Roofs and Vents Lesson Plan
CLASS:
Roofs and Vents
COURSE:
Tactical Diagramming
DATE PREPARED:
PREPARED BY:
February 10, 2010
Charles “Sid” Heal, MS, MPA
DATE REVISED:
REVISED BY:
TIME ALLOTTED:
2 Hours
INSTRUCTOR(S):
List name(s)
METHODS OF INSTRUCTION:
PowerPoint presentation, lecture, moderated discussion,
practical application—self-test
MATERIALS:
Laptop computer, LCD projector, overhead
projector/blackboard or white board, handout materials,
pencil and eraser for each student, tables & chairs in
sufficient number, suitable room for given class size
REFERENCES:
An Illustrated Guide to Tactical Diagramming, Heal, Sid,
Lantern Books, New York, New York, 2006
INSTRUCTIONAL GOALS:
Describe the six most common roof styles in North
American housing and the advantages and disadvantages of
each in determining floor plans
Explain the significance of vents protruding through a roof
above interior walls and how it aids in tactical
diagramming
Explain how vent patterns can not only reveal a floor plan
but identify other structures with the identical floor plan
even if when it uses a different style of roof
1
PERFORMANCE OBJECTIVES:
At the conclusion of this block of instruction, the student
will be able to:

Understand and describe the six most common styles of
roofs in North American houses and the two that
predominate

Explain which roof styles are commonly used to cover
houses that have living spaces above the first floor

Identify and describe the distinguishing features of the
two types of vents that provide the most reliable
information for tactical diagramming

Describe and explain the significance of vents installed
in interior walls and how it aids in determining floor
plans, to include fixtures, appliances, and doors

