Introduction To Single-Ply
Objectives
When you complete this unit, you will be able
to:
 Explain what single-ply roofing is.
 Describe the advantages and disadvantages
of single-ply roofing.
 Look up the features of a single-ply material.
 Discuss the three factors that ensure your
safety.
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Single-Ply Roofing
Single-Ply roofing is any roofing system that
uses only one layer of roofing material instead
of built-up layers.
All single-ply systems must provide three basic
qualities:
 Waterproofing
 Strength
 Surface protection
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Waterproofing is provided by the roof membrane.
Strength is usually provided by a reinforcement
scrim (a mat of fiberglass, polyester, etc.)
embedded in the membrane.
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Scrim
Makes the membrane:
• Stronger
•Resists punctures
•Keeps it from cracking
•Helps the membrane expand and contract
•Improve appearance of the roof
•Hold down the membrane and insulation
•May be fire resistant
•May reflect heat
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MEMBRANE
The membrane is a sheet of single-ply roofing.
Different materials are used for the membrane.
Membranes should have these features:
 Good appearance
 High tensile strength
 Flexibility
 Long life
 Easy maintenance
 Installing single-ply
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Single-Ply Membranes
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Membranes must be able to:
Adjust to building movement.
Expand and contract with temperature changes.
Hold up under aging and temperature extremes.
Resist weathering.
Resist the effects of ozone and ultraviolet rays.
(Ozone is a form of oxygen that can be damaging.
Ultraviolet (UV) rays from the sun shorten the life of
the membrane.)
Resist becoming brittle at very low outdoor
temperatures.
Resist tearing.
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Defective Membrane
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Membrane Thickness
Membrane thickness may range from about 40
mils to 120 mils.
 The most common sizes are 45, 60, and 90
mils.
 A mil is 0.001" (one thousandth of an inch).
 Because membranes are relatively thin, mils
are easier to use than fractions of an inch.
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Membrane Thickness
The comparison below will give you an idea of
mil thicknesses:
 45 mils—Slightly over 1/32" (about as thick
as a dime)
 60 mils—1/16" (about as thick as a nickel)
 120 mils—Almost 1/8"
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Membrane Size
Membranes are usually applied in sizes as
large as is practical to handle.
This reduces the number of seams (which cuts
down labor costs) and reduces the chance of
leaks.
Common sizes are 6 to 50 feet wide and 100
feet long. Some membranes are up to 250
feet long.
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ADVANTAGES
Single-ply roofing has many advantages:
 May be lighter than built-up roofing. May
sometimes be laid over the existing roof,
avoiding the cost of removing the old roof.
 Easier to work with: Less material to haul up
to the roof. No hot bitumen and kettle to
handle. Fewer seams to seal.
 Expands and contracts more easily. Flexible
with temperature changes and movements of
the building.
 Attractive: Comes in different colors.
 Adapts to any shape of roof.
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DISADVANTAGES
Single-ply roofing has these disadvantages:
 Products and installation methods change
often because manufacturers are constantly
improving the products and methods.
 Some products are not yet time-tested.
 Some membranes are damaged by grease, oil,
asphalt, tar, etc.
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DISADVANTAGES
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Single-ply systems must be installed
exactly to specs.
The designer and the roofer must know what
materials will damage a product.
 Damage to a new roof by other crafts is a
constant problem.
 Some systems have to be installed at a
certain temperature range.
 Shrinkage can cause damage at base
flashings.
 Some membranes and materials have a short
shelf life.
(cont.)
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Single-ply systems must be
installed exactly to specs.
 Many solvents and adhesives are a fire
hazard or health hazard.
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Single-ply
Leaks are difficult to find, especially on
ballasted systems.
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Single-ply systems must be
installed exactly to specs.
 The system is unforgiving. The seams
are the only barrier against moisture, so
they have to be done right the first time.
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Wind & Air Pressure Dangers
Wind uplift has to be considered for any
single-ply roof.
