being poured on it.
2) When you’re done, bring your house with its roof to the testing area that your
instructor has set up.
3) Set you house aside for about five minutes to see if the roof leaks. In the
meantime, answer the question on the next page. You’ll use these answers when
you report on your results. When everyone’s roof has been tested, each group
will report on their results and explain their choices and any changes they made.
Questions
1) Explain your choice of materials? What advantages did they have over
materials you didn’t choose? How do your choices reflect what’s needed
in the climate you’re designing for?
2) Why did you choose your particular roof shape? How much importance
did you give aesthetics versus functionality?
3) Did you end up changing the shape or materials of the roof after you’d
done some work on the prototype? What problems did you encounter that
made you want to change your initial choices? How did your new choices
address those problems?