Demonstrate a thorough understanding of how roofs,
vents and ducts can be used to determine floor plans
with a self-test practical application focused on the
training objectives of this class
2
Roofs and Vents Outline
I.
II.
Introduction
A.
Instructor Introductions
B.
Describe the class goals and performance objectives
C.
Explain the importance of being able to identify the various roof styles and why
they aid tactical diagramming
D.
Explain why some roof styles are better for some types of use and climates than
others and how this assists in determining living spaces and floor plans
E.
Explain the significance of vents and why this class will emphasize an ability to
identify the two most useful for determining floor plans and why
Roof Styles and Dormers
A.
Roofs are one of the most conspicuous features on any building
1.
Some roofs are characteristic of what a building is used for
2.
Roofs contain features that can identify walls, types of rooms, areas of a
house and so forth
3.
Roof styles are often used to change the appearance of a house without
changing the floor plan
4.
B.
a)
Often used in tract homes to enable a single or few floor plans
throughout the tract without having all the houses appear identical
b)
Tremendously enhances an ability to diagram because features on
one structure can be used to predict floor plans on another
Roof profiles in general
a)
All roofs are slanted, no exceptions
b)
The pitch of the roof can identify living spaces under it
c)
Color and shape of a roof can identify additions and remodeling
after the original structure was completed
d)
Vent patterns are diagnostic in identifying identical floor plans on
other structures, often great distances away
e)
The use of aerial photographs greatly facilitates diagramming
when using features that are more visible from above than on the
ground
While roofs take on many profiles only six are typically used for houses in North
America
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1.
2.
Gable Roofs are the most popular roof for housing in America
a)
A 4-12 pitch is most common in warmer climates
b)
A 6-12 pitch or greater is used in colder climates to avoid snow
accumulating and sitting on the building
c)
The steeper the pitch the greater space there is under the roof
(1)
While this space may be used for storage or to install
heating and air conditioning vents and appliances, it is also
likely to be used as a living space, most often a sleeping
area
(2)
The 45 rule states that whenever a roof has a pitch of 45° or
greater suspect the presence of a living space under the roof
(3)
This diagramming principle holds true regardless of the
roof style
Roof nomenclature
a)
While there are many components of a roof, three are used so often
in diagramming that they need to be understood
(1)
Ridge or Peak—the highest portion of a roof. The ridge
may be thought of as the “spine” of a roof and the
significance will be discussed in this class and others
(2)
Gable—the gable is the triangle portion under the eaves at
each end of a roof and any wing or protrusion.
(3)
Eave— The overhanging lower edge of a roof. Eaves are
the lowest part of a roof.
b)
One other component useful for tactical diagramming is the
material since a change in style, color or type of roofing is frequently an
indicator of an addition or remodel
3.
Hip roofs are the second most popular roof style in North America
a)
Arguably, hip and gable roof styles and their combinations on the
same structure, account for more than 90% of all houses in the
United States
b)
Hip roofs are similar to gable roofs except that gables are “tipped
in” so that they are actually part of the roof
(1)
Most of the time hip roofs will also have a ridge line but on
a square building it is possible to have all four sides come
together at a single point. In this case the roof will have a
peak but no ridge.
4
c)
4.
Hip roofs are popular in high wind areas because they
present a lower profile and are less likely to be lifted from
the structure
(3)
Hip roofs are also popular in hot climates because they
have a reduced attic area that will hold heated air and
radiate heat into the living spaces
Most hip roofs will not have a living space underneath them
(1)
Steep hip roofs are sometimes used in more luxurious
homes
(2)
Steep hip roofs can sometimes cover a living space but
when this configuration is used other architectural features
will also be present, especially dormers and windows
Shed roofs are most often used for out buildings but on houses they are
popular for covering patios, porches, carports and garages.
a)
5.
(2)
A shed roof is often called a “flat roof” because of the shallow
pitch, often as shallow as 1-12 or 2-12.
(1)
All roofs have a pitch, to include shed roofs to avoid water
sitting on the roof and adding weight or creating a greater
potential for leaks
(2)
Shed roofs are very conspicuous because they must use
“rolled roofing” instead of shingles.
(3)
Shed roofs are also very common over additions
b)
Shed roofs virtually never have a living space under them because
of the reduced attic space.
c)
Visible vents and ducts protruding through a shed roof are nearly
always directly over the appliance they serve because there is no
room to move them in the attic area
A gambrel roof is so often used on barns that it is just as often called a
“barn roof.”
a)
Gambrel roofs have two different pitches on the same roof slope.
The first is very steep, often 8-12 and even steeper, with a much
flatter pitch near the top
b)
While gambrel roofs are popular for barns they are not uncommon
for housing
(1)
Gambrel roofs are popular where heavy snow and rain are
probable
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(2)
c)
6.
7.
Gambrel roofs are also popular where zoning requirements
limit the height of buildings
When a gambrel roof is identified on a house it is nearly certain
that there is a living space under the roof, most commonly a
sleeping area
(1)
When diagramming a house with a gambrel roof consider
the “attic” area as a second-story
(2)
Look for dormers, windows, vents and other indications to
confirm the use of the area under the roof because they are
always present when the area is used as a living space.
A mansard roof is used for housing in some parts of the country.
a)
A mansard roof is sometimes called a “French roof” after the
Frenchman who invented it, Francois Mansart.
b)
Mansard roofs are not as popular for housing as the gable or hip
styles but are used often enough that they can’t be ignored.
(1)
Mansard roofs are more commonly used for small retail
and commercial buildings
(2)
When discovered on a house suspect an older style of
house, especially the large Victorian style of housing built
during the industrial age
c)
Mansard roofs are to a gambrel roof what a hip roof is to a gable
because the “ends” are tipped in but with two pitches on each side
d)
Mansard roofs nearly always contain a living space above the first
floor and directly under the roof.
(1)
Coupled with vents and dormers, a mansard roof would be
diagnostic of a second-story
(2)
The rooms under a mansard roof in a house are almost
always bedrooms
Monitor roofs are sometimes used in sunny climates
a)
A monitor roof has one roof plane higher than the other and so a
short wall connects the two roof ridges.
(1)
The higher roof plane is usually oriented toward the street
or front side of a house and is used to hide vents, air
conditioning, solar panels and other appliances
(2)
Just as often the short wall is full of windows to allow
natural lighting inside the structure.
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C.
Monitor roofs nearly always cover rooms with cathedral
ceilings; that is the ceilings are installed directly under the