 Manufacturers have ratings for how much air
pressure a roof system can withstand.
 Designers have wind speed maps that
give the fastest wind speed for an area. Roof
designs are based partly on this.
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Wind Map Speed
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Wind & Air Pressure Dangers
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Wind & Air Pressure Dangers
Other wind conditions have to be
considered.
 The taller the building, the more the speed and
direction of the wind on the roof can vary.
 The building location (for example, among tall
buildings or surrounded by hills) affects wind
patterns.
 The building structure, for example, the corners
of a roof have a high wind uplift because a
partial vacuum is created at the edge,
especially if there is a parapet wall. The higher
the parapet wall, the stronger the negative 22
pressure.
Wind & Air Pressure
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Wind & Air Pressure Dangers
Air pressure from below can also be a problem.
For example:
 A building has large overhead doors
 The doors are opened
 Air pressure rushes into the building
 This put pressure on the underside of the roof
membrane
 Enough air pressure raises the membrane
causing damage and leaks
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NRCA photos of roof damage from Hurricane Charley.
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MATERIALS
There are three categories of single-ply roofing
materials:
 Thermoplastics
 Modified Bitumens
 Elastomers
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ELASTOMERS
Elastomers have elastic, rubber-like qualities.
There are two types—cured and uncured:
 Cured elastomers cannot be formed. They
are generally used for the field membrane.
 Uncured elastomers can be formed. They are
generally used for detailing.
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Thermoplastics
A thermoplastic becomes soft when heated
and can be hot-air welded.
It can be reshaped as needed for detailing.
Hot-air welding fuses membranes together.
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Modified Bitumens
Modified bitumen's are asphalt sheets
modified with plastics or rubber.
Chemically, they are quite different from
elastomers or thermoplastics. However they
are generally classed with single-ply
membranes.
 Modified bitumen's are generally applied by
torch, hot asphalt or modified adhesives.
 Some are self-adhered (Peel & Stick).
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Surfacings
Surfacing may be applied in the factory or in the
field. Factory-applied surfacings may be such
things as:
 Liquid coating
 Embedded granulated minerals
 Laminated metal foil
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Surfacings
 Ballast (rock or pavers)
 Mineral granules
 Liquid coating
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Learning About Products
By visiting a manufacturers website you can
access information like:
 Systems: TPO, EPDM, BUR, PVC,
MODIFIES
 Details and Drawings
 Specifications
 Safety Data Sheets
 Videos and more
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Safety and Health
The most important subject in your training is safe
working practices.
If an accident leaves you handicapped or dead,
all your skill as a roofer means nothing.
And it can happen to YOU in one second.
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Safety and Health
 Roofing is one of the most dangerous trades.
 It is always among the ten industries with the
highest accident rates.
 The odds are against you unless you work to
change them for yourself.
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Safety and Health
Look at four other roofers on the job.
Statistics say that you or one of these four will be
injured on the job this year.
That is 1 in 5—very bad odds—and only you can
change them.
 We think of roofing in terms of falls and blunt
physical trauma but hazards come in various
forms.
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Hazards
 Falls
 Sprains and Strains
 Burns
 Electrocution
 Hit By Objects
 Fires and Explosions
 Noise
 Hazardous Substance
 Heat and Cold
 UV Danger
We will study roofing and waterproofing hazards
extensively through out your apprenticeship.
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Hazardous Materials
There are two important things to understand
about hazardous materials:
 The hazards vary considerably with different
products.
 Hazards can be short term (acute) or long
term (chronic). You may not notice any
effects when you are working with a
material, but you could be disabled from it 5,
10, or 20 years later.
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Safety Data Sheets
Review SDS to see what safety precautions are
needed.
 What type of PPE do I need.
 What if I get some on my skin or in my eyes?
 Is it flammable?
 How do I extinguish a product if it’s on fire?
 How should I store it?
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End of Chapter 1
Thank You
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