roof without an attic
(4)
Houses with monitor roofs tend to be upscale and large
b)
Observation from above a monitor roof is especially critical for
tactical diagramming because of the impossibility of observing
vents, skylights, and so forth from the ground
c)
Monitor roofs may have a living space under the higher roof plane
and so observation of vents and windows is especially important
Dormers
1.
2.
III.
(3)
A dormer is a framed structure that projects from a roof surface to add
space, light and ventilation to an attic area.
a)
Dormers come in many styles but only two are very common.
b)
Dormers are identified by the style of roofing they use; these are
gable dormers and shed dormers
Some dormers are merely decorative but they are more expensive to build
and maintain than just a roof
a)
Shed dormers are nearly conclusive by themselves that they cover
a living space, most often a bedroom
b)
Dormers of either type with windows in them are nearly diagnostic
that they serve a living space
c)
Dormers, especially shed dormers, are frequently added during
remodeling to create space above the first floor for a living area,
most often a bedroom
Vents and Ducts
A.
Vents are used to get rid of smelly odors, carbon monoxide, cooking oils, fumes
and the like.
B.
Ducts are used to move conditioned air throughout the house
C.
Whenever possible, both vents and ducts are hidden from the living spaces of a
residence in soffits and even more commonly in walls
1.
Because of the prevalence of vents and ducts using interior walls to hide
them they are extremely useful for tactical diagramming when they
protrude above the walls
2.
A knowledge of what a vent and/or duct is used for and how to recognize
it then becomes useful for tactical diagramming
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D.
While there are many types of vents and ducts in a house, two are particularly
useful for tactical diagramming.
1.
A water appliance vent is used anywhere there is a drain
a)
Sinks, tubs, showers, and toilets all require water appliance vents
b)
The water appliance vent is simply a pipe that allows air to escape
from a drainage system.
c)
(1)
Without these vents (or when they are plugged) drains
gurgle and make noises
(2)
It is also possible to stop up a drain entirely when these
vents become plugged and so in areas of the country where
snow accumulates on roofs building codes require them to
protrude above the roof sufficiently to avoid being covered
with snow
Water appliance vents are easy to identify and hard to find
(1)
(2)
(3)
They are the smallest on the roof
(a)
Typically, a water appliance vent is simply a 1½
inch pipe protruding through the roof about one
foot.
(b)
They are never capped since they are directly
connected to a drain anyway
They are often painted to match the roof and so are even
less conspicuous
(a)
In identifying a water appliance vent it is often
useful to look for their shadows
(b)
The best time and place to observe and photograph
water appliance vents is from above and when the
sun is low to maximize
Water appliance vents are extremely reliable for identifying
internal walls because they commonly protrude through a
roof directly above them
(a)
The single exception is when a “stack vent” system
is used.
(i)
A stack vent system is when more than one
vent exhausts through a single pipe.
(ii)
Building codes require larger diameter pipes
when a stack vent system is used and so they
are fairly easy to distinguish between them
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(iii)
d)
2.
Stack vents will nearly always protrude
through a roof near a ridge, often behind it
for aesthetic reasons
(b)
The more vents that protrude through a roof the less
likely a stack vent system is used
(c)
The closer to the eaves and the flatter the pitch of
the roof the more likely the vent is directly above
the wall hiding it. Moreover, it is nearly always
directly above the appliance/drain it serves.
Water appliance vents are the most useful for tactical diagramming
(1)
A typical house may have four or five and even more, each
of which is directly over an interior wall and the
appliance/drain it serves
(2)
An aerial photograph directly above a location may allow
“connecting the dots” by simply observing the water
appliance vents and then estimating the interior walls as
perpendicular or parallel to the exterior walls
(3)
Vents used in conjunction with other architectural features,
especially windows, can even determine where bathroom
fixtures and doors are or can’t be
The other vent useful for tactical diagramming is a combustion vent
a)
Combustion vents serve appliances that burn, such as a furnace,
central heating and/or gas water heaters
b)
Combustion vents are normally not in walls but in spaces and so
are not as precise as water appliance vents
(1)
(2)
A knowledge of where a water heater is very valuable for
identifying a kitchen since the sink is nearly always within
25 feet and often closer
(a)
Electrical water heaters do not need a combustion
vent
(b)
Upscale houses may have more than one water
heater. If so, the second one is normally in
proximity to the master bath.
The presence of combustion vents in some roofs is
particularly poignant for tactical diagramming
(a)
Garages are sometimes converted to living spaces
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(b)
(3)
Combustion vents are usually the largest vents on a house
(a)
The vent pipe is usually at least 4 inches in diameter
and sometimes larger
(b)
Older construction may have clay or asbestos pipes
but all modern houses will use a double or triplewalled galvanized steel tube
(c)
3.
(i)
Like water appliance vents, these vents are
frequently painted the color of the roof to
make them less conspicuous
(ii)
Combustion vents typically protrude from a
roof two feet or more.
These vents always have a cap to keep precipitation
away from the combustion appliance
Vent patterns might be compared as a kind of “fingerprint” for a house
a)
While a vent pattern is not unique to a particular house they are to
a particular floor plan
b)
When a vent pattern is repeated on another structure the features
from that building can be used to assist in diagramming the other
c)
The buildings may not appear similar
d)
IV.
Outbuildings with combustion vents, especially in
warmer climates, should create an assumption that
the building is being used as a dwelling and a good
diagrammer will try and confirm suspicions.
(1)
Identical and reverse floor plans are common in tract
houses
(2)
Builders and architects disguise the appearance of houses
with identical floor plans by changing their orientation,
style of roof, siding and landscaping
(3)
In some cases the buildings may not even be in close
proximity to another
The cardinal rule of diagramming—as the number of details you
use to predict the location of inside features increases, so does the
degree of reliability and precision of your diagram
Review and Evaluation
A.
Review and quiz students on the concepts and terminology of the class
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B.
Have the students work through the practical application by answering the
questions on the provided graphics
1.
There are a total of twenty questions regarding eleven situations, each with
either a graphic or photograph depicting a factor specifically related to
roofs and/or vents.
2.
Each of the questions is designed to focus a student’s attention on salient
features that can be used to reliably determine a building’s floor plan.
C.
Review the material with the students and ensure their understanding by asking
for their assessments and supporting rationale
D.
Refer to performance objectives and encourage personal examples
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